computer use

RTC Alarm

RTC Alarm is a hardware-level timing function controlled by the real-time clock (Real-Time Clock) on the motherboard. Even when the operating system is shut down or the hardware is in deep sleep, as long as the motherboard is still powered by battery or external power, it can trigger a signal to wake up the system at a preset time.

Core principles

The RTC chip contains a timer and an alarm register internally. When the value of the timer matches the target time (seconds, minutes, hours, and days) set in the register, the hardware will send an interrupt signal (Interrupt) to notify the power management unit (PMU) to perform a power-on action.

Main application scenarios

Scheduled startup: In the server or industrial computer, set a specific time point to automatically start.
Low-power devices: Microcontrollers (such as ESP32) enter deep sleep during data collection intervals and wake up regularly through RTC alarm clocks to save power.
System wake-up task: Windows schedules tasks to wake up the computer for execution, or Linux uses rtcwake for power management.

Operating system configuration method

platform	Setting method
Windows	Check "Wake the computer to perform this job" through the "Job Scheduler", or use PowerShell to manage Wake Timers.
Linux	Use instructions`rtcwake -m mem -s 60`(Represents waking up from memory sleep after 60 seconds).
BIOS/UEFI	Turn on Resume By RTC Alarm in the Power Management option and set a fixed time.

Effective conditions and restrictions

ErP mode: If the BIOS turns on extreme power saving (ErP Ready), the system will cut off the power supply to most circuits after shutting down, which may cause the RTC Alarm to fail.
Quick Start: The "Quick Start" function of Windows sometimes interferes with the hardware status, causing the scheduled boot after shutdown to fail.
CMOS battery: If the CR2032 battery on the motherboard is discharged, the RTC time will be reset after the system disconnects the external power supply, and the alarm clock will also become invalid.

Windows

Windows 11 shortcut keys

Win + D：Show desktop/recovery window.
Win + E：Open File Explorer.
Win + L：Lock screen.
Win + A：Open quick settings.
Win + N：Turn on notification center.
Win + I：Open settings.
Win + Tab：Open the task view, which displays open applications and virtual desktops.
Win + Ctrl + D：Added virtual desktop.
Win + Ctrl + left/right key:Switch virtual desktops.
Win + Ctrl + F4：Close the current virtual desktop.
Win + W：Open the gadget panel.
Win + PrtScn：Take a screenshot and save it to your pictures folder.
Win + Shift + S：Open the screenshot tool.
Alt + Tab：Switch open applications.
Ctrl + Shift + Esc：Open the job manager.
Win + Plus（+）/Minus（-）：Open and shrink the magnifying glass.
Win + H：Turn on voice input.
Win + K：Turn on a connected device, such as a wireless display or audio device.

PowerShell

What is PowerShell?

PowerShell is a cross-platform task automation solution, consisting of a command shell (Shell), a command code language, and a configuration management framework. Unlike traditional CMD, PowerShell is based on.NETConstructed, which handlesObjectsrather than a plain text string.

---

Core instruction structure: Verb-Noun

PowerShell commands (called Cmdlets) follow a "verb-noun" naming convention, making them very intuitive and easy to learn:

Get-Service: Obtain system services.
Stop-Process: Stop the executing program.
Set-ExecutionPolicy: Set script execution permission.
New-Item: Create a new file or folder.

---

Powerful pipe symbol (Pipeline)

In Linux Bash, pipes pass literals; in PowerShell, pipes pass completeobject. This means that subsequent instructions can directly access the properties produced by the previous instruction.

Example: Find the top 5 memory-consuming programs

Get-Process | Sort-Object WorkingSet -Descending | Select-Object -First 5

---

Common command comparison table

Function	PowerShell Cmdlet	Alias
list files	`Get-ChildItem`	`ls` / `dir`
Move directory	`Set-Location`	`cd`
copy file	`Copy-Item`	`cp` / `copy`
Show text	`Write-Output`	`echo`
Filter data	`Where-Object`	`?` / `where`

---

Advanced function: View object properties

If you want to know what information the object returned by a command contains, you can useGet-Member：

Get-Service | Get-Member

This will list all the properties and methods of the object, such as the serviceStatus, DisplayNamewait.

Execution script (.ps1)

By default, Windows restricts script execution for security reasons. To execute what you wrote.ps1Files usually require adjusting permissions:

Set-ExecutionPolicy RemoteSigned -Scope CurrentUser

How to display seconds in the lower right corner of Windows

Windows 10 / 11

By default, the time in the lower right corner does not display seconds, but it can be turned on through the registry.
The steps are as follows:

pressWin + R,enterregedit, press Enter to open the registration editor.

Navigate to path:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced

Right click to addDWORD (32-bit) value, named:
```
ShowSecondsInSystemClock
```
Double click and set to numeric value1。
Log out and log in again, or restart File Explorer (explorer.exe).

Quick way: Use PowerShell (System Administrator) to enter the following command:

Set-ItemProperty -Path "HKCU:\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" -Name ShowSecondsInSystemClock -Value 1
Stop-Process -Name explorer -Force

Windows 7

The system box time cannot display seconds through built-in functions or the registry.
Requires the use of third-party tools, such asT-Clock。

Download T-Clock (GitHub):https://github.com/White-Tiger/T-Clock
Unzip and executeClock.exeorTClock.exe。
Right click on the time in the lower right corner → SelectT-Clock Properties。
Enter in Time Format:
```
hh:nn:ss tt
```
Click Apply to display the time in seconds.

Time format example

Format	Display example
`hh:nn:ss tt`	03:45:12 PM
`HH:nn:ss`	15:45:12
`dddd, mmmm d, yyyy`	Monday, July 28, 2025

pagefile.sys virtual memory paging file management

1. What is pagefile.sys?

Function:pagefile.sys is a file used by Windows systems for virtual memory. When the physical memory (RAM) is insufficient, the system will temporarily store infrequently used data in this file.
Default position:Typically located in the root directory of the system disk (such as C:).
importance:Paging files are critical for the stable operation of applications with large memory requirements.

2. How to modify the path and size of pagefile.sys

Open system properties:
- according toWindows + Pause/BreakOpen System Properties, or right-click "This PC" and select "Contents."
- Click "Advanced System Settings" on the left.
Enter performance options:
- In the "System Properties" window, switch to the "Advanced" tab.
- In the "Performance" area, click "Settings."
Manage virtual memory:
- In the Performance Options window, switch to the Advanced tab.
- Click "Change" in the "Virtual Memory" area.
Set the paging file path and size:
- Cancel automatic management:Uncheck "Automatically manage paging file sizes for all disks".
- Select disk:Select the new disk for the paging file in the disk list.
- Set size:
  - Select "Custom Size".
  - Enter the "Initial Size" and "Maximum Size" in MB.
  - The recommended size is 1.5 to 3 times the physical memory size.
- Remove old disk paging files:Select the original disk and click "No paging".
Save and restart the system:
- Click OK and close all windows one by one.
- The system may prompt that a restart is required, select Restart now to apply the changes.

3. Precautions

Size recommendations:If the size of the paging file is too small, it may cause system instability; if it is too large, it will occupy disk space.
Select a fast disk:If optional, it is recommended to store paging files on SSD to improve performance.
Do not remove completely:Some applications may require paging files, and even if there is sufficient physical memory, it is recommended to keep them of a certain size.
Permission issues:Modifying tab settings requires administrator privileges.

4. Best practices for paging files

Set the paging file on a non-system disk to reduce the I/O burden on the system disk.
For multi-disk environments, paging files can be spread across multiple disks to improve performance.
Periodically check that the paging file size is sufficient, especially when running large applications.

View memory configuration

Method 1: Use Windows built-in tools

You can view the memory configuration through the Resource Monitor or command tools provided by Windows.

1. Use Resource Monitor to view

pressCtrl + Shift + EscOpen the job manager.
ClickefficacyPagination.
Select on the leftmemory。
Check the slot usage in the upper right corner. If there are multiple memories, "Slot 0", "Slot 1", etc. will be displayed.

For example:

If you see two slots showing 4GB each, it means there are two 4GB memories.
If you only see one slot showing 8GB, it means a single 8GB memory.

2. Use command prompt characters

Open the command prompt (pressWin + R,entercmdand press Enter).

Enter the following command to view memory information:

wmic MEMORYCHIP get BankLabel, Capacity, DeviceLocator, PartNumber

Review the output to confirm the memory slot and capacity.

Example output:

BankLabel      Capacity        DeviceLocator
BANK 0         4294967296      DIMM0
BANK 1         4294967296      DIMM1

This example shows two 4GB memory banks.

3. Use PowerShell

Open PowerShell (pressWin + R,enterpowershelland press Enter).

Execute the following command to view the memory:

Get-CimInstance -ClassName Win32_PhysicalMemory | Format-Table BankLabel, Capacity, DeviceLocator

View the results in a manner similar to command prompt characters.

Method 2: Use third-party tools

If you need more detailed memory information, you can use the following tools:

1. Using CPU-Z

Download and installCPU-Z。
Open the program and switch toMemoryPaging to view total capacity and channel mode (e.g. single channel or dual channel).
switch toSPDPaging, view the memory information of each slot.

2. Using HWiNFO

Download and installHWiNFO。
Select "Summary-only" mode to start, or click the "Memory" tab to view detailed information about each memory module.

Method 3: Check the physical hardware

If the above method cannot confirm, you can turn off the computer power and open the case to manually check the actual module number and label of the memory slot.

Summarize

Use built-in tools (Resource Monitor, Command Prompt, or PowerShell) to view slots and capacities.
Use third-party tools such as CPU-Z or HWiNFO to get details.
Check the actual configuration of the hardware if necessary.

Performance Monitor PerfMon

Performance Monitor (PerfMon for short) is a powerful tool built into Windows for real-time monitoring of system resources (such as CPU, memory, hard disk, network) and application performance data. It helps developers and system administrators diagnose performance bottlenecks or resource leaks.

How to turn on PerfMon

pressWin + Rkey, enterperfmonand press Enter.
Enter through "Control Panel" > "System Management Tools" > "Performance Monitor".

Core function module

Monitoring Tools: The default "Performance Monitor" chart can visually display the fluctuations of various performance counters (Counters) in real time.
Data Collector Sets: Allows users to customize collection rules and record performance data over a period of time into files (such as .blg files) for later offline analysis.
Reports: Automatically generate an analysis summary after data collection to help quickly judge the health status of the system.

Common performance counters (Counters)

Object	Counter	illustrate
Processor	% Processor Time	Overall CPU usage, if it continues to be higher than 80%, there may be a bottleneck.
Memory	Available MBytes	The amount of available physical memory. If the value is too low, the system will frequently swap paging.
Paging File	% Usage	Virtual memory usage can be used to determine whether physical memory is insufficient.
PhysicalDisk	% Idle Time / Avg. Disk Queue Length	Hard drive idle ratio or queue length, used to diagnose disk I/O latency.
Process	Private Bytes / Working Set	The memory usage of a specific program is detectedMemory Leakkey indicators.

Troubleshooting app

Detect memory leaks: Select a specific Process object and observePrivate BytesWhether it continues to rise over time and never falls back.
Diagnostic program stuck:observe% Processor TimeandThread Count, to confirm whether any specific threads enter a dead loop or are generated in large numbers.
Remote monitoring: PerfMon supports connecting to other computers in the domain, which is very useful for diagnosing server performance issues.

Differences from other tools

Task Manager: Provides an instant and simple overview, suitable for quick viewing, but lacks history and detailed counters.
Resource Monitor: Between the work manager and PerfMon, providing more intuitive file and network connection details.
PerfMon: The deepest and most professional, providing thousands of subtle indicators, suitable for performance analysis tasks that require accurate data.

lodctr

lodctr is a Windows built-in command line tool, mainly used to log in, update or repair the performance counter name and description text of Performance Monitor (PerfMon). It is the core tool for managing the association between system performance objects and application counter definition files (.ini).

Core functions and uses

Login new counter: When developers write services that support performance monitoring, use this tool to write defined counter information into the system login file.
Fix broken counter: Can be used to rebuild the counter list when the Performance Monitor cannot display a specific data category, or when numbers appear instead of text.
Backup and restore: Supports exporting the current counter settings for recovery when the system is damaged.

Common command syntax

Command example	Function description
`lodctr /s:backup.txt`	Back up the current performance counter settings to the specified text file.
`lodctr /r:backup.txt`	Restore performance counter settings from backup file.
`lodctr /r`	Most commonly used repair instructions. Automatically rebuild login information for all performance counters (requires administrator privileges to execute).
`lodctr <filename.ini>`	Install specific counter definition files.
`unlodctr <AppName>`	Remove performance counter settings for a specific application.

Common repair scenarios: PerfMon displays abnormally

If you see a "Unable to load performance counter" error message when launching Performance Monitor, or the counter name changes to a string of numbers, you can usually resolve it by following these steps:

bySystem administrator identityTurn on command prompt (CMD).
entercd %systemroot%\system32Enter the system directory.
implementlodctr /r. The system will attempt to repair all counters based on the backup file.
If you see the "Performance counter settings were successfully rebuilt" prompt, just restart the performance monitor.

Things to note

Permission restrictions: Since lodctr will be modified directlyHKEY_LOCAL_MACHINEFor sensitive login file keys under , you must have administrator privileges to execute any lodctr command.
bit version: On 64-bit Windows,System32andSysWOW64There are lodctr in all directories. If you are fixing counters for 32-bit applications, you should use the version under the SysWOW64 path.
interdependence:lodctr relies on properly formatted .ini files and .h header files. If the definition file itself is damaged, reloading it with lodctr alone will not solve the problem.

Computing performance test

Computing performance testing refers to using standardized algorithms or loads to evaluate the speed, stability and efficiency of computer hardware (CPU, GPU) or software systems when processing complex instructions. This type of testing is an important basis for optimizing code and hardware selection.

Core test indicators

Throughput: The number of tasks that can be completed per unit time, such as the number of transactions processed per second (TPS) or the number of floating point operations completed per second (FLOPS).
Response Time: The total time required from sending the command to getting the result, usually measured in milliseconds (ms).
Resource Utilization: When executing tasks, the occupancy ratio of CPU, memory and I/O is to achieve high efficiency rather than blindly full load.
Latency: Waiting time for instructions to be transmitted in the system or waiting for processing.

Common test types

Test type	Test purpose
Benchmarking	Use standardized tools such as SPEC or Geekbench to compare results to industry standards.
Stress Testing	Push the load to the limit and observe the system's crash point and resilience when resources are exhausted.
Load Testing	Run for a long time under expected high load to confirm whether the system can provide stable services.
Concurrency Testing	Simulate multiple users or multiple threads executing tasks at the same time, and check whether there are locks or race conditions.

Commonly used computing performance testing tools

CPU performance：
- Cinebench: Based on the Cinema 4D engine, test the rendering capabilities of the CPU.
- Prime95: Perform ultimate stress testing by finding the Mersenne prime number, often used to check overclocking stability.
System overall performance：
- PCMark: A comprehensive evaluation that simulates daily paperwork, video and content creation.
- Sysbench: A multi-functional command line tool that supports CPU, memory, I/O and database testing.
Development and code performance：
- BenchmarkDotNet: Sophisticated method-level testing tool for .NET developers.
- Pytest-benchmark: Python performance evaluation plug-in.

Best practices for testing

environmental isolation: During the test, irrelevant background programs (such as anti-virus software, update programs) should be closed to ensure that the results are not interfered with.
multiple sampling: There may be fluctuations in a single test, and the average (Average) and percentile (P95, P99) of multiple tests should be taken for interpretation.
Warm-up: Execute several tasks before formal recording to allow the CPU to enter the acceleration frequency and the cache to complete filling, so as to obtain data closer to the real situation.
Monitor thermal throttling: Pay attention to the temperature during the test. If the thermal protection (Thermal Throttling) is triggered, the test results will lose their reference value.

Windows Check CPU Temperature and Motherboard Temperature

Use BIOS to view

Restart the computer and enter the BIOS (usually pressF2、F10orDelete). CPU and motherboard temperatures can be viewed in hardware monitoring or system health status.

Using Task Manager

Currently, Windows' built-in job manager does not provide CPU temperature display, but it can view CPU usage and clock speed.

Using Windows PowerShell

You can try using the following PowerShell command to obtain temperature information (some systems may not support it):

Get-WmiObject MSAcpi_ThermalZoneTemperature -Namespace "root/wmi"

Use third-party software

HWMonitor- Free and powerful temperature monitoring tool.
Core Temp- A lightweight tool dedicated to monitoring CPU temperature.
HWiNFO- Provide detailed hardware information, including temperature monitoring.

Using the command prompt (CMD)

You can try the following command to check the temperature (some systems may not support it):

wmic /namespace:\\root\wmi PATH MSAcpi_ThermalZoneTemperature get CurrentTemperature

If the returned value is larger, you usually need to divide by 10 and subtract 273.15 to get the Celsius temperature.

Abnormal CPU usage and clock speed when the temperature is too high

CPU usage rises- When the CPU overheats, thermal throttling may occur, causing system execution efficiency to decrease and applications to take longer to complete calculations, thereby increasing CPU load.
CPU clock drops- In order to prevent overheating, the CPU will automatically reduce the clock speed to reduce heat generation, which may cause the system to slow down or even freeze.
Automatic shutdown or blue screen- If the temperature is too high and cannot be effectively lowered, the system may be forced to shut down or a blue screen (BSOD) may occur to protect the hardware from damage.

Check your motherboard model in Windows

Method 1: Using Command Prompt

Turn on command prompt characters:
- pressWin + R,entercmd, and then press Enter.
Enter the following command and execute it:
```
wmic baseboard get product,manufacturer
```

You will see output similar to the following:

Manufacturer      Product
ASUS              PRIME Z390-A

Method 2: Use PowerShell

Start PowerShell:
- pressWin + S,searchPowerShell, then execute as administrator.

