100 Essential High-Frequency Linux Commands for Reference

2025-09-20

The following is a complete reference manual for 100 high-frequency Linux commands, categorized with command names, function descriptions, common parameters, and typical use cases:

1. File and Directory Operations (15 commands)

Command	Function Description	Parameter Examples	Typical Use Case
`<span><span>ls</span></span>`	List directory contents	`<span><span>-l for detailed information </span></span><code><span><span>-a</span></span>`Show hidden files	`<span><span>ls -la /etc</span></span>`
`<span><span>cd</span></span>`	Change directory	`<span><span>~ user directory </span></span><code><span><span>-</span></span>`Return to the last directory	`<span><span>cd /var/log</span></span>`
`<span><span>pwd</span></span>`	Display current path	None	Get working directory in scripts
`<span><span>mkdir</span></span>`	Create directory	`<span><span>-p create recursively</span></span>`	`<span><span>mkdir -p project/{src,test}</span></span>`
`<span><span>rm</span></span>`	Delete file	`<span><span>-rf force recursive delete</span></span>`	`<span><span>rm -rf tmp/</span></span>`
`<span><span>cp</span></span>`	Copy file	`<span><span>-a preserve all attributes</span></span>`	`<span><span>cp -a dir1 dir2</span></span>`
`<span><span>mv</span></span>`	Move/Rename	None	`<span><span>mv old.txt new.txt</span></span>`
`<span><span>touch</span></span>`	Create empty file	None	`<span><span>touch lock.file</span></span>`
`<span><span>file</span></span>`	Detect file type	None	`<span><span>file /bin/bash</span></span>`
`<span><span>ln</span></span>`	Create link	`<span><span>-s symbolic link</span></span>`	`<span><span>ln -s /data/logs logs</span></span>`
`<span><span>chmod</span></span>`	Change permissions	`<span><span>755/</span></span><code><span><span>644</span></span>`	`<span><span>chmod +x script.sh</span></span>`
`<span><span>chown</span></span>`	Change owner	`<span><span>user:group</span></span>`	`<span><span>chown www:www /var/www</span></span>`
`<span><span>find</span></span>`	File search	`<span><span>-name by name </span></span><code><span><span>-type</span></span>` by type	`<span><span>find / -name "*.conf"</span></span>`
`<span><span>locate</span></span>`	Quick search	`<span><span>-i ignore case</span></span>`	`<span><span>locate nginx.conf</span></span>`
`<span><span>du</span></span>`	Statistics size	`<span><span>-sh summary display</span></span>`	`<span><span>du -sh /home/*</span></span>`

2. Text Processing (12 commands)

Command	Function Description	Parameter Examples	Typical Use Case
`<span><span>cat</span></span>`	View file	`<span><span>-n show line numbers</span></span>`	`<span><span>cat -n server.log</span></span>`
`<span><span>less</span></span>`	Paginated view	`<span><span>+F real-time tracking</span></span>`	`<span><span>less +F debug.log</span></span>`
`<span><span>head</span></span>`	Display head	`<span><span>-n 10 first 10 lines</span></span>`	`<span><span>head -n 5 access.log</span></span>`
`<span><span>tail</span></span>`	Display tail	`<span><span>-f real-time tracking</span></span>`	`<span><span>tail -f app.log</span></span>`
`<span><span>grep</span></span>`	Text search	`<span><span>-i </span></span><span><span>ignore case </span></span><code><span><span>-v</span></span>` reverse match	`<span><span>grep -i "error" *.log</span></span>`
`<span><span>awk</span></span>`	Text analysis	`<span><span>{print $1} first column</span></span>`	`<span><span>awk '{print $4,$7}' log</span></span>`
`<span><span>sed</span></span>`	Stream editor	`<span><span>s/old/new/g replace</span></span>`	`<span><span>sed 's/foo/bar/g' file</span></span>`
`<span><span>sort</span></span>`	Sort	`<span><span>-n </span></span><span><span>numeric sort -r</span></span><span><span> reverse order</span></span>`	`<span><span>sort -nr data.txt</span></span>`
`<span><span>uniq</span></span>`	Remove duplicates	`<span><span>-c count</span></span>`	sort file
`<span><span>wc</span></span>`	Statistics	`<span><span>-l </span></span><span><span>line count</span></span>` `<span><span>-w</span></span>` word count	`<span><span>wc -l report.txt</span></span>`
`<span><span>cut</span></span>`	Extract by column	`<span><span>-d':' -f1 first column</span></span>`	`<span><span>cut -d' ' -f1 log</span></span>`
`<span><span>tr</span></span>`	Character replacement	`<span><span>'a-z' 'A-Z' to uppercase</span></span>`	echo “hello” \| tr ‘a-z’ ‘A-Z’

