Comprehensive Guide to Common Linux Commands

1. File and Directory Operations

Command	Function	Common Parameters	Example
<span>ls</span>	List directory contents	<span>-l</span>(detailed) <span>-a</span>(hidden files) <span>-h</span>(human-readable sizes)	<span>ls -lah /home</span>
<span>cd</span>	Change directory	<span>..</span>(parent directory) <span>~</span>(home directory)	<span>cd ~/Documents</span>
<span>pwd</span>	Display current path	–	<span>pwd</span>
<span>mkdir</span>	Create directory	<span>-p</span>(create parent directories)	<span>mkdir -p project/{src,doc}</span>
<span>cp</span>	Copy files/directories	<span>-r</span>(recursive) <span>-v</span>(verbose)	<span>cp -rv data/ backup/</span>
<span>mv</span>	Move/Rename	<span>-i</span>(prompt before overwrite)	<span>mv old.txt new.txt</span>
<span>rm</span>	Delete files	<span>-r</span>(recursive) <span>-f</span>(force) ⚠️ Use with caution	<span>rm -rf tmp/*</span>
<span>find</span>	Search for files	<span>-name</span>(name) <span>-type</span>(type)	<span>find / -name "*.log"</span>
<span>grep</span>	Text search	<span>-i</span>(ignore case) <span>-r</span>(recursive)	<span>grep -r "error" /var/log</span>

2. Viewing and Editing File Contents

Command	Function	Common Operations
<span>cat</span>	Display file contents	<span>cat file.txt</span>
<span>less</span>	View file page by page	<span>/keyword</span>(search) <span>q</span>(quit)
<span>head</span>	Display the beginning of a file	<span>head -n 20 file.log</span>
<span>tail</span>	Display the end of a file	<span>tail -f app.log</span> ⭐ Real-time log tracking
<span>vim</span>	Text editor	<span>i</span>(insert mode) <span>:wq</span>(save and exit) <span>:q!</span>(force quit)
<span>nano</span>	Simple editor	<span>Ctrl+O</span>(save) <span>Ctrl+X</span>(exit)

3. Permissions and User Management

Command	Function	Key Notes
<span>chmod</span>	Change permissions	<span>chmod 755 script.sh</span> (rwxr-xr-x)
<span>chown</span>	Change owner	<span>chown user:group file</span>
<span>sudo</span>	Execute with elevated privileges	<span>sudo apt update</span> ⭐ Temporarily gain root privileges
<span>passwd</span>	Change password	<span>passwd</span> (current user) <span>passwd username</span> (admin)
<span>useradd</span>	Add user	<span>useradd -m -s /bin/bash alice</span>
<span>usermod</span>	Modify user	<span>usermod -aG sudo bob</span> ⭐ Add sudo privileges

4. System Monitoring and Process Management

Command	Function	Useful Parameters
<span>top</span>	Dynamic process monitoring	<span>P</span>(sort by CPU) <span>M</span>(sort by memory)
<span>htop</span>	Enhanced version of top	⭐ Visual operation (requires installation)
<span>ps</span>	Process snapshot	`ps aux	grep nginx`
<span>kill</span>	Terminate process	<span>kill -9 PID</span> ⚠️ Force termination
<span>df</span>	Disk space	<span>df -h</span> (human-readable format)
<span>free</span>	Memory usage	<span>free -m</span> (in MB)

5. Network Tools

Command	Function	Classic Usage
<span>ping</span>	Network connectivity	<span>ping -c 4 google.com</span>
<span>ifconfig</span>/<span>ip</span>	Network configuration	<span>ip addr show</span>
<span>netstat</span>/<span>ss</span>	Network connections	<span>ss -tunlp</span> ⭐ View port usage
<span>curl</span>	Network request	<span>curl -I https://baidu.com</span> (only headers)
<span>wget</span>	File download	<span>wget -c url</span> ⚡ Resume download
<span>scp</span>	Secure copy	<span>scp file user@remote:/path</span>

6. Package Management

System	Command	Function
Debian/Ubuntu	<span>apt update</span>	Update source list
<span>apt install nginx</span>	Install software
<span>apt remove --purge pkg</span>	Completely uninstall
CentOS/RHEL	<span>yum install httpd</span>	Install software
<span>dnf groupinstall "Development Tools"</span>	Install development suite

7. Compression and Decompression

Format	Compression Command	Decompression Command
.tar	<span>tar -cvf archive.tar dir/</span>	<span>tar -xvf archive.tar</span>
.gz	<span>gzip file</span>	<span>gunzip file.gz</span>
.tar.gz	<span>tar -zcvf archive.tar.gz dir/</span>	<span>tar -zxvf archive.tar.gz</span>
.zip	<span>zip -r archive.zip dir/</span>	<span>unzip archive.zip</span>

8. Shell Tricks

Command	Function	Example
`	`	Pipe	`cat log.txt	grep “error”`
<span>></span>	Redirect output	<span>ls > files.txt</span> ⚠️ Overwrite file
<span>>></span>	Append output	<span>echo "new" >> file.txt</span>
<span>&&</span>	Command chaining	<span>make && make install</span>
<span>alias</span>	Create alias	<span>alias ll='ls -alh'</span> ⭐ To make permanent, write to <span>~/.bashrc</span>

9. Scheduled Tasks

Command	Function	Example
<span>crontab -e</span>	Edit scheduled tasks	<span>* * * * * /path/script.sh</span>
<span>crontab -l</span>	View task list	–
<span>at</span>	One-time scheduled task	`echo “cmd”	at 02:00`

10. System Information

Command	Function	Example Output
<span>uname -a</span>	System information	<span>Linux server 5.15.0-xx-generic</span>
<span>lsb_release -a</span>	Distribution information	<span>Ubuntu 22.04 LTS</span>
<span>lscpu</span>	CPU information	Number of cores/architecture/frequency
<span>lshw</span>	Hardware overview	⚡ Requires root privileges

📌 Pitfall Tips:

1. <span>rm -rf /</span> willdestroy the system! Always confirm the path before deleting

2. <span>chmod 777</span> lowers security; it is recommended to follow the principle of least privilege

3. Use <span>sudo</span> with caution in production environments to avoid accidental operations