Enter the following command and execute it:

Get-WmiObject Win32_BaseBoard | Format-Table Manufacturer, Product

You will see the manufacturer and model of your motherboard.

Method 3: Use third-party tools

If you need more detailed information, you can use the following third-party tools:

CPU-Z: Free tool to view detailed hardware information such as motherboard, CPU, memory, etc.
Speccy: Displays all hardware information with a friendly interface, suitable for general users.

Method 4: Check BIOS or UEFI

Restart the computer and press the specified key during startup to enter the BIOS/UEFI setup interface:
- Common keys includeF2、Deleteor other prompt keys.
Information about the motherboard model can usually be found in the BIOS/UEFI interface.

Change the file extension of the opener

Edit via File Explorer

Find the file you want to modify in File Explorer.
Right-click on the file and select "content」。
exist"generally” tab, click “change...」。
Select the program you want to use to open this type of file and clickSure」。
according to"Apply"Click again"Sure” Complete the setting.

Use "Open file method" to modify

Right-click the target file and select "Open file method」 > 「Choose another app」。
Select an application from the list. If it is not listed, click "More apps", or use "Find other apps on this computer」。
Check "Always use this application to open .extension files」。
Press "Sure” Complete the setting.

Modify via console

Open"console」 > 「Default application」。
Click "Select default application based on file type」。
Find the file extension you want to change, such as ".txt", and click the application name next to it.
Select a new application from the list, or browse to add a new executable.

Extension default program selection failed

Important preface

Windows 10 / 11 has "Extension Default Program"protection mechanism，
You can’t just change one machine code and it will take effect permanently., otherwise it will be automatically restored by the system. But there are still "feasible and stable" methods.

How Windows default programs actually work

.txt → ProgID
ProgID → actual execution program
UserChoice requires Hash (system verification)

Directly changing UserChoice without the correct Hash → will definitely fail

Method 1: Use ProgID (recommended, the most stable)

Step 1: Create a custom ProgID

Suppose you want to useNotepad++(Please adjust the path yourself)


Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\MyTxtEditor]
@="My TXT Editor"

[HKEY_CLASSES_ROOT\MyTxtEditor\shell\open\command]
@="\"C:\\Program Files\\Notepad++\\notepad++.exe\" \"%1\""

savemytxteditor.regand import

Step 2: Point the .txt to the ProgID


Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\.txt]
@="MyTxtEditor"

✔ This method is valid for "system level" ✔ Valid for new accounts and new files ⚠ Existing UserChoice may still overwrite

Method 2: Delete UserChoice (let the system apply it again)

This is the key step

Delete the following machine codes


HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.txt\UserChoice

After deletion:

Log out/restart
Windows will reuse the HKEY_CLASSES_ROOT setting

Method 3: Mandatory specification (only for testing, not guaranteed)

⚠ Windows may be restored in the next update


[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.txt\UserChoice]
"ProgId"="MyTxtEditor"

❌ No Hash, usually ignored or restored

Why does "Choose another app" fail?

Application did not register ProgID correctly
exe is not registered in App Paths
System cache is corrupted

Repair system cache (very useful)


taskkill /f /im explorer.exe
del /q "%LocalAppData%\Microsoft\Windows\Explorer\*.db"
start explorer.exe

Sysinternals toolset

Introduction to the toolset

Sysinternals is a free library of advanced system tools developed by Mark Russinovich and now maintained by Microsoft. It allows IT staff or advanced users to deeply explore, manage and troubleshoot the underlying operations of the Windows operating system. This set of tools is recognized as the "Swiss Knife" of Windows system diagnostics.

Core tool classification

The toolset contains more than 70 tools, mainly divided into the following categories:

File and disk tools:
- du: Query the directory disk usage.
- Diskmon: Monitor hard drive activity in real time.
- SDelete: Safely delete files (military-standard compliant, non-recoverable).
Network tools:
- TCPView: The graphical interface displays all network connections and endpoints in the current system.
- PsPing: Powerful network delay and bandwidth testing tool.
Process and performance monitoring:
- Process Explorer: Advanced version of the job manager, showing DLL, control points and CPU distribution.
- Process Monitor (ProcMon): Real-time capture of file system, login table and process activity.
Security and System Information:
- Autoruns: Lists all programs that will be automatically executed when the system starts (the most comprehensive startup management).
- Coreinfo: Display processor and cache topology.
- AccessChk: Quickly check the access rights of a specific user to a file or directory.

How to obtain and execute

A great feature of Sysinternals is that most of the tools areGreen installation-free, you can use it in the following three ways:

1. Official website download

Download the entire thing from Microsoft’s official websiteSysinternals SuiteZip file, or download the required tools separately.

2. Sysinternals Live (fastest way)

Microsoft provides a network share path that allows you to execute the tool directly without downloading it. In Windows File Explorer or CMD enter:

\\live.sysinternals.com\tools\du.exe
\\live.sysinternals.com\tools\procexp.exe

3. Install using winget

winget install Microsoft.SysinternalsSuite

Commonly used tools comparison table

Tool name	Function description	Applicable situations
Process Explorer	Replace job manager	Find out which program is hogging files and see what's causing your CPU spikes.
Autoruns	General inspection of startup items	Remove rogue software or check the cause of slow startup.
ProcMon	behavior monitoring record	The specific locations where the troubleshooter reports "Path Not Found" or "Access Denied" errors.
TCPView	Connection monitoring	See which programs are secretly connecting to the network.

Precautions for use

Administrator rights:Most tools (such asProcMon, Autoruns) needs to be "executed as a system administrator" to obtain complete information.
EULA Authorization:The authorization contract will jump out when the tool is executed for the first time. You can add it when using CMD./accepteulaParameters are automatically agreed.

microsoft.exe

What are Sysinternals du?

This is a disk usage (Disk Usage) tool officially provided by Microsoft and is part of the Sysinternals tool set. Its functionality is similar to that of LinuxduSimilar, but designed for the Windows NTFS file system and can handle it more accuratelySymbolic Links、Hard Linksas well asCompressed archive。

Download and install

Official download point: Sysinternals Disk Usage
Quick command line installation (using winget):

winget install Microsoft.Sysinternals.DiskUsage

Description of common parameters

parameter	illustrate
`-c`	Output results in CSV format (suitable for importing into Excel).
`-l <number>`	Specify the recursion depth (e.g.`-l 1`Only the first level of folders is displayed).
`-n`	Do not recurse into subdirectories (equivalent to only looking at the current level).
`-q`	Quiet mode, does not display banner information (Banner).
`-u`	Count the actual space occupied by "duplicate links".
`-v`	Shows size in KB.

Practical examples

1. Display the size of all first-level folders in the current directory

This is the closest to Linuxdu -h --max-depth=1Usage:

du -l 1

2. View a specific directory and output to CSV

If you need to log the scan results:

du -c C:\Users\YourName\Documents > usage.csv

3. Exclude banner information and view totals

du -q -s C:\Windows

Differences from Linux du

Path format:Supports Windows-style paths (e.g.C:\Windows）。
Unit display:The default is usually Byte or automatically adjusted according to the file size, but unlike Linux-hSo intuitive, it is usually recommended to cooperate with-vobserve.
Permission processing:Processing$Recycle.Binor system folder, it is still recommended to useAdministrator rightsExecute, otherwise Access Denied will appear.

Merge disk partitions

core logic

In Windows, to give space from slot E to slot C, these two partitions must be on the diskadjacent(Slot E follows slot C). Since Slot C is the system drive, it is recommended to follow the steps below. This does not require reinstalling Windows, but it is recommended to back up important data before proceeding.

Method 1: Use Windows’ built-in “Disk Management”

This is the safest method, but only if the E slot is empty since it needs to be deleted first.

pressWin + X,chooseDisk management。
Make sure there is no important data in slot E, and(E:)Right click and selectDelete disk volume。
After deletion, slot E will become "unallocated" space.
against(C:)Right click and selectExtend disk volume。
According to the wizard's instructions, merge all the space just released into slot C.

---

Method 2: Use third-party tools (no need to delete data)

If there is a lot of data in your E slot that you do not want to move, or if there is a "Recovery Partition" between the C slot and the E slot, the built-in tool will not be able to extend it. At this time, third-party tools need to be used for "non-destructive adjustment".

Recommended tools:AOMEI Partition Assistant or MiniTool Partition Wizard (free version is enough).
Operation steps:
1. Execute the tool and select the E slotResize/Move Partition。
2. Pull the left edge of slot E to the right to free up space on the right side of slot C.
3. Select against C slotResize/Move Partition, stretching the right border to the right.
4. ClickApply, the computer may restart and perform the move operation in Pre-OS mode.

---

FAQ: Stretched disk volume is gray?

If you delete the E slot but the "Extended Volume" of the C slot is still gray, it is usually because there is arepair partition. The processing method is as follows:

context	solution
There are other partitions between C and E	You need to use a third-party tool to "move back" the repaired partition so that the unallocated space is adjacent to the C slot.
E slot has not been deleted yet	The E slot must be deleted first and become "unconfigured" before the built-in tools can be extended.
The disk format is MBR and reaches the 2TB limit	Needs to be converted to GPT format.

Advanced tip: Use CMD (Diskpart) to delete a partition

If the disk management interface cannot delete some stubborn partitions, you can use the command:

diskpart
list disk
select disk 0 (confirm your SSD number)
list partition
select partition X (X is the number of slot E)
delete partition override

Handling Repair Disk Partition

Method 1: Use third-party tools (the simplest, lossless data)

This is the most recommended method because Windows built-in tools do not support "moving" partition locations. You can use free software such asAOMEI Partition AssistantorMiniTool Partition Wizard。

Install and start the tool.
You will see the layout:[C slot] [Repair partition] [Unallocated space]。
right clickRepair partition,chooseMove/Resize Partition。
Use your mouse to "drag" the box representing the partition to the far right.
At this point the layout will change to:[C slot] [Unallocated space] [Repair partition]。
ClickApplyand wait for restart execution.
Return to Windows Disk Management, right click on the C slot and clickExtend disk volume。

---

Method 2: Use commands to delete and repair partitions (advanced, manual recovery)

If you do not want to install third-party software, you can choose to delete the repair partition.Notice:After deletion, you will lose the built-in WinRE repair environment (if the system fails to repair automatically), it is recommended to create a USB boot repair disk first.

1. Deactivate the repair environment

Open CMD as administrator and enter:

reagentc /disable

2. Forced deletion and repair partition

usediskparttool:

diskpart
list disk
select disk 0 (assuming your SSD is disk 0)
list partition
select partition X (X is the number of the repair partition, usually about 500MB~1GB)
delete partition override

3. Extend C-slot

Now that the right side of the C slot is empty, just extend it directly in "Disk Management".

4. (Optional) Rebuild and repair the environment

If you want to keep the repair function, after extending the C slot, you can enter:

reagentc /enable

---

Plan comparison

plan	risk	advantage
Third party tools	Extremely low (error of operation may cause power outage)	Intuitive, no instructions required, retains repair function.
Diskpart Delete	Medium (lost built-in repair mode)	No need to install software, completely remove obstacles.

Windows Phone Connect Software

Phone Link

Windows built-in application, formerly known as "Your Phone"
Supports interoperability between Android phones and Windows computers
Can answer calls, view text messages, notifications, photos and apps
Required to be installed with Android devices"Link to Windows"app

Link to Windows

Android mobile application
Built-in in some models of Samsung and Xiaomi
Can be seamlessly integrated with mobile phone connection applications on Windows

AirDroid

Cross-platform file transfer and remote management tools
Supports wireless file transfer between Android and Windows
Can manage notifications, text messages, mirror screen and other functions

Pushbullet

Support push notifications between Android and Windows
Can send links, text messages and files
Supports Chrome browser extensions

Snapdrop

Open source, installation-free LAN file sharing tool
Instantly transfer files via browser
Easy to use across platforms, no account login required

Usage of Windows built-in mobile link

Preparation

The computer needs to be Windows 10 or Windows 11
The mobile phone needs to be Android version 7.0 or above
The computer and mobile phone need to be connected to the same Wi-Fi network

Step 1: Turn on mobile link on Windows

pressstart→ SearchPhone Linkand turn on
Click "Get Started" and select "Android" as the device type

Step 2: Install and configure "Connect to Windows" on your phone

Install on your phoneLink to Windowsapp
You can search and install it from the Google Play Store. Some Samsung and Xiaomi phones are pre-installed.
Sign in with the same Microsoft account as your computer

Step 3: Pair your phone and computer

Scan the QR Code on your computer with your phone or enter the code to pair
After the phone and computer are paired, it will show that the connection is successful.

Step 4: Get started

You can check mobile phone notifications and send text messages on your computer
Can answer/make calls directly (requires pairing via Bluetooth)
Can access mobile phone photos and application screens, and some devices support mirroring operations

Things to note

iPhone only supports some basic functions, such as calls and text messages
Different Android phone brands may support different functions.

WebCam

1. Basic functions of WebCam

video call:Suitable for scenarios such as meetings, online courses, and remote interviews.
Image shooting:Capture still images or record videos.
Facial recognition and security verification:Used to unlock the device or authenticate.
Image processing applications:Such as live broadcast, virtual background, changing special effects, etc.

2. Setup and installation

Built-in camera:Most laptops and all-in-one computers already have built-in cameras, and usually no additional settings are required.
External camera:
- Connect the camera to the USB port.
- Install the included driver, if not, the system default driver will be automatically installed.
Confirm running:
- Windows useCameraapplication.
- macOS usePhoto Boothor other image-enabled applications.
- Linux uses tools such asCheeseOr VLC Media Player.

3. Camera application software

Video conferencing tools:Such as Zoom, Microsoft Teams, Google Meet.
Video recording tools:OBS Studio, Camtasia or VLC Media Player.
Image processing software:Such as Snap Camera and ManyCam, used for virtual background and filter effects.

4. Tips for improving image quality

Light adjustment:Use in an environment with sufficient and even lighting, avoid backlighting or excessive brightness.
Resolution settings:Make sure the software supports high resolution and select 720p or 1080p image quality.
To clean the lens:Wipe the lens regularly with a soft cloth to avoid blurry images.
Stabilize camera position:Place the camera on a stable surface at eye level.

5. Security and privacy protection

Enable indicator light:Make sure there is an indicator light when the camera is turned on.
Use lens masking:Covers can be used to protect privacy when the camera is not in use.
Check app permissions:Only allow trusted applications to access the camera and check permission settings regularly.
Update software and firmware:Keep camera drivers and related software updated to prevent vulnerability exploitation.

6. Frequently Asked Questions and Solutions

Camera not working:Check connections, permissions and driver updates.
Blurred image:Clean the lens, adjust focus or change the lighting environment.
Unable to detect camera:Confirm that the camera is properly connected to the USB port and try a different port.

WebCam

Card reader shown but no smart card visible

If you can see the "Smart Card Reader" in Device Manager but not the smart card, it may be because the smart card is not recognized correctly or there is a problem with the driver. Here are some common workarounds:

1. Confirm that the smart card is inserted correctly

Confirm that the smart card has been correctly inserted into the card reader and that the insertion direction is correct. The chip side of the smart card needs to be correctly aligned with the contact point of the card reader.

2. Check the smart card reader driver

Make sure the smart card reader driver is installed correctly. Right-click "Smart Card Reader" in "Device Administrator" and select "Update Driver".
If the smart card still cannot be recognized after the driver is updated, you can reinstall the driver or even download and install the latest version from the manufacturer's website.

3. Confirm smart card driver

Some smart cards may require specific drivers or software to be recognized. Please confirm and install the relevant drivers.

4. Verify that the smart card is activated

Sometimes the system will set the smart card to "disabled" status. Find the smart card reader in "Device Administrator", right-click and select "Enable Device". and change the startup type to ‘automatic’

5. Verify that the smart card is functioning properly

You can insert the smart card into another card reader that works normally, or insert another smart card into the current card reader to confirm whether the problem is with the smart card itself.

6. Use Windows Smart Card Service

Confirm that the Windows Smart Card Service is started. pressWin + R,enterservices.msc, find the "Smart Card" service (the name may be Smart Card Device Enumeration Service) and set it to "Automatically" start.
If the service is not started, you can start it manually.

7. Check for operating system updates

Some smart cards or card readers may require the latest operating system updates. Check for and install available Windows updates to ensure system and device compatibility.

The above method should help solve the problem where the smart card reader is displayed in the device administrator but the smart card cannot be seen.

Linux

Linux version comparison

1. Ubuntu

Ubuntu is a Debian-based Linux distribution suitable for beginners. It has large community support and friendly user interface. Suitable for personal desktop use, server or development purposes.

Advantages: Easy installation, rich community resources, LTS provides long-term support
Disadvantages: Heavy in some cases, may be slow on older hardware

2. CentOS Stream

CentOS Stream is a rolling update version of Red Hat Enterprise Linux (RHEL) suitable for server and enterprise environments.

Advantages: high stability, strong compatibility with RHEL
Disadvantages: slow update speed, suitable for conservative environments, not suitable for cutting-edge applications

3. Fedora

Fedora is a Linux distribution sponsored by Red Hat that has the latest features and technologies for developers and technology enthusiasts.

Advantages: Has the latest technology and updates quickly
Disadvantages: Frequent updates, may be unstable

4. Debian

Debian is a veteran Linux distribution known for its stability and open source ethos, suitable for both server and desktop use.

Advantages: extremely stable, rich software packages
Disadvantages: Slow version updates, software may not be the latest

5. Arch Linux

Arch Linux 是一个滚动更新的发行版，面向高阶用户。 Its KISS principle (Keep It Simple, Stupid) gives users complete control over the system.

Pros: Highly customizable, always up to date
Disadvantages: Not suitable for beginners, the configuration process is cumbersome

6. openSUSE

openSUSE is available in two versions: Leap and Tumbleweed. Leap is a stable version and Tumbleweed is a rolling update version.