3. System Monitoring (10 commands)

Command	Monitoring Metrics	Key Parameters	Typical Output
`<span><span>top</span></span>`	Real-time processes	`<span><span>1 CPU details</span></span>`	`<span><span>PID USER %CPU %MEM COMMAND</span></span>`
`<span><span>htop</span></span>`	Enhanced monitoring	`<span><span>-u user filter</span></span>`	Colored process list
`<span><span>free</span></span>`	Memory	`<span><span>-h human-readable</span></span>`	`<span><span>total used free shared buff/cache</span></span>`
`<span><span>vmstat</span></span>`	System load	`<span><span>2 5 refresh every 2 seconds</span></span>`	`<span><span>r run queue length</span></span>`
`<span><span>iostat</span></span>`	Disk IO	`<span><span>-x detailed statistics</span></span>`	`<span><span>%util disk utilization</span></span>`
`<span><span>sar</span></span>`	Historical data	`<span><span>-u </span></span><span><span>CPU -r</span></span><span><span> memory</span></span>`	Generate trend reports
`<span><span>dmesg</span></span>`	Kernel log	`<span><span>-T show time</span></span>`	Hardware error diagnosis
`<span><span>journalctl</span></span>`	System log	`<span><span>-u </span></span><span><span>service name</span></span>` —`<span><span>since</span></span>` time range	`<span><span>journalctl -u nginx</span></span>`
`<span><span>lsof</span></span>`	Open files	`<span><span>-i:80 port usage</span></span>`	View files used by processes
`<span><span>netstat</span></span>`	Network connections	`<span><span>-tulnp listening ports</span></span>`	`<span><span>Proto Recv-Q Send-Q Local Address</span></span>`

4. Network Management (12 commands)

Command	Function Description	Protocol Support	Typical Use Case
`<span><span>ifconfig</span></span>`	Network interface	IPv4/IPv6	`<span><span>ifconfig eth0</span></span>`
`<span><span>ip</span></span>`	Modern network tool	All protocols	`<span><span>ip addr show</span></span>`
`<span><span>ping</span></span>`	Connectivity test	ICMP	`<span><span>ping -c 4 google.com</span></span>`
`<span><span>traceroute</span></span>`	Route tracing	ICMP/UDP	`<span><span>traceroute 8.8.8.8</span></span>`
`<span><span>ss</span></span>`	Socket statistics	TCP/UDP	`<span><span>ss -tulnp</span></span>`
`<span><span>dig</span></span>`	DNS query	DNS	`<span><span>dig +short example.com</span></span>`
`<span><span>nslookup</span></span>`	Domain resolution	DNS	`<span><span>nslookup google.com</span></span>`
`<span><span>curl</span></span>`	Network request	HTTP/FTP etc.	`<span><span>curl -I https://example.com</span></span>`
`<span><span>wget</span></span>`	File download	HTTP/FTP	`<span><span>wget -c https://example.com/file.iso</span></span>`
`<span><span>ssh</span></span>`	Remote connection	SSH	`<span><span>ssh -p 2222 user@host</span></span>`
`<span><span>scp</span></span>`	Secure transfer	SSH	`<span><span>scp file.txt user@host:/path</span></span>`
`<span><span>rsync</span></span>`	Sync backup	SSH/local	`<span><span>rsync -avz src/ dest/</span></span>`

5. Permissions and Users (8 commands)

Command	Function	Key Parameters	Example
`<span><span>useradd</span></span>`	Add user	`<span><span>-m </span></span><span><span>Create directory</span></span>` `<span><span>-s</span></span>` specify shell	`<span><span>useradd -m -s /bin/bash bob</span></span>`
`<span><span>passwd</span></span>`	Change password	None	`<span><span>passwd alice</span></span>`
`<span><span>usermod</span></span>`	Modify user	`<span><span>-aG append group</span></span>`	`<span><span>usermod -aG sudo bob</span></span>`
`<span><span>userdel</span></span>`	Delete user	`<span><span>-r delete directory</span></span>`	`<span><span>userdel -r tempuser</span></span>`
`<span><span>groupadd</span></span>`	Add group	None	`<span><span>groupadd devs</span></span>`
`<span><span>chage</span></span>`	Password policy	`<span><span>-l </span></span><span><span> view</span></span>`-M 90 validity period	`<span><span>chage -l bob</span></span>`
`<span><span>sudo</span></span>`	Execute with elevated privileges	`<span><span>-u specify user</span></span>`	`<span><span>sudo -u www cat /var/www/config</span></span>`
`<span><span>vi sudo</span></span>`	Edit sudo configuration	None	Securely modify permissions

6. Package Management (10 commands)

System Type	Install Command	Upgrade Command	Cleanup Command
Debian/Ubuntu	`<span><span>apt install pkg</span></span>`	`<span><span>apt update && apt upgrade</span></span>`	`<span><span>apt autoremove</span></span>`
RHEL/CentOS	`<span><span>yum install pkg</span></span>`	`<span><span>yum update</span></span>`	`<span><span>yum clean all</span></span>`
Fedora	`<span><span>dnf install pkg</span></span>`	`<span><span>dnf upgrade</span></span>`	`<span><span>dnf clean all</span></span>`
Arch	`<span><span>pacman -S pkg</span></span>`	`<span><span>pacman -Syu</span></span>`	`<span><span>pacman -Rns $(pacman -Qdtq)</span></span>`
Generic	`<span><span>snap install pkg</span></span>`	`<span><span>snap refresh</span></span>`	`<span><span>snap remove pkg</span></span>`
Python	`<span><span>pip install pkg</span></span>`	`<span><span>pip install --upgrade pkg</span></span>`	`<span><span>pip uninstall pkg</span></span>`
Source Installation	`<span><span>./configure;make;make install</span></span>`	None	`<span><span>make uninstall</span></span>`
RPM Package	`<span><span>rpm -ivh pkg.rpm</span></span>`	`<span><span>rpm -Uvh pkg.rpm</span></span>`	`<span><span>rpm -e pkg</span></span>`
DEB Package	`<span><span>dpkg -i pkg.deb</span></span>`	`<span><span>dpkg -i pkg.deb</span></span>`	`<span><span>dpkg -r pkg</span></span>`
Flatpak	`<span><span>flatpak install pkg</span></span>`	`<span><span>flatpak update</span></span>`	`<span><span>flatpak uninstall pkg</span></span>`

7. Process Management (8 commands)

Command	Function	Signal/Parameter	Example
`<span><span>ps</span></span>`	Process snapshot	`<span><span>aux </span></span><span><span>all processes </span></span><code><span><span>-ef</span></span>` full format	ps aux
`<span><span>kill</span></span>`	Terminate process	`<span><span>-9</span></span><span><span> force terminate -15</span></span><span><span> graceful terminate</span></span>`	`<span><span>kill -9 1234</span></span>`
`<span><span>pkill</span></span>`	Terminate by name	`<span><span>-f match full command</span></span>`	`<span><span>pkill -f "python script.py"</span></span>`
`<span><span>killall</span></span>`	Terminate same name processes	`<span><span>-I ignore case</span></span>`	`<span><span>killall -I chrome</span></span>`
`<span><span>nohup</span></span>`	Run persistently	Output redirection	`<span><span>nohup ./start.sh &</span></span>`
`<span><span>bg/fg</span></span>`	Background/Foreground	None	`<span><span>bg %1 and fg %2</span></span>`
`<span><span>jobs</span></span>`	View background	`<span><span>-l show PID</span></span>`	Manage multitasking
`<span><span>nice</span></span>`	Adjust priority	`<span><span>-n priority value</span></span>`	`<span><span>nice -n 10 ./task.sh</span></span>`