Advantages: Powerful management tools (such as YaST), suitable for various purposes
Disadvantages: The community size is relatively small

7. Manjaro

Manjaro is a Linux distribution based on Arch, but optimized for beginners, providing a simpler installation and usage experience.

Advantages: Based on Arch and easier to use
Disadvantages: Relatively independent from the Arch community, updates may be delayed

Install Linux

1. Preparation

Before installing Linux, you need to complete the following preparations:

Choose a suitable Linux distribution (such as Ubuntu, Debian, Fedora, etc.).
Download the ISO file of the selected distribution.
Prepare a USB flash drive with at least 8GB capacity and download a burning tool (such as Rufus or Etcher).

2. Create a bootable USB flash drive

Use the following steps to burn the ISO file to a USB flash drive:

Install a burning tool (such as Rufus).
Insert the USB flash drive and start the burning tool.
Select the Linux ISO file and set the target device as a USB flash drive.
Start burning, and after completion, you will get a bootable USB flash drive.

3. Start the installer

Follow these steps to start the Linux installer:

Restart your computer and enter BIOS/UEFI Setup (usually F2, F12, DEL, or ESC).
Set the boot sequence to boot from USB.
Insert the prepared USB flash drive and save the settings before restarting.

4. Install Linux

During the installation process you need to complete the following steps:

Select language, time zone and keyboard configuration.
Select the installation type (such as clean disk installation, dual-system installation or custom partition).
Set username, password and hostname.
After completing the setup, the system will begin the installation, which may take a few minutes to an hour.

5. Complete the installation and reboot

Once the installation is complete, follow these steps for final setup:

Remove the USB flash drive and restart the computer.
Enter the newly installed Linux system and complete the first login.
Perform software updates and necessary driver installations to ensure normal system operation.

6. Recommended actions after installation is complete

After the new system is installed, you can consider the following operations to optimize the user experience:

Install commonly used software and tools (such as browsers, text editors, development environments).
Learn basic Linux commands to get started.
Set up a backup plan to prevent data loss.

Check current Linux version

View release version (most commonly used)

cat /etc/os-release

For example:

NAME="Ubuntu"
VERSION="22.04.3 LTS"
ID=ubuntu
PRETTY_NAME="Ubuntu 22.04.3 LTS"

---

Just look at the pretty output (recommended)

lsb_release -a

Output example:

Distributor ID: Ubuntu
Description:    Ubuntu 22.04.3 LTS
Release:        22.04
Codename:       jammy

---

Check the Linux kernel version (Kernel)

uname -r

Output:

5.15.0-97-generic

---

View complete system information

uname -a

It will include core version, architecture, compilation time and other information.

---

View CPU/Architecture

uname -m

For example:

x86_64

---

Check Debian / Ubuntu version (another way)

cat /etc/issue

---

Check CentOS / RHEL / AlmaLinux / RockyLinux version

cat /etc/redhat-release

---

FAQ

lsb_releaseNot found → Install:sudo apt install lsb-release
The file path is different for different distributions, but/etc/os-releasealmost universal

Linux backup

Use tar to create a full system backup

Can be usedtarThe command packs the entire system into a compressed archive. It is recommended to execute it in single-player mode or enter rescue mode to ensure that the files will not change during the backup process.

sudo tar --exclude=/proc --exclude=/tmp --exclude=/mnt --exclude=/dev --exclude=/sys \
--exclude=/run --exclude=/media --exclude=/lost+found -cvpzf /mnt/backup/system-backup.tar.gz /

illustrate:

--exclude: Exclude directories that do not need to be backed up.
/mnt/backup/: It is recommended to back up to a mounted external disk or network device.

Using rsync for image backup

rsyncCan be used to make system images and keep directories synchronized.

sudo rsync -aAXv --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found"} / /mnt/backup

illustrate:

-aAX: Preserve permissions, symbolic links, special files, and mount point structures.
Suitable for system migration or quick restore.

Using Clonezilla

ClonezillaIt is an open source disk image backup tool that can back up the entire disk or specific partitions.

Download the Clonezilla ISO and create a bootable USB.
Reboot from USB.
choosedevice-imageMode backup to external device or network.
Follow the instructions to select the source partition and storage destination.

Using Timeshift (for desktop systems)

TimeshiftSuitable for desktop users, supports snapshot and restore functions.

Install:sudo apt install timeshift（Debian/Ubuntu）
implement:sudo timeshift-gtkorsudo timeshift --create
Select backup method (RSYNC or BTRFS), snapshot frequency and storage location.

Recommended actions after backup

Regular backup: It is recommended to create a schedule for automatic backup.
Verify backup: usetar -tvforrsync --dry-runVerify content.
Offline storage: Store backup files on an external hard drive or cloud to prevent system damage.

Linux mounts Windows network shared folder

Install necessary packages

Install firstcifs-utils, which is the tool needed to mount a Windows shared directory:

sudo apt update
sudo apt install cifs-utils

Create a mounting directory

Select or create a mount point, for example:

sudo mkdir -p /mnt/windows_share

Mount shared folder

Use the following command to mount:

sudo mount -t cifs //192.168.1.100/share_name /mnt/windows_share \
-o username=your_username,password=your_password,domain=YOUR_DOMAIN,iocharset=utf8,file_mode=0777,dir_mode=0777

illustrate:

//192.168.1.100/share_name: Windows host IP and share name.
/mnt/windows_share:Mount point.
username/password: Windows account password.
domain: Can be omitted if there is no domain.
file_mode/dir_mode: Set file and folder permissions.

Add the mount settings to fstab for automatic mounting at boot

It is recommended to write the password into the certificate file to improve security:

sudo nano /etc/samba/creds

The content is as follows:

username=your_username
password=your_password
domain=YOUR_DOMAIN

Modify permissions:

sudo chmod 600 /etc/samba/creds

edit/etc/fstab：

sudo nano /etc/fstab

join in:

//192.168.1.100/share_name /mnt/windows_share cifs credentials=/etc/samba/creds,iocharset=utf8,file_mode=0777,dir_mode=0777 0 0

Test mount

sudo mount -a

If there is no error message, the mount is successful.

APT suite management tool

Basic concepts

APT (Advanced Package Tool) is a commonly used package management tool for Debian and its derivative systems (such as Ubuntu, ChromeOS Linux containers). It is used to automate the installation, upgrade, removal of software, and solve package dependency issues.

Common commands

Update kit list：
```
sudo apt update
```
Upgrade all packages：
```
sudo apt upgrade -y
```
Install specified packages：
```
sudo apt install -y package name
```
Remove specified package：
```
sudo apt remove package name
```
Remove a package and its configuration files：
```
sudo apt purge package name
```
Clean out unnecessary packages：
```
sudo apt autoremove -y
```
search package：
```
apt search keyword
```
View package information：
```
apt show package name
```

Differences between APT and dpkg

dpkg: Low-level tool, only responsible for installing or removing a single.debfiles, dependencies will not be automatically processed.
apt: A high-end tool that automatically downloads packages and resolves dependency issues, making it more suitable for daily use.

Practical suggestions

Perform oftensudo apt update && sudo apt upgradeto keep the system up to date.
Use before installing new packagesapt searchorapt showConfirm version and description.
If you encounter dependency errors, try:
```
sudo apt -f install
```

iconv encoding conversion tool

Introduction

iconvIt is a tool used for text file encoding conversion, commonly used to convert Big5, GB2312, UTF-8, UTF-16, etc. to each other.

basic grammar

iconv -f original encoding -t target encoding input.txt -o output.txt

-f: Source encoding (from)
-t: Target encoding (to)
-o: Output file (can be omitted, output to stdout by default)

Common encoding names

UTF-8
BIG5(Traditional Chinese)
GB2312 / GBK(Simplified Chinese)
ISO-8859-1
UTF-16 / UTF-16LE / UTF-16BE

example

1. Convert Big5 to UTF-8

iconv -f BIG5 -t UTF-8 input.txt -o output.txt

2. Convert UTF-8 to Big5 (direct override)

iconv -f UTF-8 -t BIG5 input.txt > tmp.txt && mv tmp.txt input.txt

3. File embedded pipeline conversion

cat input.txt | iconv -f UTF-8 -t BIG5 | less

Detect file encoding

iconv itself does not have automatic detection function, it can be used withfileoruchardetuse:

file -i input.txt
uchardet input.txt

Handle failed transcoding (ignore errors)

iconv -f BIG5 -t UTF-8 -c input.txt -o output.txt

-cIndicates that characters that cannot be converted are ignored

Things to note

Please make sure the original encoding is correct first, otherwise the conversion result may be garbled.
Binary files such as .doc/.xls are not supported
UTF-16 etc. may have BOM (Bit Order Mark), please pay attention to whether it needs to be removed after conversion.

Ubuntu UI

GNOME desktop environment

Ubuntu uses GNOME as its desktop environment by default. This is an intuitive and modern graphical interface, and the design concept emphasizes simplicity and focus. The interface mainly consists of the top status bar, the left activity bar, and the full-screen application launcher.

Event Navigation and Sidebar (The Dock)

The vertical bar on the left side of the screen, called the Dock, holds frequently used application icons. As the application executes, a marker will appear below the icon. Users can adjust the order by dragging, or right-click to pin apps to the Dock. Click the nine-dot icon at the bottom of the Dock to open the list of all programs.

Top Bar

The bar at the top of the screen contains the following functions:

Activities: Located in the upper left corner, click to view all open window thumbnails and virtual desktop switchers.
Clock and Calendar: Located in the center, click to view the date, notification center and world clock.
System menu: Located in the upper right corner, including network connection, volume, power management, brightness adjustment and quick setting menu.

Window management and workspace

Ubuntu supports multiple workspaces, allowing users to place different types of tasks on different virtual desktops. You can quickly switch windows by pressing the Super key (usually the Windows key on your keyboard). The windows have an automatic snapping function. Drag the window to the edge of the screen to automatically fill half of the screen, making it easier to process tasks side by side.

Archivist (Nautilus)

The default file manager provides a simple navigation experience. The left sidebar displays commonly used folders (such as files, pictures, downloads) and integrates cloud storage spaces such as Google Drive. It supports paginated browsing function, allowing users to manage multiple paths in a single window.

Appearance customization

Users can freely switch between light mode and dark mode through the appearance options in system settings. In addition, Ubuntu allows you to adjust the theme accent color (Accent Color), and customize the position of the Dock (bottom, left or right) and whether to automatically hide it, providing a high degree of personalization flexibility.

GNOME desktop environment

Core features

GNOME is one of the most popular desktop environments among Linux distributions (default choice for Debian, Ubuntu, Fedora). It emphasizes simplicity, focus and modern user experience, and its design logic is significantly different from the traditional Windows window layout.

Activities Overview:Press the Super key (Windows key) to open and view all open windows, virtual desktops, and application searches.
Extensions:Through GNOME Extensions, users can customize the interface, such as adding a taskbar (Dash to Panel) or application menu.
Software integration:It has a complete toolbox of native applications, such as Nautilus (file), Gedit (text editing), Terminal, etc.

Main components and tools

Component name	Function description
GTK	Graphical toolkit for building GNOME interfaces.
Mutter	Window manager and Wayland compositor.
GNOME Shell	The core of the graphical interface for direct user interaction (top bar, search function, etc.).
Gnome Tweaks	Essential tool for adjusting fonts, themes and advanced settings.

Commonly used shortcut keys

Super:Open event overview and search.
Super + A:Show application list.
Super + PgUp / PgDn:Switch between different virtual desktops (Workspaces).
Super + Arrow keys:Snap windows (align the left and right sides of the screen).
Alt + F2:Open the command execution window (enterrGNOME Shell can be restarted, X11 only).

Custom suggestions

If you are accustomed to using Windows, it is recommended to install the following extensions to optimize GNOME:

1. Dash to Dock: Convert the sidebar to a Dock fixed at the bottom.
2. AppIndicator Support: Display the icon of the background program in the top column.
3. Arc Menu: Provides traditional start menu.

Version confirmation command

To confirm the currently installed GNOME version in the terminal, you can use the following command:

gnome-shell --version

GNOME desktop shortcut creation

Using the desktop entry point file (.desktop)

In Debian or other Linux distributions using GNOME/KDE, desktop shortcuts are created via.desktopdefined by the file. This file is usually generated in the system directory after VS Code is installed, you just need to copy it to the desktop.

1. Copy existing profile

Open a terminal and execute the following command to copy the system's VS Code shortcut to your desktop folder:

cp /usr/share/applications/code.desktop ~/Desktop/

2. Grant execution permissions

After copying, you need to give the file execute permissions, otherwise it may be treated as a plain text file:

chmod +x ~/Desktop/code.desktop

3. Allow startup (for GNOME users)

If you are using the GNOME desktop environment, the icon may appear as a gear or have a warning sign after copying. Please click on the icon on your desktopRight click, then select"Allow Launching". The icon will then change to the correct VS Code logo.

Manually create shortcut files

If the file cannot be found in the above path, you can create one manually. Enter in the terminal:

nano ~/Desktop/vscode.desktop

Then paste the following:

[Desktop Entry]
Name=Visual Studio Code
Comment=Code Editing. Refined.
GenericName=Text Editor
Exec=/usr/bin/code --unity-launch %F
Icon=vscode
Type=Application
StartupNotify=true
StartupWMClass=Code
Categories=Utility;TextEditor;Development;IDE;
MimeType=text/plain;inode/directory;application/x-code-workspace;

Save and exit (Ctrl+O, Enter, Ctrl+X), then do the samechmod +xinstruction.

Create a symbolic link (Symbolic Link)

Another quick method is to create a soft link. Although the icon display effect on some desktops is not as complete as the .desktop file, the operation is the easiest:

ln -s /usr/bin/code ~/Desktop/VSCode

Method comparison table

method	advantage	shortcoming
Copy .desktop file	Display the complete icon and right-click menu function.	You need to click "Allow startup" additionally.
Create files manually	Startup parameters (such as working directory) can be customized.	The content is complicated and prone to typos.
Symbolic link (ln -s)	The instructions are the simplest.	The icon may just be a normal executable file icon.

Ubuntu screen lock and logout

Adjust screen auto-off time

By default, Ubuntu turns off the screen and enters a locked state after a period of inactivity, which is often mistaken for automatic logout. To adjust or turn off this feature, follow these steps:

turn onSettingsprogram.
Click on the menu on the leftPower。
In the Power Saving section, clickScreen Blank。
Select from the drop-down menuNever。

Turn off automatic screen lock

You can set the system not to automatically lock even when the screen is off, so you don't need to enter your password when you turn the screen back on:

Click on the menu on the left side of the settings windowPrivacy, then clickScreenOr search directlyScreen Lock。
WillAutomatic Screen Lockswitch to off.
At the same time,Lock Screen DelaySet to the maximum value, or disable it directly with the above switch.

Adjust auto-pause settings

If your system automatically enters sleep or pause mode, it will also require you to log in again:

return toPowerSettings page.
ClickAutomatic Suspend。
Turn the switch to off, or set it to "on battery" and "plugged in" respectively.Never。

Prevent remote connections from automatically disconnecting

If you find that your remote connection via SSH is automatically disconnected, this is usually due to a timeout setting on the server. You can modify your connection settings to keep them working:

Modify the SSH configuration file on the client computer:sudo nano /etc/ssh/ssh_config。
join inServerAliveInterval 60, which causes the client to send a signal to the server every 60 seconds to maintain the connection.

Ubuntu uses Chinese input method

Install Chinese input method framework

Ubuntu usually defaults to usingIBusorFcitxAs an input method framework, here we use the commonFcitx5For example:

sudo apt update
sudo apt install fcitx5 fcitx5-config-qt fcitx5-chinese-addons

Set input method environment variables

Open the environment profile (depending on the shell used, it may be~/.xprofile、~/.profileor~/.bashrc）：

nano ~/.xprofile

Add the following:

export GTK_IM_MODULE=fcitx5
export QT_IM_MODULE=fcitx5
export XMODIFIERS="@im=fcitx5"

Restart the system or log out

For the settings to take effect, it is recommended to restart or log out and then log in again.

Turn on Fcitx5 settings

Clickapplication menu→ SearchFcitx5 Configuration, after turning it on, press+Added input method.

Search and add one of the following input methods:

Pinyin（Pinyin）
Cangjie（Cangjie）
quick fix（Quick）
Wubi（Wubi）

Switch input method

The default switching shortcut key isCtrl + Space, can be modified in Fcitx5 settings.

Other alternatives

If you prefer other input method frameworks, you may also consider:

Ibus + Chewing(natural phonetic notation):sudo apt install ibus-chewing
Rime Zhongzhouyun input method：sudo apt install fcitx5-rime

Install and use the row and column input method in Ubuntu

What is row-row input method?

The row-column input method is a root-based Chinese input method widely used in Taiwan. It supports fast input of Traditional Chinese and is suitable for users who are familiar with keyboard layout.

Use Fcitx5 to install the row and column input method

Install the Fcitx5 framework and Chinese extension kit:

sudo apt update
sudo apt install fcitx5 fcitx5-config-qt fcitx5-chinese-addons

Set input method environment variables:

nano ~/.xprofile

Add the following:

export GTK_IM_MODULE=fcitx5
export QT_IM_MODULE=fcitx5
export XMODIFIERS="@im=fcitx5"

Log out and back in, or restart the system.
turn onFcitx5 settings(Fcitx5 Configuration), press+Add input method.
searchranksorArray, then select Join.

Use row and column input method

Switch input method: Use by defaultCtrl + SpaceorSuper + Space。
Start typing the root characters to enter Traditional Chinese.

Other input method framework options

If you are using IBus, consider installing Rime to support queues:

sudo apt install ibus-rime

After starting IBus and setting up Rime, you can also enable the "Range" scheme in it.

Rime input method enables column scheme

Edit profile:~/.config/fcitx5/rime/default.custom.yamloribusrime under the path.
Add the following to enable:

patch:
  schema_list:
    - schema: array30

Redeploy input method: pressCtrl + `Call the Rime menu and select Redeploy.