8. Disk Management (10 commands)

Command	Function	Key Parameters	Example Output
`<span><span>df</span></span>`	Disk space	`<span><span>-hT </span></span><span><span>human-readable</span></span>`+FS type	`<span><span>Filesystem Size Used Avail Use% Mounted on</span></span>`
`<span><span>fdisk</span></span>`	Partition tool	`<span><span>-l list partitions</span></span>`	`<span><span>/dev/sda1 * 2048 2099199 1G 83 Linux</span></span>`
`<span><span>parted</span></span>`	Advanced partitioning	`<span><span>print all show all</span></span>`	Supports GPT partition table
`<span><span>mkfs</span></span>`	Create FS	`<span><span>-t ext4 specify type</span></span>`	`<span><span>mkfs -t xfs /dev/sdb1</span></span>`
`<span><span>fsck</span></span>`	File system check	`<span><span>-y auto repair</span></span>`	Repair damaged partition
`<span><span>mount</span></span>`	Mount device	`<span><span>-o mount options</span></span>`	`<span><span>mount /dev/sdb1 /data</span></span>`
`<span><span>umount</span></span>`	Unmount device	`<span><span>-l force unmount</span></span>`	Safely remove storage
`<span><span>lsblk</span></span>`	Block devices	`<span><span>-f show FS</span></span>`	`<span><span>NAME FSTYPE LABEL UUID MOUNTPOINT</span></span>`
`<span><span>blkid</span></span>`	Device UUID	None	Get unique identifier
`<span><span>badblocks</span></span>`	Bad block detection	`<span><span>-v detailed information</span></span>`	Check disk health status

9. Log Analysis (8 commands)

Command Combination	Function	Pipeline Techniques	Example
`<span><span>grep + awk</span></span>`	Extract key fields	grep “404”	awk ‘{print $7}’`
`<span><span>sort + uniq</span></span>`	Count frequency	sort	uniq -c
`<span><span>tail + grep</span></span>`	Real-time filtering	tail -f log	grep -v DEBUG
`<span><span>cut + sort</span></span>`	Column analysis	cut -d’ ‘ -f1	sort
`<span><span>journalctl + grep</span></span>`	System log analysis	journalctl –since “1 hour ago”	grep fail
`<span><span>sed + awk</span></span>`	Complex transformation	awk -F, ‘NF>=3 {print $2 ” \| ” $3}’ data.csv \| sed ‘/^$/d’
`<span><span>find + xargs</span></span>`	Batch processing	find . -name “*.log”	xargs rm
`<span><span>column -t</span></span>`	Align output	ls -l	column -t

10. Security Related (7 commands)

Tool	Detection Type	Key Parameters	Typical Usage
`<span><span>nmap</span></span>`	Port scanning	`<span><span>-sV </span></span><span><span>Service identification </span></span><code><span><span>-O</span></span>` OS detection	`<span><span>nmap -sS -p 1-1024 192.168.1.1</span></span>`
`<span><span>fail2ban</span></span>`	Prevent brute force	`<span><span>-status view status</span></span>`	Protect SSH service
`<span><span>chroot</span></span>`	Isolated environment	None	Create a restricted file system
`<span><span>openssl</span></span>`	Encryption tool	`<span><span>s_client</span></span><span><span> test connection</span></span>`req generate certificate	`<span><span>openssl s_client -connect example.com:443</span></span>`
`<span><span>iptables</span></span>`	Firewall	`<span><span>-A INPUT -p tcp --dport 80 -j ACCEPT</span></span>`	Configure access rules
`<span><span>auditd</span></span>`	Audit system	`<span><span>-l view rules</span></span>`	Monitor access to sensitive files
`<span><span>sestatus</span></span>`	SELinux status	None	Check mandatory access control

A total of 100 commands, covering all scenarios of Linux system management. Recommendations:

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