Check input method framework

Method 1: Use environment variable checking

Open the terminal and enter the following command:

echo $XMODIFIERS
echo $GTK_IM_MODULE
echo $QT_IM_MODULE

Output result example:

@im=ibusIndicates that IBus is being used
@im=fcitxorfcitx5Indicates that Fcitx/Fcitx5 is used

Method 2: Check the starting input method program

Enter the following command to view the currently executed input method related programs:

ps aux | grep -E 'ibus|fcitx'

Example results:

Appearibus-daemonIndicates that IBus is being used
Appearfcitxorfcitx5Indicates that Fcitx/Fcitx5 is used

Method Three: Graphical Interface Check

Check the input method setting method in "Settings":

Open "Settings" → "Region & Language"
Check if the input source shows IBus or Fcitx

Method 4: Use the im-config tool

Install and executeim-configtool:

sudo apt install im-config
im-config -m

The currently used input method framework will be displayed, for example:

default missing
IBus is selected

Switch input method framework

To switch, execute:

im-config

Select the input method framework to be used in the graphical interface (such as Fcitx, IBus, None, etc.), select and log in again.

Ubuntu desktop executable shortcut

Overview

To create a shortcut ($\text{Launcher}$) on the Ubuntu desktop that executes a specific $\text{.sh}$ script when clicked, you need to create a $\text{.desktop}$ file. This file is a standard desktop project configuration file specified by $\text{freedesktop.org}$.

The following assumes that your script $\text{b.sh}$ is located in your "home directory" ($\text{Home Directory}$) and you want to execute the script in the terminal.

---

Step 1: Make sure the script is executable

First, you must ensure that the $\text{b.sh}$ file itself has execute permissions.


chmod +x ~/b.sh

(Note: $\text{\~}$ represents your home directory, such as $\text{/home/username/}$)

Step 2: Create a .desktop shortcut file

You can use any text editor (such as $\text{gedit}$ or $\text{nano}$) to create a new file on your desktop and name it $\text{b.sh.desktop}$ (the name can be customized, but must end with $\text{.desktop}$).


nano ~/Desktop/b.sh.desktop

Copy and paste the following into the file:

[Desktop Entry]
Version=1.0
Type=Application
Terminal=true
Name=Execute b.sh script
Comment=Click on the b.sh file in the executor home directory
Exec=/bin/bash -c "cd ~ && ./b.sh"
Icon=utilities-terminal
Categories=Application;Utility;

---

Step 3: Description of each parameter

parameter	illustrate
Type=Application	Defines this file as an application launcher.
Terminal=true	Must be set to $\text{true}$. This will tell the system to open a terminal window to run the script when the command is executed so that you can see the output of the script.
Name	The name that appears below the desktop shortcut icon.
Exec	Define the instructions to be executed. Here, we use $\text{/bin/bash -c "cd \~ \&\& ./b.sh"}$ to ensure that the script is executed correctly in your home directory.
Icon	Set an icon for the shortcut. You can specify the name of the system's built-in icon (such as $\text{utilities-terminal}$), or specify the full path to an icon file (such as $\text{/path/to/my/icon.png}$).

---

Step 4: Authorize and trust the launcher

In most modern Ubuntu or $\text{Gnome}$ environments, when you place a $\text{.desktop}$ file on the desktop, the system may initially treat it as just a text file for security reasons.

**Right-click**: Right-click on the $\text{b.sh.desktop}$ file you created.
**Select Properties**: Enter the file properties window.
**Permissions Tag**: Check the option "Allow executing file as program" ($\text{Allow executing file as program}$).
**Trust Launcher**: Double-click the $\text{b.sh.desktop}$ file. The system may pop up a dialog box asking you if you want to "Trust and Launch" ($\text{Trust and Launch}$) this file. Click OK.

After completing the above steps, the icon on the desktop should display correctly, and double-clicking it will open a terminal window and execute your $\text{b.sh}$ script.

Service restart verification

Problem description

When you try to run on Ubuntu or other Linux systems using systemd, usesystemctl restart [email protected]When you run the command to restart the Chrome Remote Desktop service, you will be prompted for authentication (that is, asking for a password). This is because the restart operation of the service is considered a system-level operation that requires elevated privileges.

Solution: Use Polkit to set up password-free operation

To allow your users to restart this specific service without requiring a password, you can create a local authorization rule through Polkit (PolicyKit). Polkit is responsible for controlling how unprivileged programs communicate with privileged programs, and is the standard way of handling such permission prompts.

Step 1: Create a Polkit rules file

exist/etc/polkit-1/localauthority/50-local.d/Create a new rules file in the directory. we use99-chrome-remote-desktop-restart.pklaAs a file name (the file name can be customized, but it is recommended to use.pklaend):

sudo nano /etc/polkit-1/localauthority/50-local.d/99-chrome-remote-desktop-restart.pkla

Step 2: Add new rule content

In this file, paste the following content. This rule allows foradmingroup (orsudogroup (the exact group name depends on your Ubuntu version and configuration) to restart the service without requiring a password:

[Allow user to restart chrome-remote-desktop service]
Identity=unix-group:sudo
Action=org.freedesktop.systemd1.manage-units
ResultAny=yes
ResultInactive=yes
ResultActive=yes

Identity: Specify the user or group to which this rule applies. In Ubuntu, users with administrative rights usually belong tosudooradmingroup. Please select the correct group based on your system conditions.
Action: Lists systemd Polkit actions related to service management.
ResultActive/Inactive/Any: Set whether authorization is required in different session states (active, inactive or any state). set toyesIndicates that the operation is allowed without a password.

Step 3: Save and exit

store.pklaarchive and exit the editor.

Step 4: Reload Polkit or reboot the system

In order for Polkit to load the new rules immediately, you may need to restart the Polkit service, or more reliably, restart the system:

sudo systemctl restart polkit.service

Or, if a simple service restart doesn't work, restart the entire system.

Step 5: Verify password-free execution

Now you can try executing the reboot command again and the password should no longer be asked:

systemctl restart [email protected]

Please note that the above settings are user (or group) and service specific. This will not affect other operations that require administrator privileges.

Set boot delay execution script

Method overview

In Ubuntu systems, there are many ways to set a delay of a few seconds to execute scripts after booting. The most modern, reliable, and recommended method is to use systemd's Service Unit because it can precisely control execution timing and latency.

Recommended method: Use Systemd service unit

This method involves creating a systemd service file that specifies to wait a specific number of seconds after system startup is complete (or a certain goal is reached) before executing your script.

Step 1: Confirm script path and permissions

Assume your scriptb.shstored in/usr/local/bin/, and executable permissions have been set:

sudo chmod +x /usr/local/bin/b.sh

Step 2: Create Systemd service profile

exist/etc/systemd/system/Create a new service file in the directory, for examplerun-bsh.service：

sudo nano /etc/systemd/system/run-bsh.service

Step 3: Set up service content

Paste the following into your service profile. we useExecStartPreto implement the delay function.

[Unit]
Description=Delayed execution of b.sh script
After=network.target multi-user.target

[Service]
Type=oneshot
# Set the delay seconds, here set the execution delay of 15 seconds after booting
ExecStartPre=/bin/sleep 15
#Specify the script path to be executed
ExecStart=/usr/local/bin/b.sh

[Install]
WantedBy=multi-user.target

After=network.target multi-user.target: Ensure that the service starts after the network service is started and the multi-user environment is ready.
ExecStartPre=/bin/sleep 15: This is the key to achieving latency. It will execute the main command (ExecStart), let systemd pause for 15 seconds. You can use15Replace with your desired delay in seconds.
Type=oneshot: Indicates that this service is a single-execution script and will end after execution.

Step 4: Enable and start the service

After saving the file, you need to tell systemd to reload the configuration and enable the new service so that it runs automatically on every boot:

sudo systemctl daemon-reload
sudo systemctl enable run-bsh.service

Now, after restarting the system,b.shIt will be executed with a delay of 15 seconds after power on.

Alternate method: crontab's @reboot combined with sleep

If you prefer to usecronscheduler, which can also be combined with@rebootoptions andsleepCommand to achieve:

Open the user's crontab editor:
```
crontab -e
```
Add the following line at the end of the file, for example, delay execution for 20 seconds:
```
@reboot /bin/sleep 20 && /usr/local/bin/b.sh &
```

This method will be executed when the system starts, and then delays execution for 20 seconds before executing the script. Pay attention to the ending&Symbol, indicating to let the script execute in the background to avoid blocking cron tasks.

VirtualBox installation Ubuntu default password

Default password source

If you installed Ubuntu in VirtualBox usingUnattended Installationfunction, VirtualBox will automatically create a file namedvboxuserof users.

In most cases, the default password is:

changeme

Why does this account appear?

This is the default setting of VirtualBox designed to simplify the installation process. When you click "New" virtual machine, if you have not changed the account information in the "Auto-Install" tab, the system will apply the default values:

username: vboxuser
password: changeme
Hostname: ubuntu(or the name you set)

What if the default password is invalid?

If you trychangemeBut unable to log in, please check the following points:

Keyboard layout:Make sure your keyboard layout is correct (e.g. Caps Lock is on).
Custom settings:Recall whether you manually entered other passwords in the "Guest OS Unattended Install" menu during the process of creating a new virtual machine in VirtualBox.

How to change password

After successfully logging in, for security reasons, it is recommended that you change your password immediately. You can open Terminal and enter:

passwd

You will be asked to enter your old password (changeme) and then set your new password.

How to avoid automatically creating users

If you wish to set your own username and password during the installation process, please check the box when creating the virtual machine.Skip Unattended Installation(Skip automatic installation) option. The system will then guide you to the traditional Ubuntu installation screen, allowing you to manually enter customized account information.

The default mechanism for the root account in Ubuntu

In Ubuntu systems (including versions installed through VirtualBox),The root account has no password by default, and is locked.

This does not mean that the password is "blank", but that the system does not allow direct login as root. Ubuntu is designed throughsudocommand to allow general users with administrator rights (such as yourvboxuser) to perform tasks that require high privileges.

How to execute commands that require root privileges

When you need to execute a system management command, please addsudo. What you will be asked to enter isPassword for your current account (vboxuser), that ischangeme。

sudo apt update

If you really need to switch to root identity

If you wish to switch to a terminal environment with root privileges, use the following command:

sudo -i

Likewise, the system will ask forvboxuserpassword (changeme), your prompt character will becomeroot@ubuntu:~#。

How to set a password for root (not recommended)

Although this is not recommended for security reasons, if you do need to set a unique password for root, you can use the following command:

sudo passwd root

Enter your current password (changeme)。
Enter the new password you want for root (you need to enter it twice to confirm).

Summarize

root default password:None (account locked).
Management operations:usesudoand entervboxuserpasswordchangeme。

Ubuntu terminal cannot be opened

Common cause analysis

In Ubuntu under VirtualBox environment, the terminal cannot be opened (no response after clicking the icon or the window crashes), which is usually related to the following reasons:

Language setting conflict:The most common reasons. When the system language is set to Traditional Chinese but the Locale setting is incomplete, GNOME Terminal will fail to start.
Python version issues:The terminal relies on Python to operate. If the system default Python link is manually changed, it may become invalid.
Display driver compatibility:VirtualBox's 3D acceleration feature sometimes interferes with X11 window rendering.

Solution 1: Use TTY interface to fix the language (most effective)

Since you cannot open a terminal window now, we need to enter "text-only mode" to execute the repair instructions.

In the virtual machine window, clickCtrl + Alt + F3(or F4~F6). This will switch to the TTY3 text login screen.
Enter usernamevboxuserand press Enter. Or log in directly as root.
Enter passwordchangeme(Characters will not be displayed while typing) and press Enter.
After successfully logging in, enter the following command to reset the language:
```
sudo localectl set-locale LANG=en_US.UTF-8
```
After execution, pressCtrl + Alt + F1(or F2) returns to the graphical interface.
Restart the computer or log out and then log in again, and try to open the terminal.

Solution two: Disable 3D acceleration

If the window environment is unstable and the program cannot be started, try turning off hardware acceleration.

First, the virtual machineShut down。
Return to the main interface of VirtualBox and click on your Ubuntu machine $\rightarrow$Settings。
ClickDisplay。
UncheckEnable 3D Acceleration。
Restart the virtual machine.

Solution three: Install an alternative terminal (xterm)

If GNOME Terminal is damaged, you can first install a basic terminal tool to troubleshoot the problem.

Also enterCtrl + Alt + F3text interface and log in.

Execute the installation instructions:

sudo apt update && sudo apt install xterm

Return to the graphical interface and search in the applicationxtermand turn it on. If xterm can be opened, it means that the original gnome-terminal configuration file is damaged.

Packing and decompression using tar command

what is tar

tar is a commonly used tool in Linux and Unix systems for packaging and decompressing archives. The original meaning of tar is "tape archive", which can integrate multiple files and folders into one file (usually a .tar file) for easy transfer or backup.

basic grammar

The basic instruction format of tar is as follows:

tar [options] file name

Common options include:

-c:Create a new tar package.
-x: Decompress the tarball.
-v: Show detailed process.
-f:Specify the file name.
-z: Compress or decompress gzip format archives.
-j: Compress or decompress bzip2 format files.

Example: Create tar package

Suppose there is a file calledmy_folderfolder that you want to package intoarchive.tar：

tar -cvf archive.tar my_folder

After execution, a file namedarchive.tarThe tar package containsmy_foldercontent.

Example: Decompressing a tarball

To unziparchive.tar, use the following command:

tar -xvf archive.tar

After decompression,my_folderThe contents will be restored to the current directory.

Example: Creating a gzip-compressed tarball

To simultaneously package and compress an archive into a gzip-formatted archive (.tar.gz), use-zOptions:

tar -czvf archive.tar.gz my_folder

This command will generatearchive.tar.gz, including compressedmy_folder。

Example: Decompressing a gzip-formatted tar file

To unziparchive.tar.gz, use the following command:

tar -xzvf archive.tar.gz

This command will decompress the file and restoremy_foldercontent.

More advanced operations

List tar package contents:
```
tar -tvf archive.tar
```
Add the specified archive to an existing tarball:
```
tar -rvf archive.tar new_file
```
Extract only a certain file:
```
tar -xvf archive.tar path/to/file
```

in conclusion

tar is a powerful tool that can package and compress archives, suitable for backup and archive transfer. Familiarity with the basic syntax and common options can help you manage files more efficiently on your Linux system.

File batch rename

Example: Batch rename files

Assume our file name is in the following format:

file1,data1.txt
file2,data2.txt
file3,data3.txt

We want to extract the first part of each line as the new file name.

Step 1: Prepare files

First, make sure you have an archive (e.g.filenames.txt), which contains the name of the file that needs to be renamed:

file1,data1.txt
file2,data2.txt
file3,data3.txt

Step 2: Create a Bash script

The following is an example Bash script for batch renaming:

#!/bin/bash

# Read each line in the file
while IFS=, read -r new_name old_name; do
    # Check if the old file exists
    if [ -f "$old_name" ]; then
        # Use the mv command to rename the file
        mv "$old_name" "$new_name.txt"
        echo "'$old_name' has been renamed to '$new_name.txt'"
    else
        echo "File '$old_name' does not exist."
    fi
done < filenames.txt

Step 3: Execute the script

Save the above script asrename_files.sh。
Grant execution permissions:
```
chmod +x rename_files.sh
```
Execute the script:
```
./rename_files.sh
```

illustrate

while IFS=, read -r new_name old_name; do: This line of code readsfilenames.txtfor each line in , with commas as delimiters, assign the first part tonew_name, the second part is assigned toold_name。
[ -f "$old_name" ]: Check if the old archive exists.
mv "$old_name" "$new_name.txt": Rename the old file to the new file name, appending.txtextension.

Method 2 - using cut

Use cut to read the files in the directory and write them into a.sh

$ for i in */*; do j=`echo $i|cut -d '/' -f 1`;k=`echo $i|cut -d ' ' -f 2`;echo mv '"'$i'"' $j'/'$j'_'$k; done > a.sh

output a.sh

mv "16/track 02.mp3" 16/16_02.mp3
mv "16/track 03.mp3" 16/16_03.mp3
mv "16/track 04.mp3" 16/16_04.mp3
...

Then execute a.sh

How to use the bc instruction

What is BC?

bc is a "basic calculator" (Basic Calculator), which is the abbreviation of Linux and Unix The system's command line tool for mathematical operations. It supports high-precision arithmetic operations and can handle floating point numbers, variables and conditional operations. It is a powerful tool for performing fast calculations.

How to start bc

To start bc, type directly in the terminal:

bc

After starting, you can enter expressions in the command line, for example:

3 + 5

pressEnterAfter that, you can get the result.

Basic usage of bc

Addition, subtraction, multiplication and division:use+、-、*、/Perform basic arithmetic operations. For example:
```
10 * 5
```
Modulo operation:use%Calculate the remainder. For example:
```
10 % 3
```
brackets:Use parentheses to control operation precedence. For example:
```
(3 + 5) * 2
```

Handle floating point numbers

bc does not support floating point operations by default and needs to be setscaleSpecify the number of decimal places. For example:

scale=2
5 / 3

The result is1.66。

Use variables

bc supports variable assignment and operations. For example:

a=10
b=20
a + b

The result is30。

Calculate decimal exponent

bc does not directly support decimal exponentiation, but can use natural logarithms (l()) and the exponential function (e()) to achieve. For example, calculate2^3.5：

scale=5
e(3.5*l(2))

The steps here are as follows:

usel(2)Calculate the natural logarithm of 2.
Multiply the natural logarithm by the exponential value (3.5).
usee()Calculate the exponential value of the natural logarithm and get the result.

The execution result will be a high-precision decimal.

Advanced operations

Conditional judgment:Conditional operators can be used. For example:
```
if (3 > 2) print "Yes"\n
```
Function usage:For example, calculate the square root:
```
sqrt(16)
```
Automatically exit:use-qOption to start bc, you can hide the startup prompt message:
```
bc -q
```

Example: Single row operation

Single-line operations can be performed directly in the terminal. For example:

echo "scale=5; e(3.5*l(2))" | bc -l

The result is the result of the exponential operation in decimal format.

in conclusion

bc is a powerful and flexible tool that can not only perform basic arithmetic operations, but also handle advanced conditional and function calculations, including complex operations such as decimal exponents. Familiarity with the bc command can help you quickly complete various computing tasks in Linux systems.

bc command update

Since performance bottlenecks in GNU bc have existed for many years, many modern systems have moved to using GNU bc developed by Gavin Howardgh-bc. If you find that your Chromebook or computer is running too slowly, you can update or replace it as follows.

1. Chromebook (ChromeOS / Crostini)

Chromebooks' Linux container defaults are based on Debian, which typically installs an older version of GNU bc. You can try to obtain a high-performance version through source code compilation:

Step 1: Install compilation tools
sudo apt update && sudo apt install build-essential
Step 2: Download the high-performance version bc
Go to GitHub and searchgavinhoward/bc, or download using git.git clone https://github.com/gavinhoward/bc.git
Step 3: Compile and install
./configure -O3(Turn on advanced optimization options)
make && sudo make install

2. Cygwin (Windows)

bc in the Cygwin package repository is updated slowly. To improve performance, it is recommended to directly switch to the Windows native high-performance version to avoid Cygwin's simulation loss:

Using BusyBox for Windows: BusyBox's built-in bc is generally lighter and faster than the Cygwin version.
Custom compilation: Using MinGW or MSVC to compile gh-bc on Windows, this output.exeThe execution efficiency will be much higher than the Cygwin version.

3. Comparison table of versions of each platform

version name	Common environment	Performance characteristics
GNU bc	Older versions of Linux, Cygwin, macOS	The most versatile, but extremely slow when performing large number operations (high scale).
gh-bc (Gavin Howard)	Android (Termux), FreeBSD	extremely fast. Optimized for algorithms and supports modern hardware acceleration.
BusyBox bc	Embedded systems, lightweight Linux	Small size, medium speed, suitable for basic calculations.

4. The ultimate solution: switch to Python testing

If you can't replacebcversion, but if you want to conduct a fair "computing performance test" across different devices, it is recommended to discard it.bc, switch to one that is available on all platforms and implemented consistentlyPython 3. Python's large integer operations are highly optimized, and its performance across platforms is more valuable for reference:

time python3 -c "import sys; sys.set_int_max_str_digits(0); print(2**500000)" > /dev/null

How to confirm the update is successful?

Execute the following command to check the output information:

bc -v: If you see the words "Gavin Howard", it means you have switched to a high-performance version.
which bc: Confirm that the system is currently calling/usr/local/bin/bc(new version) still/usr/bin/bc(old version).

Default format for date

Specify output format once

date "+%Y-%m-%d %H:%M:%S"

Common format examples

# year-month-day
date "+%Y-%m-%d"

# hours:minutes:seconds
date "+%H:%M:%S"

# Full format
date "+%Y-%m-%d %H:%M:%S"

Set default format permanently

# Method 1: Define alias in the shell startup file (.bashrc or .zshrc)
echo 'alias date="date \"+%Y-%m-%d %H:%M:%S\""' >> ~/.bashrc
source ~/.bashrc

#Method 2: Create a function (more flexible)
echo 'date() { command date "+%Y-%m-%d %H:%M:%S" "$@"; }' >> ~/.bashrc
source ~/.bashrc

Effect

# Enter directly after setting
date

# will output
2025-09-14 12:34:56

Date and time subtraction calculation

Calculate steps using bc instruction

Convert date to seconds. For example, use the `date` command to convert date to Unix timestamp.
Calculate the difference in seconds.
Convert the seconds difference back to day, hour, minute, second format.

Example operation

Suppose we want to calculate the difference between 2025-01-11 15:30:00 and 2025-01-10 12:00:00:

Get the Unix timestamp:


$ date -d "2025-01-11 15:30:00" +%s
1731466200

$ date -d "2025-01-10 12:00:00" +%s
1731384000

Calculate the difference in seconds:
```
$ echo "1731466200 - 1731384000" | bc
82200
        
```
The difference is 82200 seconds.

Convert seconds to days, hours, minutes, seconds:

$ echo "82200 / 86400" | bc # days
0
$ echo "82200 % 86400 / 3600" | bc #
22
$ echo "82200 % 3600 / 60" | bc # points
50
$ echo "82200 % 60" | bc # seconds
0

The result is 0 days 22 hours 50 minutes 0 seconds.

Things to note

When using `date -d`, make sure the entered date is in the correct format.
Unix timestamps are based on UTC, and time zone issues should be paid attention to when calculating.

use now

Calculation steps using bc and now

Use the `date` command to convert the target time and now time (now) to a Unix timestamp.
Calculate the difference in seconds.
Convert seconds difference to day, hour, minute, second format.

Example operation

Suppose we want to calculate the difference between the current time and 2025-01-10 12:00:00:

Get the Unix timestamp:

$ date -d "now" +%s
1731462000 # Assume this is the current time when executing

$ date -d "2025-01-10 12:00:00" +%s
1731384000

Calculate the difference in seconds:
```
$ echo "1731462000 - 1731384000" | bc
78000
        
```
The difference is 78000 seconds.

Convert seconds to days, hours, minutes, seconds:

$ echo "78000 / 86400" | bc # days
0
$ echo "78000 % 86400 / 3600" | bc #
21
$ echo "78000 % 3600 / 60" | bc # points
40
$ echo "78000 % 60" | bc # seconds
0

The result is 0 days 21 hours 40 minutes 0 seconds.

Things to note

`now` represents the current time, and the calculation result will change depending on the execution time.
Please confirm that the system time is set correctly when executing to avoid calculation errors.
If you need to be precise to a different time zone, you can use the `TZ` environment variable to set the time zone.

ip command

Command overview

ipcommand is a powerful and versatile Linux network configuration tool that replaces several tools used in older versions of Linux such asifconfig、route、arpandnetstat）。ipCommand usageiproute2Suite for displaying and manipulating routes, network devices, tunnels, policy routing, etc. Its core advantages are its unified syntax, comprehensive functionality and good support for modern network concepts such as policy routing and multicast.

basic grammatical structure

ipThe basic structure of the command is:

ip [options] [object] [action] [parameters]

OBJECT:Specify the network resource to be operated on, for examplelink(Web interface),addr(IP address),route(routing table) orneigh(Neighbor/ARP table).
Action:Specify the action to perform on the object, for exampleshoworlist(show),add(newly added),del(delete).

Main objects and common actions

1. ip addr (IP address management)

action	illustrate	example
show / a	Displays IP address information for all network interfaces.	`ip addr show`
add	Adds an IP address to the specified network interface.	`ip addr add 192.168.1.10/24 dev eth0`
del	Removes an IP address from the specified network interface.	`ip addr del 192.168.1.10/24 dev eth0`

2. ip link (network interface management)

action	illustrate	example
show / l	Displays the status of the network interface (including MAC address, MTU, etc.).	`ip link show`
set	Set the status or properties of the network interface.	`ip link set eth0 up`(enable interface)
set	Change the MAC address of the network interface.	`ip link set dev eth0 address 00:1A:2B:3C:4D:5E`

3. ip route (routing table management)

action	illustrate	example
show / r	Display the core routing table.	`ip route show`
add	Add a new route.	`ip route add default via 192.168.1.1`(Add default gateway)
del	Delete a route.	`ip route del 10.0.0.0/8 via 192.168.1.1`

4. ip neigh (neighbor table/ARP management)

action	illustrate	example
show / n	Display neighbor table (equivalent to ARP cache).	`ip neigh show`
add	Add a new static ARP entry.	`ip neigh add 192.168.1.10 lladdr 00:11:22:33:44:55 dev eth0`

Loopback interface

Interface definition

Loopback interface (usually named on Linux systemslo) is a special, virtual network interface. It is not a physical hardware device, but is completely implemented at the software level by the network stack of the operating system. Its main function is to immediately direct network traffic sent to a specific IP address back to the sending host without going through any physical network interface or external network.

Private IP address

The Loopback interface is associated exclusively with a set of reserved IP addresses:

IPv4： 127.0.0.0/8Network segments, the most commonly used of which are **127.0.0.1**, often calledlocalhost。
IPv6： **::1**, this is alsolocalhostCorresponding address in IPv6.

Any traffic on these addresses is handled at the Transport Layer of the TCP/IP stack and directed back to the application layer, never leaving the host system.

Main uses and functions

Self-testing and debugging:Applications can connect to127.0.0.1to test its network capabilities without worrying about physical network connections. If an application cannot connect to127.0.0.1service, it indicates that there is a problem with the service or the local network stack itself.
Local Service Newsletter:Used for communication between different applications or services (such as client and server programs) on the same host. This ensures communications are private, high-performance, and unaffected by firewall rules or external network delays.
Force local connection:Many network services, such as databases or the management interface of a local web server, are configured to only listen for connections on the Loopback interface to ensure that they can only be accessed from the local host, thus increasing security.
Network stack initialization:In many operating systems, the Loopback interface is a fundamental component necessary for the proper functioning of the TCP/IP protocol stack.

Interface features

characteristic	illustrate
Link Type	`loopback`(No`ether`)
MAC address	Disembodied MAC address, usually shown as`00:00:00:00:00:00`
MTU (Maximum Transmission Unit)	Usually set to the maximum value of 65536, which is much larger than the 1500 of physical Ethernet.
state	Typically remains at system startup`UP`state.

Linux network interface name

Overview

In Linux systems, the name of the Network Interface is used to identify and configure network connections. Although $\text{eth0}$, $\text{eth1}$, etc. are traditionally common, in newer releases, due to the adoption of the "Predictable Network Interface Names" mechanism, the names may become $\text{enp0s3}$, $\text{eno1}$ or other hardware or firmware-based names.

To determine the name of the network interface your system is currently using, you can use a few common commands:

---

Method 1: Use the ip command (recommended)

The $\text{ip}$ command is the go-to tool for network configuration and inspection on modern Linux systems. It lists the details of all network interfaces.


ip a

Result analysis

Each numbered block in the output represents an interface.
You'll see things like $\text{1: lo: ...}$ (the loop interface, usually ignored) and $\text{2: eth0: ...}$ or $\text{3: enp0s3: ...}$ etc.
**Active Interface Identification:** Looks for blocks under interface names (e.g. $\text{eth0}$ or $\text{enp0s3}$) that have $\text{inet}$ (IPv4) addresses assigned to them. This is usually the interface you are currently using to connect to the Internet.
A label next to an interface, such as $\text{\lt}$UP,LOWER\_UP$\text{\gt}$, indicates that the interface is started and connected.

---

Method 2: Use ifconfig directive (Older but still available)

On some older or leaner systems, $\text{ifconfig}$ is still a common tool. In many new distributions it has been replaced by the $\text{ip}$ directive and may need to be installed separately.


ifconfig

Result analysis

The output lists the name of each interface (such as $\text{eth0}$ or $\text{enp0s3}$) and its configuration information.
Similar to $\text{ip a}$, looks for interfaces that have $\text{inet addr}$ (IPv4 address) assigned to them.
If you want to exclude loop interfaces ($\text{lo}$), you can use the command $\text{ifconfig | grep -v lo}$.

---

Method three: View the /sys/class/net directory

The network interface name in Linux systems actually corresponds to a subdirectory under the $\text{/sys/class/net}$ directory. You can list the contents of this directory directly to see the names of all interfaces.


ls /sys/class/net

Result analysis

This command will list the names of all network interfaces (including physical network cards, virtual interface $\text{lo}$, etc.).
This is a simple and fast way to get a list of all interface names.

---

Apply to your directive

Once you have determined the correct interface name, for example it is $\text{enp0s3}$, you can replace it in your directive:


sudo ./gev_nettweak enp0s3

Ubuntu UI Ethernet Management

Network management system

In Ubuntu desktop versions, the graphical tool for managing network connections is NetworkManager. It provides a user-friendly interface that allows users to configure and monitor Ethernet connections without entering commands.

Graphical interface navigation

Users can access Ethernet network settings in the desktop environment by following these steps:

Click the system status menu in the upper right corner of the screen (such as the combination area of network, volume, and power icons).
Find and click the "Settings" icon or option in the drop-down menu.
In the left navigation bar of the system settings window, select Network or Connections.

Ethernet connection configuration

In the Network panel, the Ethernet interface displays its current status. Click the connection name or the gear icon (⚙️) next to it to open the detailed configuration window of the connection, which contains the following main tabs:

Details
- Displays the name of the connection, the network interface name (such as enpXsY or eth0), the connection speed, and the interface's hardware address (MAC address).
IPv4 settings
- Method: Decide how to obtain the IP address.
  - Automatic (DHCP): The system dynamically obtains all network information (IP, subnet mask, gateway) from the DHCP server in the network. This is the default option.
  - Manual: The user manually enters the static IP address, network mask, and default gateway.
- DNS: You can choose to obtain a DNS address automatically, or manually specify one or more DNS servers.
IPv6 settings
- Similar to IPv4, automatic (SLAAC/DHCPv6) and manual configuration options are available.
Security
- Used to set advanced connection authentication protocols, such as IEEE 802.1X, mainly used in protected enterprise or academic network environments.

Integration of underlying systems

On Ubuntu desktop, NetworkManager is the main management service, which stores configurations in dedicated files (usually/etc/NetworkManager/system-connections/). Although modern Ubuntu systems also use netplan as an abstraction layer for their network configuration (its configuration files are located in/etc/netplan/), but in a desktop environment, the graphical interface operations provided by NetworkManager usually override or take precedence over netplan settings, unless the netplan file is configured to cause NetworkManager to ignore the interface.

Set IP permanently in Ubuntu

Set up static IP using Netplan

In Ubuntu, network settings are stored in/etc/netplan/YAML file in the directory. You need to edit this file to apply permanent settings.

1. Query the name of the network interface

Enter the following command in the terminal to confirm the name of your network card (for exampleeth0orenp0s3）：

ip link show

2. Edit Netplan configuration file

Open the profile using a text editor such as nano. File names may vary from system to system, usually ending with.yamlending:

sudo nano /etc/netplan/01-netcfg.yaml

3. Modify YAML content

Modify the content to the following format (note the indentation, YAML is very sensitive to spaces):

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      dhcp4: no
      addresses:
        - 192.168.1.100/24
      gateway4: 192.168.1.1
      nameservers:
        addresses: [8.8.8.8, 8.8.4.4]

4. Apply settings

After saving and exiting the editor, execute the following command to make the settings take effect immediately:

sudo netplan apply

Check variables and status

Check current IP address:
```
ip addr show
```
Check the default gateway:
```
ip route show
```

Things to note

If you are using the desktop version of Ubuntu, your network may beNetworkManagermanage. In this case, you can also use the graphical interface ornmclicommand to set. The above Netplan method is mainly suitable for server versions or situations where underlying fixed settings are required.

Cygwin

What is Cygwin

Cygwin is an emulation layer that provides a Linux/Unix environment for Windows. It contains:

A POSIX-compliant execution environment
Rich GNU/Linux tools (such as bash, gcc, make)
Supports shell script, C/C++ compilation, Unix-style paths and permissions

Download and install

Go to the official website:https://www.cygwin.com/
downloadsetup-x86_64.exe(64 bit)
Run the installer and select:
- Installation path (recommended to be preset)
- Installation source (it is recommended to choose the network)
- Mirror site (select the nearest country)
During the package selection stage, you can select common tools according to your needs:
- bash、coreutils:Basic instructions
- gcc、make: Development tools
- openssh、wget：Network tools

Basic usage

After the installation is complete, open "Cygwin Terminal" to use a Linux-like bash shell.

ls # List directory contents
cd # change directory
pwd # Display the current path
gcc # Compile C program
make # Compile project

File system correspondence

Cygwin root directory/Corresponds to the Windows installation directory (such as C:\cygwin64)
Windows disk starts with/cygdriveBeginning, for example:
- C:\ → /cygdrive/c
- D:\ → /cygdrive/d

Install or add a package

To add a new package, re-executesetup-x86_64.exeand check the required tools. It can also be used with the installation script through the command line.

Common uses

Simulate a Linux development environment on Windows
Use shell scripts to automate workflows
Compile Unix code and perform cross-compilation

Things to note

Cygwin is not a virtual machine or a complete Linux system
Limited integration with native Windows apps
If you need to execute Linux natively, consider WSL (Windows Subsystem for Linux)

Linux and Cygwin

Basic introduction to Linux

Linux is an open source operating system originally created by Linus Torvalds and built on UNIX design principles. It is known for its stability, security and high degree of freedom, and is widely used in servers, desktop environments and embedded devices. Many well-known Linux distributions such as Ubuntu, Fedora, and Debian, offer different desktop and system environments to meet the needs of various users.

Main features of Linux

Open Source:The Linux program code is open to the public, allowing anyone to view, modify and distribute it freely.
Multi-user and multi-tasking:Linux supports a multi-user environment and the simultaneous execution of multiple applications, making it suitable for servers and high-performance applications.
High security:Linux's permissions and account control mechanisms can effectively prevent malicious programs and attacks.
Strong community support:The Linux community is active and resource-rich, and users can easily obtain support and resources.

Basic introduction to Cygwin

Cygwin is a simulation environment that runs on Windows and is designed to provide UNIX-like functionality. It establishes a POSIX-compliant layer that enables users to execute Linux commands and applications in a Windows environment. Cygwin contains a large number of GNU tools and development environment facilitate developers to conduct cross-platform development on Windows.

Key features of Cygwin

UNIX-like environment:Cygwin provides Windows users with an operating experience close to UNIX, allowing the execution of most Linux commands.
Development and porting tools:Cygwin provides the GCC compiler, Make tools, etc., which can port Linux applications to the Windows environment.
Easy installation:Cygwin can be installed through an installation package, and you can freely choose the required software package.
Integrate Windows environments:Cygwin can call Windows system functions, allowing Linux tools to work with Windows applications.

Differences between Linux and Cygwin

Linux is a complete operating system, while Cygwin is just a simulation environment on Windows. Linux provides complete kernel and file system support, while Cygwin relies on the Windows kernel for execution. Although Cygwin can simulate most Linux commands, but differ from Linux in performance and system-level operation.

When to choose Linux or Cygwin

Develop servers and high-performance applications:If you need to run on a server or high-performance computing environment, Linux is a more suitable choice.
Simulate a Linux environment on Windows:If you primarily use Windows but need to use Linux tools and commands, Cygwin provides a good choice.
Learn Linux commands:For newbies, Cygwin is a great tool for learning basic Linux commands.

Managing Cygwin installation packages - in cmd line

Check available packages

In Cygwin, you can usecygcheckTool queries installed packages. This tool allows you to check package names, dependencies and other detailed information, making it easier for users to manage installed packages.

Command example to query suite:

cygcheck -c <package_name>

List all installed packages

If you want to list all installed packages in Cygwin, you can usecygcheck -cOrder. This command will list all installed packages and their status.

Command to list installed packages:

cygcheck -c

Check whether the specified package is installed

To check if a package is installed, you can usecygcheck -cSpecify the package name to check. For example:

cygcheck -c curl

The above command will checkcurlThe installation status of the package.

Install new packages

To install a new package in Cygwin, use the installer setup.exe. Installation can usually be done using setup.exe from the command line. For example, installcurlThe instructions are:

setup-x86_64.exe -q -P curl

This command will install in unattended modecurlkit. If it is a 32-bit system, you need to usesetup-x86.exe。

Tips for using the command line management suite

Install multiple packages:Multiple packages can be specified at once during installation, e.g.setup-x86_64.exe -q -P curl,wget。
Find the package name:If you are not sure about the complete name of the package, you can first use Cygwin's website to search, or use related commands to query.
Update kit:You can choose to update all installed packages when installing new ones to keep your system up to date.

Cygwin official performance testing tool

The following tools are available directly through Cygwinsetup-x86_64.exeInstallation does not require manual compilation, and provides performance evaluation capabilities for CPU, I/O and memory respectively.

1. Bonnie++ (file and hardware I/O testing)

This is the closest to Sysbench included in Cygwin’s official collectionfileioA model tool specifically designed to test disk read and write speed and file creation performance.

Installation name：bonnie++
Main purpose: Test large file reading and writing (compared with cache performance) and the number of file operations that can be performed per second.
Common commands：
bonnie++ -d /tmp -u root

2. Iozone (Integrated File System Test)

Iozone is an extremely professional file system benchmarking tool that supports multi-threaded read and write tests, and its functions are even more detailed than Sysbench's fileio.

Installation name：iozone
Main purpose: Test the read, write, reread, rewrite, and random read and write performance under different block sizes (Record size).
Common commands：
iozone -a -g 1G(Auto mode, tests files up to 1GB)

3. Coreutils built-in tools (basic computing test)

If you just want to simply test the CPU operation speed, you can use Cygwin's built-in instructions to perform logical operation tests.

Command example：time echo "scale=5000; 4*a(1)" | bc -l
illustrate: This will take advantage ofbcCalculate Pi (PI) to 5000 digits and passtimeThe instruction calculates the time consumed by the CPU.

4. Hdparm (quick check of disk performance)

AlthoughhdparmThere are more limitations at the bottom of Windows, but in Cygwin it can still be used to view the cache read speed of the disk.

Installation name：hdparm
Common commands：hdparm -Tt /dev/sda

Tool function comparison table

Sysbench functional block	Cygwin official recommended alternative
CPU (Prime operation)	`bc`(calculate pi) or`factor`(Decomposition of large numbers)
FileIO (disk read and write)	`bonnie++`or`iozone`
Memory (memory bandwidth)	Cygwin official library lacks direct tools, it is recommended to use`dd`Test /dev/zero write speed
Threads (thread scheduling)	Installable`perl`or`python3`Run a simple concurrent loop script

Usage suggestions

Thanks to Cygwin/dev/The device path corresponds to the physical disk of Windows. When performing I/O testing, it is recommended that the path points to/cygdrive/c/temp/to ensure it is running on a physical disk. If you are pursuing 100% the same benchmark data as Linux, it is recommended to useWSL2, where you can directly install the nativesysbench。

WSL 2

How WSL 2 works

WSL 2 is the latest architecture of Windows Subsystem for Linux. Unlike the first generation, which translated Linux system calls into Windows core instructions, WSL 2 includes a real Linux kernel maintained by Microsoft. It operates on lightweight virtualization technology (Hyper-V) and provides complete system call compatibility.

WSL 2 and Cygwin differences

The logic of these two tools for running Linux software on Windows is essentially different:

characteristic	WSL 2	Cygwin
core technology	Lightweight virtualization versus a real Linux kernel.	Recompile Linux tools into native Windows binaries.
Binary compatibility	Native ELF binary files (such as Ubuntu compiled files) can be executed directly.	Only software compiled for the Cygwin runtime environment can be executed.
File system performance	Extremely fast within Linux; access across Windows boundaries is slow.	It operates directly on the Windows file system and accesses Windows files at an average speed.
Hardware acceleration	Supports GPU acceleration (NVIDIA CUDA) and direct access to the network layer.	Direct access to underlying hardware and complex network filtering are not supported.
Docker support	Perfect execution of the Docker container engine.	Docker engine is not supported and can only execute client tools.

WSL 2 Performance Advantages

Because WSL 2 uses real cores, it is typically 2 to 20 times faster than the first generation of WSL when performing disk-intensive tasks such as decompressing source code, executing a compiler, or git clone. This makes it the preferred environment for Windows developers today.

System requirements and installation

WSL 2 requires Windows 10 (2004 and above) or Windows 11. In the latest system, you can directly execute the following command to install through PowerShell with administrator rights:

wsl --install

Select suggestions

If you need a development environment that is exactly the same as the server environment, or if you want to perform AI training or Docker containers, WSL 2 is the standard choice. If you only occasionally need simple tools such as grep or awk to process text files on Windows, and do not want to turn on the virtualization layer, Cygwin or MSYS2 still has the advantage of being lightweight.

iOS system

What is iOS?

iOS is a proprietary operating system developed by Apple for its mobile devices such as iPhone and iPad. It debuted in 2007 with the release of the first iPhone and has become one of the most popular mobile operating systems in the world.

Main features

Simple and intuitive user interface:iOS is known for its smooth and easy-to-use design.
High performance and stability:Provides excellent system stability and performance for Apple devices.
App Store Ecosystem:There are millions of apps available to meet every need.
Strong security:Includes data encryption, Face ID, Touch ID and regular security updates.

Common uses

iOS devices are widely used for a variety of daily and professional needs such as:

Communication: Stay connected with family and friends using Messages and FaceTime.
Work: Complete work tasks with productivity tools like Pages, Numbers, and Keynote.
Entertainment: Use Apple Music, Apple TV, and a variety of gaming apps.
Health: Track health data and exercise records through the health app.

Version history

Every update to iOS brings new features and improvements. For example:

iOS 7：Introducing a new flat design.
iOS 11：Supports augmented reality (AR) technology.
iOS 14：Added new home screen widgets and App library.
iOS 17：Improve system performance and introduce more privacy protection features.

Conclusion

iOS is a constantly evolving operating system that strives to provide users with the best experience and seamlessly integrates with Apple hardware, making it one of the leaders in mobile devices.

Check device information in iOS

Method 1: Use the Settings app

Open thesettingsapp.
Scroll down and clickgenerally。
chooseAbout this machine。
The device model can be found in the Model Name or Model Number fields.

Method 2: Use the support page of Apple’s official website

Note the model number shown on the back of the device or in About This Mac, for exampleAxxxxFormat.
Go to Apple's official device support page.
Search for the model number to confirm device details.

Method 3: Use a third-party application

Download asLirum Device Info Liteand other third-party applications that can view detailed information such as the device model, processor, memory, etc.

Method 4: Query by serial number

existsettingsFind the device's serial number in "About This Mac."
Go to Apple's official websiteService and WarrantyQuery page.
Enter the serial number to get information about the device.

ChromeBook

ChromeBook shortcut key list

Ctrl + Search + S:Show all shortcut keys.
Ctrl + Alt + ?：Helper that displays all available shortcut keys.
Ctrl + Shift + Q (twice):Sign out of your account.
Ctrl + Alt + T：Open the Chrome OS terminal.
Ctrl + Shift + L：Lock screen.
Ctrl + Tab：Switch to the next tab.
Ctrl + Shift + Tab：Switch to the previous tab.
Ctrl + W：Close the current tab.
Ctrl + Shift + T：Reopen the recently closed tab.
Ctrl + Shift + N：Turn on incognito window.
Alt + Tab：Switch open applications.
Ctrl + Alt + Up Arrow：Switch to the previous virtual desktop.
Ctrl + Alt + Down Arrow：Switch to the next virtual desktop.
Shift + Alt + M：Open the Files application.
Ctrl + Shift + Refresh：Rotate screen orientation.
Ctrl + Shift + Plus（+）：Enlarge the screen.
Ctrl + Shift + Minus（-）：Zoom out.
Ctrl + Alt + Z：Turn screen reading on or off.
Ctrl + Alt + Brightness Up：Enter mirror mode (project screen).

Chromebook installs new apps

Overview

Chromebooks use Chrome OS and can install apps from multiple sources, including the Google Play Store and the Chrome Web Store. Users can also enable the Linux (Beta) feature to install Linux Applications to meet different work and entertainment needs.

Install apps from Google Play Store

Click the "Launcher" icon in the lower left corner of the screen.
Search for "Play Store" and click to enter.
Enter the app name or category in the search bar.
Once you find the app you want, click Install.
After the installation is complete, the application will appear in the "Launcher" and can be opened by clicking on it.

Install extensions from the Chrome Web Store

Open the Chrome browser.
Go toChrome Web Store。
Search for the extension or app you want.
Click "Add to Chrome" on the apps page.
After you confirm installation, the extension will appear in the Chrome toolbar or app list.

Enable Linux (Beta) and install Linux applications

Chromebooks support Linux (Beta) features, allowing you to install and run Linux applications, increasing the functionality of the system.

Open the Settings app.
Click "Linux (Beta)" in the left menu and select "Enable".
Follow the on-screen instructions to perform installation settings.
After the installation is complete, use the Linux terminal to enter commands such assudo apt install [application name]to install the software.

Install apps from third-party sources

While the main apps are from the Google Play Store and Chrome Web Store, Chromebooks also support the installation of APK files. Please note that installing applications from third-party sources may present security risks.

Go to Settings and select Security & Privacy.
Enable "Allow installation of applications from unknown sources".
Download the APK file and open it with a file manager to install.

Conclusion

Chromebooks offer multiple ways to install apps to meet the needs of different users. Through the Google Play Store, Chrome Online App Store, and Linux (Beta) features, users can easily expand the functionality of their devices to improve productivity and user experience.

ChromeOS Crostini Shortcut Path

Preset path analysis

In ChromeOS's Linux virtual environment (codenamed Crostini), when you open Terminal, the default location is indeed~(Right now/home/yourusername). However, Crostini is a standalone container with a directory structure separate from the ChromeOS native Downloads or My Files.

Confirm current path

You can enter the following command to confirm the current absolute path:

pwd

If it shows/home/yourusername, then you are in the home directory.

Why can't I find the Desktop folder?

The default Linux environment for ChromeOS isMinimalist installation, it does not automatically build like standard desktop LinuxDesktop、DocumentsWait for the folder. Even if you create it manually~/Desktop, the ChromeOS desktop interface will not display the icons inside, because the integration of Linux containers and the ChromeOS desktop environment is limited to the application menu.

How to create a VS Code shortcut in ChromeOS

Although you cannot place an icon on the ChromeOS desktop, you can make VS Code appear in the ChromeOS Application Launcher (Shelf or Launcher):

1. Confirm .desktop file location

After VS Code is installed, the system should have automatically established an entry point:

ls /usr/share/applications/code.desktop

2. Let ChromeOS recognize the app

if only.desktopFile exists in/usr/share/applications/or~/.local/share/applications/, ChromeOS will automatically add it to the search list. Just press on your keyboardSearch key(search icon), enter "Code" to find it.

3. Pin to the lower toolbar (Shelf)

After finding the VS Code icon, right-click and select"Pin to shelf", this is the "shortcut" method on ChromeOS.

Linux and ChromeOS file interoperability

If you want to access ChromeOS native files on a Linux terminal, the path is as follows:

Location	Path in Linux
home directory (~)	`/home/username`
My Files	`/mnt/chromeos/MyFiles`(You need to right-click on the File App and select "Share with Linux")
Downloads	`/mnt/chromeos/MyFiles/Downloads`

Summary suggestions

In ChromeOS,No need to manually create ~/Desktop, because this directory is not reflected in the ChromeOS desktop interface. Please focus on ensuring/usr/share/applications/code.desktopIf the content is correct, then pin it to the toolbar below through system search.

Chromebook Check CPU and Memory Configuration

Method 1: Diagnose App (system layer, recommended)

Press search key to enterdiagnosis(Diagnostics), or enter it in the address barchrome://diagnosticsTurn on.
View in the "Memory" sectionTotal memorywith immediate usage.

Method 2: chrome://system

Enter in the address barchrome://system, search and expandmem_usage。
mem_usage only displays the usage of each program(e.g. "Browser 208 MB, 547 FDs open of 8192"), There is no direct way to see the total RAM installed on the machine.
If you need total memory, please use the "Diagnostic App" instead (Method 1).

Method 3: Crosh (system shell, observable whole)

according toCtrl + Alt + TTurn on Crosh.
enter:
```
top
```
An overall memory summary (usually shown in MB) is visible at the top of the screen. The display of different models is slightly different.
Also try:
```
memory_test
```
Obtain memory test information (biased towards health test, not necessarily display the exact total).

Method 4: Linux (Crostini) container (for reference only)

Execute in Linux terminal:
```
free -h
grep MemTotal /proc/meminfo
```
Note: What is shown here is the "memory available to the container".Not necessarily equal to the total RAM installed on the actual machine, subject to the "Diagnosis App".

Conversion cheat sheet

If the KB value is obtained (such asMemTotal), conversion formula:
```
GB = KB ÷ 1024 ÷ 1024
```
example:8021236 kB ≈ 8021236 / 1024 / 1024 ≈ 7.65 GB

FAQ

Why can't chrome://system see total memory?Because it only providesmem_usage(Program-level usage), not the total hardware usage.
Where can I see the most accurate total RAM?Using the "Diagnostic App"Total memorynumerical value.

Check CPU and memory usage on Chromebook

Method 1: Use the built-in Task Manager

Chromebooks have a built-in Task Manager that can be used to view the CPU and memory usage of each application.

pressSearch + Esckey to start Task Manager.
In the window that opens, you can see theCPUandmemoryUsage.

Method 2: Via Chrome extension

You can also install Chrome extensions such asSystem MonitororTask ManagerExpand to get more detailed system information.

Open Chrome and go toChrome Web Store。
searchSystem Monitor, and then click the "Install" button.
Once installed, you can enable the tool from the extensions bar and view CPU and memory usage.

Method 3: Using a Linux terminal (if a Linux environment is installed)

If your Chromebook has a Linux environment enabled, you can use Terminal commands to view system resource usage.

Open the terminal and entertopcommand to view the system's CPU and memory usage.
Alternatively, usehtopcommand (if installed) for a more intuitive interface.

Chromebook manages local files

Overview

Chromebooks use the Chrome OS operating system, which focuses on cloud applications but can also manage and access local files. Users can browse, manage and operate files through the built-in "File" application.

Using the Files app

The Files app is your Chromebook's built-in file manager, similar to File Explorer or Finder in other operating systems. Users can view and manage files stored locally on the device or in the cloud in this application.

How to open and use the Files app

Click the "Launcher" icon in the lower left corner of the screen.
Type "file" in the search bar, or select "file" directly from the list of applications.
Once logged in, you can view different file locations in the left panel, such as My Files, Google Drive, and external devices.

Basic file operations

Create a new folder:Right-click any empty space and select "New Folder" to organize your files.
Move or copy files:Drag and drop the file into the target folder, or use right-click to select "Copy" and "Paste".
Rename the file:Right-click the file and select "Rename" to change the file name.
Delete files:Select the file and press the Delete key, or right-click and select "Move to Trash".

Access and manage external devices

Chromebooks support external storage media such as USB devices and SD cards. After inserting the device, it will be displayed on the left panel of the "File" application, and you can directly access and operate the files inside.

Synchronization of cloud and local files

With Google Drive, Chromebook users can easily sync files between the cloud and their computer. This not only provides additional storage space, but also makes it easy to share and access files between different devices.

Conclusion

The Files app for Chromebooks provides a simple and intuitive way to manage local and cloud files. Through it, users can perform basic file operations and access external devices to meet daily file management needs.

Linux terminal for Chromebook

Enable Linux development environment

Open "Settings".
Click "Advanced" > "Developer".
Enable "Linux Development Environment (Beta)".
After the installation is completed according to the instructions, a window calledTerminalapplication.

Features of Linux Containers

Executed in a sandbox environment (Crostini).
The Debian distribution is used by default.
availableaptInstallation kit.
Isolated from ChromeOS file system, files must be shared manually.

Common command examples

sudo apt update
sudo apt install python3
cd ~
ls

Share files with ChromeOS

Open the Files application.
Right-click the folder or file you want to share.
Select "Share to Linux".

After sharing, the terminal can be accessed from the following path:

/mnt/chromeos/MyFiles

Application scenarios

Python, Node.js, C++ and other development environments
Use tools such as Git, Vim, VS Code, etc.
Execute a Linux command line program or shell script

Chromebook's Linux terminal accesses download folder

Share download folder to Linux

Open the file manager (Files).
Right-click on the "Downloads" folder.
Select "Share to Linux".

Access the download folder in a Linux terminal

cd /mnt/chromeos/MyFiles/Downloads

Browse local files

cd /mnt/chromeos/MyFiles
ls

Create symbolic links for quick access

ln -s /mnt/chromeos/MyFiles/Downloads ~/Downloads

It can be used directly afterwards:

cd ~/Downloads

Things to note

Linux containers cannot see local files without setting up sharing first.
You can also share other folders such as "Pictures" and "Documents" to Linux.

Chromebook uses Webapp and Termux to share folders

Step 1: Install Termux

Install on your ChromebookTermuxApp, which can be downloaded and installed from the Google Play Store. Termux provides a fully functional Linux environment for executing commands and managing files.

Step 2: Set up shared folders

Chromebook users can use Chrome OS’sLinux (Beta)Function to share folders in the system to the Linux environment. The setting steps are as follows:

Click on the lower right corner of the Chrome OS system to entersettings。
chooseLinux (Beta), and after turning it on, clickManage shared folders。
Select the folder to share and allow Linux access.

Step 3: Access shared folders in Termux

In Termux, you can access shared folders by mounting the folder. Execute the following commands to browse and mount the shared folder:

cd /mnt/chromeos/MyFiles/Downloads

The above command will direct the user to the Chrome OSDownloadsfolder, or adjust based on the actual shared folder path.

Step 4: Create a webapp to access the folder

On Chromebooks, when you use web technologies such as PWA to create a webapp, you can set the application to access files in the same folder through code such as JavaScript.

// JavaScript example: list folder contents
fetch('/mnt/chromeos/MyFiles/Downloads')
  .then(response => response.text())
  .then(data => console.log(data));

in conclusion

Through the above steps, users can successfully set up a shared folder between Webapp and Termux on Chromebook to achieve file synchronization and access.

Solution to Termux unable to find /mnt/chromeos on Chromebook

Problem description

In some cases Termux may not be able to find/mnt/chromeospath, meaning users cannot directly access the Chrome OS file system. If this happens, you'll need to consider other ways to share files.

Solution 1: Alternative to using Termux to access shared folders

If not available/mnt/chromeos, you can achieve folder sharing with Chrome OS through the following methods:

useTermux APIpackage to access files within Android.
Copy the file from Chrome OS to a path accessible by Termux, such as/storage/emulated/0/(i.e. Android's "internal storage space").

Solution 2: Move the file manually

If Termux cannot directly access the Chrome OS file system, you can manually move the files from the Chrome OS File Manager to a folder that Termux can read and write, such as:

downloadfolder
Play fileTable of contents

Users can copy or move files to these locations through a file manager so that Termux can access them.

Solution 3: Use cloud sync

Another solution is to use a cloud service (e.g. Google Drive, Dropbox) to sync files to Termux. For example:

Upload files to the cloud.
Using TermuxwgetorcurlDownload the archive.

Command example

# Use Termux to access internal storage
termux-setup-storage
cd /storage/emulated/0/Downloads

This will allow Termux to gain access to the internal storage, allowing files to be read and written to that path.

in conclusion

If cannot be found/mnt/chromeosPath, users can solve file sharing problems through other accessible paths or using cloud synchronization.

Chromebook install bc calculator

The most orthodox and stable way to use the bc command on a Chromebook is through the built-in Linux development environment. The following are the specific installation and usage steps:

1. Enable Linux development environment

If the Linux function has not been enabled, please follow the following path:

Open your Chromebook's settings.
Select Advanced from the menu on the left, then click Developer.
Find the Linux development environment and click to open it.
Follow the window prompts to complete the installation.

2. Execute the installation instructions

Open Terminal in the application launcher and enter the following commands in sequence:

# Update software package list
sudo apt update

# install bc
sudo apt install bc -y

3. Verification and basic operations

After the installation is complete, you can enter bc directly in the terminal to enter calculation mode. Commonly used techniques are as follows:

Function	Command example
Start and include the math function library	bc -l
Set the number of decimal places	After entering, enter scale=4
Quickly calculate and exit	echo "10/3" \| bc -l
Exit interactive mode	Type quit or press Ctrl+D

Through the above steps, you can call this high-precision calculation tool at any time in the Linux terminal of your Chromebook.

Install Emacs on Chromebook

Enable Linux (Beta) features

Before you can install Emacs on your Chromebook, you first need to enable the Linux (Beta) feature. Linux (Beta) provides an environment for running Linux applications on Chromebooks.

Open your Chromebooksettings。
Scroll down and findLinux (Beta)。
Clickenablebutton and follow the prompts to complete the installation.

Update Linux packages

After installing the Linux environment, it is recommended to update the system software package first to ensure that Emacs can be installed smoothly.

sudo apt update && sudo apt upgrade

Enter the above command in the terminal and pressEnterkey.

Install Emacs

After completing the system update, you can install Emacs. Please enter the following command and pressEnter：

sudo apt install emacs

Emacs will be downloaded and installed automatically. After the installation is complete, you can enter in the terminalemacsto start Emacs.

Install Snap (optional)

If you want to get a newer version of Emacs, you can install it using the Snap package manager. First, you need to install Snap:

sudo apt install snapd

Next, use Snap to install Emacs:

sudo snap install emacs --classic

This will install the latest version of Emacs.

Start Emacs

After the installation is complete, you can start Emacs by following these steps:

Enter in the terminalemacsand pressEnter。
Or find Emacs in your Chromebook's application list and click Start.

FAQ

If you encounter any errors during the installation process, it is recommended to check whether the network connection is stable and ensure that the Linux (Beta) feature is enabled and the system is updated.

Chromebook opens .ods files

1. Use Google Sheets

Chromebooks come pre-installed with Google Sheets and support opening .ods files.

Upload the .ods file on Google Drive.
Right-click the file and select "Open with Google Spreadsheet."
.ods files can be edited directly or saved as .xlsx or Google Sheets format.

2. Using LibreOffice (Linux environment)

Install LibreOffice through the Chromebook's Linux development environment to open .ods files.

Enable Linux (Settings > Advanced > Developer > Linux Development Environment).

In the Linux terminal enter:

sudo apt update
sudo apt install -y libreoffice

After the installation is complete, open LibreOffice Calc and open the .ods file.

3. Use online tools

There is no need to install software, you can use online tools to open .ods files.

4. Use Android Apps

Some Chromebooks support Android applications and can install OpenOffice related apps.

Install the app on Google Play Store.
Open the app and select the .ods file to edit.

in conclusion

Best way:Google Sheets (no software installation required)
Full functionality:LibreOffice (installed via Linux)
Quick view:Online tools
Mobile version options:Android App

flat

Common tablet gestures

Click:Touch the screen with one finger, usually to open applications and select items.
double click:Two quick taps with one finger are typically used to zoom in or out on a picture or file.
Long press:Press and hold a location on the screen for a few seconds, often used to open function menus or move application icons.
slide:Use one finger to hold and drag to turn pages, browse long lists, or move objects.
Pinch to zoom:Use two fingers to pinch inward or outward on the screen, often used to zoom in and out of photos and maps.
Three-finger swipe:Swiping up with three fingers at the same time usually opens Multitasking Manager.
Four fingers together:Use four fingers to pinch inward to quickly return to the home screen.
Two-finger rotation:Use two fingers to rotate on the screen, suitable for rotating pictures.

Chromebook using VS Code

Environment overview

Through the built-in Linux container (Crostini), Chromebook can create a development environment similar to Debian and install a variety of development tools such as VS Code, Python, Node.js, etc. If the hardware specifications are sufficient, it can carry out general Web, Python, C/C++ and other development work.

Common development methods

Native Linux containers:After enabling Crostini, install tools such as VS Code, Git, Node.js, etc.
Cloud IDE:Use cloud platforms like GitHub Codespaces, Replit, StackBlitz, and more.
Web version VS Code:Open directlyvscode.devUse, no installation required.

Enable Linux containers

Enter Chromebook Settings → "Developer" → "Enable Linux Development Environment (Beta)" → Terminal will appear after completion. Execute in terminal:

sudo apt update && sudo apt upgrade -y

Install VS Code

Download the official package and install:

wget -O vscode.deb https://update.code.visualstudio.com/latest/linux-deb-x64/stable
sudo apt install ./vscode.deb
code

Dependency error during installation

If errors such as "libc6:amd64 not installable" occur, the usual reasons are as follows:

Containers are 32-bit or ARM architecture (not x86_64)
APT suite origin is not contrib/non-free enabled

Check schema

Enter in the terminal:

uname -m

Description of results:

x86_64：For 64-bit Intel/AMD architecture, .deb can be installed directly
aarch64：For ARM architecture, you need to use ARM version or VSCodium instead.

ARM architecture solution

If aarch64 is displayed, the official VS Code x64 installation package cannot be used. Use one of the following methods instead:Option 1: Official ARM64 version compressed file

cd ~
wget https://update.code.visualstudio.com/latest/linux-arm64/stable -O vscode-arm64.tar.gz
tar -xzf vscode-arm64.tar.gz
cd VSCode-linux-arm64
./code

Option 2: VSCodium (open source version)

sudo apt install -y curl gpg
curl -fsSL https://gitlab.com/paulcarroty/vscodium-deb-rpm-repo/raw/master/pub.gpg \
 | sudo gpg --dearmor -o /usr/share/keyrings/vscodium-archive-keyring.gpg
echo 'deb [signed-by=/usr/share/keyrings/vscodium-archive-keyring.gpg] \
https://download.vscodium.com/debs vscodium main' \
 | sudo tee /etc/apt/sources.list.d/vscodium.list
sudo apt update
sudo apt install codium
codium

Option 3: Use VS Code Web Edition
Go directly tohttps://vscode.devUse, no installation required.

Recommended choice

Usage context	Suggestions
Hope offline development, complete functions	Download the official ARM64 compressed version
Want to use package management and automatic updates	Install VSCodium (codium)
Occasional development, quick start	Use vscode.dev

in conclusion

Chromebooks' Linux containers already meet most development needs. If it is x86_64 architecture, you can install the official VS Code directly; If it is ARM (aarch64), it is recommended to use VSCodium or the official ARM64 version compressed file. This makes it easy to create a complete program development environment on your Chromebook.

basic tools

UltraEdit

UltraEdit is a powerful text editor designed for developers and editing professionals. Developed by IDM Computer Solutions, Inc., it supports multiple programming languages and file formats and provides a variety of advanced features to increase productivity.

Main features

Multi-language support:Supports multiple programming languages, including C/C++, Java, HTML, PHP, Python, etc.
File comparison:The built-in file comparison tool facilitates users to check the differences between two files.
Macro recording:Allows users to record and playback macros, simplifying repetitive tasks.
FTP/SFTP support:Files on the server can be edited directly in UltraEdit, supporting FTP and SFTP protocols.
Custom interface:Users can customize toolbars, color themes, and keyboard shortcuts according to their needs.

Basic operations

Here are some basic UltraEdit operations:

Open file:Select in the main menuFile > OpenOr use shortcut keysCtrl + O
Save file:useCtrl + SSave the currently edited file.
Find text:useCtrl + FOpens the Find dialog box.
Replace text:useCtrl + ROpens the replacement dialog box.

in conclusion

UltraEdit is a powerful and flexible text editor suitable for a variety of uses, especially in programming and file management. Its multi-language support and advanced features make it an ideal choice for developers.

Emacs

Emacs is a highly extensible text editor originally developed by Richard Stallman in the 1970s. It is an open source software and supports a variety of programming languages and markup languages, making it a popular choice among programmers and technical writers.

Main features

Scalability:Using the Emacs Lisp language, you can customize and extend the functionality of your editor.
Multiple modes:Emacs supports various editing modes, including text mode, programming mode, HTML and Markdown mode, etc.
Powerful keyboard shortcuts:Emacs is known for its efficient keyboard operation, allowing users to quickly edit text.
Versatility:In addition to editing text, Emacs can also be used to manage emails, calendars, file management, etc.

Basic operations

Here are some basic Emacs operations:

Open file: C-x C-f (Ctrl + x, Ctrl + f)
Save file: C-x C-s (Ctrl + x, Ctrl + s)
Close file: C-x C-c (Ctrl + x, Ctrl + c)
Undo operation: C-/orC-x u(Ctrl + / or Ctrl + x, u)

in conclusion

Emacs is a powerful and flexible text editor suitable for a variety of purposes, whether programming or document editing. It may have a somewhat steep learning curve, but once mastered, it will greatly increase your productivity.

Alternatives to MS Office

1. Google Workspace

The tools provided by Google Workspace include Google Docs (documents), Google Sheets (sheets), Google Slides (presentations), etc., with cloud storage and collaboration functions, allowing multiple users to edit and comment on files at the same time.

2. LibreOffice

LibreOffice is a free and open source office suite that includes Writer (word processing), Calc (spreadsheet), Impress (presentation), etc. It supports a variety of file formats and has a user interface similar to MS Office.

3. WPS Office

WPS Office is an office suite developed by Kingsoft Software. It includes text, form and presentation functions. The free version provides basic functions and supports interoperability with MS Office file formats.

4. OnlyOffice

OnlyOffice is an integrated office suite that supports editing of documents, spreadsheets and presentations, provides collaboration features, and can be integrated with cloud storage services such as Nextcloud.

5. Zoho Office Suite

Zoho Office Suite provides comprehensive applications including Zoho Writer, Zoho Sheet and Zoho Show, and supports seamless integration with other Zoho products, making it suitable for business use.

6. Etherpad

Etherpad is an open source real-time collaborative text editor, suitable for teams to edit documents at the same time, especially suitable for brainstorming or meeting notes.

7. Markdown editor

Markdown editors such as Typora and Obsidian focus on concise text editing and are especially suitable for users who need to quickly edit and format text.

8. Prezi

Prezi is a cloud-based briefing tool that provides dynamic and interactive briefing formats, suitable for users who need innovative presentation methods.

in conclusion

When choosing an alternative to MS Office, you should consider your own needs and usage scenarios. The above tools each have their own characteristics and suit the needs of different users. Whether used by individuals or teams, you can find suitable office tools.

LibreOffice Writer saves PDF files

Use the export function

Open the file you want to export.
Click on the menu abovefile。
chooseExport as > Export to PDF。
In the "PDF Options" window that opens, you can adjust settings according to your needs, such as compression, tags, password protection, etc.
After setting is complete, pressremitbutton.
Select the storage location and name the file, clickstorePDF will be generated.

Quick toolbar export

You can also directly click on the toolbarExport to PDFicon (the icon is a small PDF image), quickly generate PDF files, using default settings.

Things to note

Please confirm that the content has been saved before exporting to avoid missing modifications.
If you need to protect PDF files, you can add a password to the export settings.
Supports exporting content including bookmarks, hyperlinks, annotations, etc.

Presentation software

Common free presentation software

LibreOffice Impress: Open source and free, with complete functions and supporting multiple formats (such as .ppt, .pptx).
Google presentation: Cloud service supports real-time collaboration among multiple people and automatic file storage.
WPS Presentation: The interface is similar to PowerPoint, with cross-platform support and a free version.

Common paid presentation software

Microsoft PowerPoint: The most widely used, powerful function, supports animation, macros and various design tools.
Keynote(Apple): Exclusive for Mac and iOS, it has a beautiful design and is suitable for quickly making high-quality presentations.

Online presentation tool

Canva: Provides a large number of templates, suitable for quick production by non-design professional users.
Prezi: Features a non-linear presentation that can increase visual effects by zooming and moving the screen.

Select suggestions

If you want professional and complete functions: choosePowerPoint。
If you prefer free and open source: selectLibreOffice Impress。
If you value multi-person collaboration and the cloud: ChooseGoogle presentation。
If you are pursuing innovative visual effects: choosePrezi。

LibreOffice Calc calculates the hour difference between two times

Method 1: Use formula

Assume the starting time is in the cellA1, the end time is in the cellB1。

Enter the following formula in the target cell:
```
=B1 - A1
```
Set the result cell format to "Time Format" or "Number Format".

If you need to display it in hours, use the formula:

= (B1 - A1) * 24

Method 2: Use the TEXT function

If more precise or specific formatting is required, useTEXTfunction:

=TEXT(B1 - A1, "[HH]")

This will show the pure hour difference between the two.

Things to note

make sureA1andB1The value is in a valid datetime format.
If there is a cross-day situation, the formula can still be calculated correctly.

Calc gets the last value of a column

Use formula method

Suppose you want to get a worksheet in any cellColumn AFor the last non-null value, use the following formula:

=INDEX(A:A;MAX(IF(A:A<>"";ROW(A:A))))

Usage steps

Select the cells where you want the results to appear.
After entering the formula above, pressCtrl + Shift + Enter(Create array formula).
The result is the content of the last non-blank cell in column A.

To specify a worksheet

To copy data from another worksheet such asSheet2) to get the last value in column A, available:

=INDEX(Sheet2.A:A;MAX(IF(Sheet2.A:A<>"";ROW(Sheet2.A:A))))

Simplified version (newer versions of LibreOffice only)

If the version supportsFILTERFunction, also available:

=INDEX(FILTER(A:A;A:A<>"");COUNTA(FILTER(A:A;A:A<>"")))

Formula description

ROW(A:A): Return all column numbers in column A.
IF(A:A<>"";ROW(A:A)): Take only non-blank column numbers.
MAX(...): Get the column number of the last column.
INDEX(A:A;...): Return the last value in column A based on the column number.

If there are gaps in the column, take the last value of the column.

Problem description

you mentionedMAX(IF(A:A<>"";ROW(A:A)))"Incorrect" when there are interspersed spaces in the column. In practice, this type of array formula will have boundary problems for full column references or different data types (text/number mixed). Listed below are several robust practices (including applicable situations and explanations) that you can choose based on the data type and Calc version.

Universal and concise (supports text and numbers, no array input required)

=LOOKUP(2;1/(A1:A10000<>"" ); A1:A10000)

Description: withLOOKUPmatch1/(A<>"")Find the last non-null value. Rather than referencing the entire column, it is recommended to limit the range to a reasonable upper limit (for example: A1:A10000) to avoid performance or compatibility issues.
Advantages: Supports both text and numbers, no need to pressCtrl+Shift+Enter。

Only numbers (quickly get the last value)

=LOOKUP(9.99999999999999E+307; A1:A10000)

Note: This is the traditional Excel/Calc method. Only the last value will be returned. If there is text in the column, it will be ignored.

If you want to get the last non-empty column number (and accept array formulas)

=MAX(IF(A1:A10000<>""; ROW(A1:A10000) ))

Note: When this formula is correct, it will return the column number of the last column, but the range needs to be limited (do not use the entire column A:A, which may cause problems in some Calc versions).
Usage: After inputting, please enterCtrl+Shift+EnterCreate an array formula (if your version of Calc supports dynamic arrays, you can enter directly).
Get value: reuseINDEXGet the value, for example:
=INDEX(A1:A10000; MAX(IF(A1:A10000<>"";ROW(A1:A10000)))-ROW(A1)+1 )

Replacement: Find the last column number first, then INDEX (more intuitive)

=INDEX(A1:A10000; MATCH(2; 1/(A1:A10000<>"") ))

illustrate:MATCH(2;1/(A<>""))will return the last matching relative position, and thenINDEXGets a value; no array input is required either (some versions may still require array mode).

Example (getting values across worksheets)

=LOOKUP(2;1/(Sheet2.A1:A10000<>"" ); Sheet2.A1:A10000)

BundleSheet2Change the range to your actual worksheet with a reasonable upper limit.

Practical suggestions

Avoid using full column imagesA:Aas a reference for array functions; use a reasonable upper limit instead e.g.A1:A10000, to avoid performance or compatibility issues.
If the data will exceed the upper limit, increase the upper limit; but do not use the entire column for reference without limit.
If only the last digit is usedLOOKUP(9.99E+307,…), for text or mixed data please useLOOKUP(2;1/(…);…)。
Test the range and whether you need to press theCtrl+Shift+Enter。

LibreOffice Calc move bar and keep reference

Use drag and drop (suitable for simple data)

Select column G:
- Click the field heading "G" to select the entire field.
Drag to new location:
- Press and holdAltkey (keep formula reference).
- Drag column G between columns B and C. (Click on the column value to drag, not on the column title)
- Release the mouse button when the vertical line appears.

✅ References will be updated automatically.

Use cut and insert (for complex formulas)

Select column G:
- Click the field heading "G" to select the entire field.
Cut fields:
- according toCtrl + X(Windows/Linux) orCmd + X（Mac）。
Insert cut fields:
- Right-click on column C and select "Insert Cut Cells".

✅ Formula references will automatically remain correct.

Using copy and paste (for manually adjusting references)

Select column G and pressCtrl + C(Windows/Linux) orCmd + C（Mac）。
Select column C and pressCtrl + V(Windows/Linux) orCmd + V（Mac）。
If the reference is not updated automatically, use Find and Replace:
- according toCtrl + HTurn on find and replace.
- looking for$G, replaced by$C。
- Click "Replace All".

in conclusion

Drag method:For simple data, hold Alt to maintain reference.
Cut and insert:Best suited for fields with formulas, the reference will update automatically.
Copy and paste:The reference needs to be adjusted manually to suit specific needs.

Calc title bar hides sort drop-down button

Reason for occurrence

In LibreOffice Calc, if the "AutoFilter" or "Filter" function is enabled, a drop-down arrow will appear next to each field name in the title bar, which can be used to sort or filter.

How to cancel drop-down button

Select the title bar range with the drop-down arrow.
Click on the menu abovematerial。
chooseAutomatic filtering（AutoFilter）。
After clicking again, the drop-down arrow will be closed.

Other related operations

If usingProfile > Filters > Standard Filters, the drop-down arrow will not be displayed in the title bar.
availableProfile > Remove filter, clear the filter completely.

Things to note

The drop-down arrow is only an additional icon for the filtering function and does not affect the cell content.
After hiding, if you need to re-filter, you can turn on "Auto Filter" again.

Calc sets cell color based on formula

Use conditional formatting to set colors

In LibreOffice Calc, you can use "conditional formatting" to set the color of cells based on formulas.

step

Select the range of cells to which you want to apply the color.
ClickFormat > conditional formatting > condition...。
Select "Formula is" under "Condition 1".
Enter the formula, for example:
- A1>100(Changes color when A1 is greater than 100)
- MOD(ROW();2)=0(Colorize even columns)
Click "Add Style", select a background color and name the style.
Click OK to apply the settings.

Common formula examples

If the cell value is greater than 50, it turns green:
A1>50
If the cell value is empty, it turns gray:
ISBLANK(A1)
If the cell contains specific text (such as "Done"), it turns blue:
A1="Complete"

Things to note

The priority of conditional formatting is from top to bottom, and the condition that is met first will take effect.
When applying a range, make sure the formula is referenced in the correct way (relative or absolute).
Color settings can be modified or deleted through "Manage Conditional Formatting".

Calc dynamic column reference

Determine column number based on cell contents

In Calc, likeA$534This way of writing fixes column 534A534Cell.
If you want the column number "534" to be determined by the value of other cells (for example, the cellB1content is 534), you can useINDIRECT (indirect reference)function.

example

=INDIRECT("A"&B1)

hypothesisB1 = 534
The above formula is equivalent to=A534

Cross-sheet example

=INDIRECT("'Sheet2'.A"&B1)

It can be used across worksheets. Please note that if the worksheet name contains spaces, single quotes must be included.

The matching column number is also dynamic

If both columns and columns are to be specified by cells, for example:

B1 = "C"
B2 = 55

Available:

=INDIRECT(B1 & B2)

The result is equivalent to=C55。

Another way to write the ADDRESS function

If you want to generate the complete address numerically, you can also use:

=INDIRECT(ADDRESS(B2; COLUMN(A1)))

B2: The cell contains the column number (for example, 534)
COLUMN(A1): Indicates column 1 (column A)
Can handleA1Change to other columns to specify the column number

Things to note

INDIRECTReferences are not automatically updated when columns are inserted or deleted.
If the reference range is large or used in large quantitiesINDIRECT, which will slightly affect performance.

OpenOffice Calc and HTML table editing

OpenOffice Calc export to HTML table

OpenOffice Calc (spreadsheet program) is not primarily an HTML table editor, but it has the ability to export (or save) spreadsheet content to HTML format, which can generate an HTML table.

Export steps: In Calc, you can select "HTML Document" as the file type through the "File" $\to$ "Save As" or "Export" function.
Result: Calc will convert the selected worksheet or the entire file into an HTML file, with the data wrapped in the standard HTML $\lt$table$\gt$ tag structure.
Limitations: Calc will try to retain basic formats (such as colors, borders) when exporting, but the exported code is usually more complex, and the main purpose is to display data, not for "editable" interaction on the web page.

Calc as an HTML table creation tool

Calc’s excellent spreadsheet function makes it a convenient tool for creating HTML table data and structures:

Create and organize tabular data in Calc using the familiar cell interface.
Design with Calc's features such as merged cells, fonts, and background colors.
Save or export the completed spreadsheet as an HTML file.
You will then need to use a specialized HTML editor or text editor to copy and paste the $\lt$table$\gt$ code output by Calc into your web page project.

Editing HTML tables: Reverse operation (import)

Calc also supports importing existing HTML tables into spreadsheets:

Function: Calc has the "external data" function, which can obtain data from web pages (including tables in web pages).
Operation: Through the "Insert" $\to$ "Link to External Data" or "Web Query" function, you can import table data from an HTML file or web page into the Calc cell.
Editability: Once data is imported into a Calc cell, you can edit and manipulate it using all of Calc's features (such as formulas, sorting, filtering).

Summarize

OpenOffice Calc is not a WYSIWYG HTML editor. It cannot visually edit HTML code directly like professional web editing software. But it can:

Convert spreadsheet data to HTML table code (export).
Import HTML table data into the spreadsheet for editing and processing (import).

HTML table editor

What is HTML table editor?

The HTML table editor is a tool that allows users to easily create, modify and manage HTML tables through a graphical interface or concise syntax. Users usually do not need to write complex $\lt$table$\gt$, $\lt$tr$\gt$, $\lt$td$\gt$ or $\lt$th$\gt$ tags directly. Instead, they can complete table design and data filling by clicking, dragging or typing content.

Editor type

What you see is what you get (WYSIWYG) editor: Provides an interface similar to word processing software, and users can directly see the final rendering of the form for editing.
Code editor built-in features: Many advanced code editors or IDEs (integrated development environments) provide specialized features or extensions to assist in the creation and layout of HTML tables.
Online Generators: Web tools designed to quickly generate HTML table code. They usually provide various options for users to choose, such as borders, cell spacing, colors, etc.

Main functions

Function	describe
Add/delete rows and columns	Quickly add or remove rows or columns anywhere in the table.
Merge cells	Supports the $\text{colspan}$ (spanning columns) and $\text{rowspan}$ (spanning rows) attributes of the $\lt$td$\gt$ or $\lt$th$\gt$ tags.
Style adjustment	Set the border, background color, text alignment, etc. of the table, row, or cell with $\text{CSS}$ styles.
Content editing	Type or paste text, images, or other HTML content directly into the cell.
Code preview/output	Instantly displays the generated HTML source code and provides copy or download capabilities.

How to use (take WYSIWYG editor as an example)

Create a table: Click the "Insert Table" button on the toolbar and set the initial number of rows and columns.
Enter data: Click a cell in the table and enter the required content.
Modify the structure: Right-click a cell and use the options in the menu to add, delete, or merge cells.
Adjust styles: Select the entire table or specific cells and use the Properties panel to adjust styles such as width, color, and borders.

HTML table WYSIWYG editor

Common WYSIWYG editor types

What you see is what you get (WYSIWYG) editor allows users to operate in a visual interface without writing HTML code directly. In terms of "table editing", they usually provide intuitive buttons and menus to insert, modify and merge tables. This type of editor is mainly divided into several forms:

Independent web design software

This type of software is a complete desktop application designed to create and manage an entire website. It contains a powerful WYSIWYG editor function, table editing is just one of its many functions.

Adobe Dreamweaver: This is a well-known professional web design software in the industry, providing powerful visual editing capabilities, including complex table structure creation and style adjustment.
Microsoft Expression Web (discontinued): This is a web design tool launched by Microsoft that inherits the WYSIWYG editing concept of FrontPage.

As part of a content management system (CMS)

Many content management systems (such as WordPress, Joomla!, Drupal, etc.) and e-commerce platforms have built-in WYSIWYG editors in the article or page editing interface. Users can insert and modify tables directly in the background editor.

TinyMCE: This is a very popular open source JavaScript library that many CMS and applications integrate as a built-in editor. It provides a dedicated table function menu for inserting, deleting rows/columns and merging cells.
CKEditor: Another widely used open source WYSIWYG editor. It provides rich table creation and editing tools, including advanced attribute settings.
Gutenberg (WordPress block editor): Although the modern block editor is not entirely traditional WYSIWYG, it provides a dedicated "table block" that allows users to visually edit table content and styles.

Online HTML Generator/Tool

These are tools that run specifically on web pages, and their main purpose is to quickly generate HTML code, including table code. Users set parameters (such as the number of rows, columns, styles) on the web interface, and the tool will instantly generate code for users to copy.

Table Generator-like websites: Many websites provide specialized HTML table generators that allow users to operate tables through a spreadsheet-like interface.

Other application built-in editors

Some desktop applications, such as specific note-taking software or productivity tools, usually have built-in WYSIWYG editing capabilities for processing tables if they support exporting HTML format.

virtual machine software

What is a virtual machine?

Virtual machine is a software technology that can simulate a complete computer system, allowing users to run multiple virtual operating systems on a physical computer. Through virtual machines, you can run different versions of operating systems, such as Windows, Linux, etc., simultaneously on the same hardware.

Advantages of virtual machines

Resource isolation: Each virtual machine has its own independent environment and will not interact with other virtual machines.
Flexible testing: New operating systems or software can be easily tested without affecting the original system environment.
Efficient management: Centrally manage and allocate resources to improve hardware utilization efficiency.

Common virtual machine software

VMware Workstation: A mature and powerful virtual machine software that supports multiple operating systems.
Oracle VirtualBox: Free open source virtual machine software, suitable for individuals and small businesses.
Microsoft Hyper-V: A built-in virtualization solution for Windows systems, applicable to Windows Server and Windows 10 Professional.

Virtual machine applications

Virtual machines are widely used in development, testing, server virtualization, and desktop virtualization. It can help developers conduct software testing in multiple operating system environments, and also provide enterprises with a more flexible server management method.

How to make a system boot disk

What is a boot disk?

A bootable disk is a storage device from which a computer can be booted. It is often used to install operating systems or repair system problems. Common media are USB flash drives or external hard drives.

Preparation

A blank USB flash drive (8GB or above recommended)
ISO image file of operating system (such as Windows, Ubuntu, Fedora, etc.)
Tools for making bootable disks (below)

Common production tools

on Windows

Rufus（rufus.ie): fast, simple, supports multiple formats and modes
balenaEtcher（balena.io): Cross-platform, graphical interface, supports HDD writing
Official Media Creation Tool:Official tool for Windows
Ventoy（ventoy.net): Supports multi-ISO booting, only needs to be written once and can be used repeatedly.

on Linux

ddCommand: Command line tool, fast to write but high risk
balenaEtcher: Graphical operation, simple and convenient
Startup Disk Creator：Ubuntu built-in tools
Ventoy: After installation, copy the ISO directly to start

How to use Ventoy

Download and execute Ventoy
Select the USB device and click "Install"
After the installation is complete, the USB device will be in a special format
Copy multiple ISO files directly to USB (no need to repeat formatting)
Restart and boot from USB, Ventoy will display the ISO menu

Rufus production steps

Turn on Rufus and plug in the USB
Select ISO file
Select boot mode (MBR/GPT)
Click "Start" and wait for completion

Linux dd command demonstration

sudo dd if=~/Downloads/os.iso of=/dev/sdX bs=4M status=progress && sync

/dev/sdXas the target USB device (please confirm the correct path)
Data will be completely erased, please operate with caution

After completion

Plug in the device and reboot
Enter BIOS/UEFI and set boot from USB storage device
You can enter the installation or repair process.

Suggestions and Notes

Creating a bootable disk will clear the USB internal data, so be sure to back it up.
Ventoy is suitable for repeated use and management of multiple systems
The dd command is powerful but risky. Newbies are advised to use Etcher or Ventoy.

Software mall

Software sales platform

In 2026, choosing the right software sales platform will depend on your software type and target market. The following are the classifications and characteristics of mainstream platforms:

Universal digital products and SaaS platforms

Paddle / Lemon Squeezy：The financial custody platform (Merchant of Record) specially designed for software developers can automatically handle complex digital consumption tax and compliance issues in countries around the world.
Gumroad：The interface is minimalist, suitable for individual creators to sell gadgets, plug-ins or scripts, and the threshold for entry is extremely low.
AppSumo：The world's leading software promotion platform is suitable for quickly acquiring a large number of users through the Lifetime License Plan (LTD) in the early stages of new product launches.
Shopify：Through the powerful expansion ecosystem, it can also be transformed into an official brand website that sells software serial numbers and digital licenses.

Game and desktop application distribution platform

Steam：The world's largest PC game mall, with the strongest organic traffic, takes a 30% sales share.
Epic Games Store：Provides a more competitive 12% commission rate, with additional discounts for works developed using Unreal Engine.
itch.io：The first choice for independent developers, it supports free pricing and optional commission ratios, and is suitable for experimental or small and medium-sized projects.

Enterprise and mobile application mall

App Store / Google Play：The only mainstream channel for mobile applications, providing a complete subscription and in-app purchase mechanism.
AWS / Azure Marketplace：Suitable for B2B enterprise software, it allows enterprise customers to purchase and deploy directly through cloud service billing.

Taiwanese local e-commerce platform

SHOPLINE / CYBERBIZ：Provides complete localized cash flow (such as Line Pay, Jiekou Payment), suitable for operating software official websites of local brands in Taiwan.
Shopee shopping:It has huge traffic and is suitable for selling low-price digital tools, serial numbers or teaching files.

Platform selection comparison table

demand target	Recommended platform	Core advantages
Automate global tax processing	Paddle / Lemon Squeezy	Save yourself the trouble of tax declaration in various countries
Pursue maximum traffic	Steam / App Store	Ready-made massive user base
Quickly build a brand official website	Shopify / SHOPLINE	Highly customized shopping experience
Early seed user acquisition	AppSumo	Get cash quickly through promotions

T:0000

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Time format example

pagefile.sys virtual memory paging file management

1. What is pagefile.sys?

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4. Best practices for paging files

View memory configuration

Method 1: Use Windows built-in tools

1. Use Resource Monitor to view

2. Use command prompt characters

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1. Using CPU-Z

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Method 3: Check the physical hardware

Summarize

Performance Monitor PerfMon

How to turn on PerfMon

Core function module

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lodctr

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Common repair scenarios: PerfMon displays abnormally

Things to note

Computing performance test

Core test indicators

Common test types

Commonly used computing performance testing tools

Best practices for testing

Windows Check CPU Temperature and Motherboard Temperature

Use BIOS to view

Using Task Manager

Using Windows PowerShell

Use third-party software

Using the command prompt (CMD)

Abnormal CPU usage and clock speed when the temperature is too high

Check your motherboard model in Windows

Method 1: Using Command Prompt

Method 2: Use PowerShell

Method 3: Use third-party tools

Method 4: Check BIOS or UEFI

Change the file extension of the opener

Edit via File Explorer