🐧 Linux Command Line

Multilingual DevOps cheat sheet: Linux, Docker, Git, Kubernetes, Helm, Terraform, practical scenarios & templates.

Published

31 August 2025

Basic and advanced commands for navigation, files, processes, networking, monitoring, packages and automation. Suitable for DevOps workflows.

🔹 Basic commands

Command	Example	Description
`cat`		Show file content or concatenate several files
	`cat file.txt`	View file content
	`cat file1 file2`	Concatenate and output two files
	`cat file1 file2 > merged.txt`	Concatenate files and save to a new file
`cd`		Change the current working directory
	`cd /etc`	Go to absolute path `/etc`
	`cd ~`	Go to the home directory
	`cd ..`	Move one level up
	`cd -`	Return to the previous directory
`clear`		Clear the terminal screen
`cp`		Copy files and directories
	`cp file1.txt file2.txt`	Copy a file with a new name
	`cp -r dir1 dir2`	Recursively copy a directory
	`cp -i file.txt /tmp/`	Copy with confirmation before overwrite
`echo`		Print a string or environment variable
	`echo "Hello, World!"`	Print a simple string
	`echo $HOME`	Show the home directory path
	`echo -e "1\t2\n3"`	Interpret escape sequences ( )
`history`		Display command history
`id`		Show UID, GID and group memberships of the current user
`ls`		List files and directories
	`ls -l`	Long listing with permissions and owners
	`ls -a`	Show hidden files
	`ls -lh`	Human-readable sizes
`mkdir`		Create directories
	`mkdir folder`	Create a single directory
	`mkdir -p a/b/c`	Create nested directories
	`mkdir dir{1,2,3}`	Create several directories at once
`mv`		Move or rename files/directories
	`mv oldname.txt newname.txt`	Rename a file
	`mv file.txt /path/to/dir/`	Move a file to another directory
	`mv *.txt archive/`	Move all `.txt` files to the `archive` folder
`pwd`		Print the current working directory
	`pwd -P`	Show the physical path (no symlinks)
	`cd /tmp && pwd`	Show path after changing to `/tmp`
`rm`		Remove files or directories
	`rm file.txt`	Delete a file
	`rm -i file.txt`	Delete a file with confirmation
	`rm -r folder/`	Recursively delete a directory
	`rm -rf folder/`	Force delete without confirmation
`rmdir`		Remove an empty directory
	`rmdir emptydir`	Remove the `emptydir` directory
`touch`		Create empty files or update modification time
	`touch newfile.txt`	Create a new empty file if it doesn’t exist
	`touch a b c`	Create several files at once
	`touch -c file.txt`	Update time without creating a file if absent
`whereis`		Locate the binary, source and man pages of a command
	`whereis ls`	Find locations for `ls`
	`whereis bash`	Show paths for Bash binary and docs
	`whereis -b bash`	Search for the binary only
`which`		Show the path of the command executable
	`which python3`	Path to `python3`
	`which grep`	Path to `grep`
	`which --skip-alias ls`	Skip aliases while searching
`whoami`		Print the effective user name

🔸 Intermediate level

Command	Example	Description
`chmod`		Change file or directory permissions
	`chmod 755 file`	Set permissions with octal notation (e.g. 755)
	`chmod +x script.sh`	Add the execute bit to a script
	`chmod -R 644 dir/`	Recursively set permissions on a directory
`chown`		Change file owner and group
	`chown user file`	Change the owner of a file
	`chown user:group file`	Change owner and group
	`chown -R user:group dir/`	Recursively change owner and group
`curl`		Transfer data from/to a server (HTTP, HTTPS, etc.)
	`curl -I https://example.com`	Send a HEAD request (headers only)
	`curl -O https://example.com/file.txt`	Download a file and keep its name
	`curl -d "a=1&b=2" -X POST URL`	Send a POST request with form data
`df`		Report file system disk space usage
	`df -h`	Human-readable sizes
	`df /home`	Usage of a specific mount point
	`df -T`	Show file system types
`diff`		Compare files or directories
	`diff file1 file2`	Compare two files
	`diff -u old.c new.c`	Unified diff (patch-style)
	`diff -r dir1 dir2`	Recursive directory comparison
`du`		Estimate file and directory space usage
	`du -sh *`	Show size of items in the current directory
	`du -h file.txt`	Show size of a single file
	`du -sh --max-depth=1 /var`	Summarise sizes of top-level subdirs
`find`		Search for files/directories by name, size, time, etc.
	`find . -name "*.log"`	Find all `.log` files in the current directory
	`find / -type f -size +100M`	Find files larger than 100 MB
	`find . -mtime -1`	Files modified within the last day
`free`		Display the amount of free and used memory
	`free -h`	Human-readable memory units
	`free -m`	Show values in MB
	`watch -n 2 free -h`	Refresh output every 2 seconds
`grep`		Search text using patterns (regular expressions)
	`grep "error" logfile`	Find lines containing `error`
	`grep -r "error" /var/log`	Recursive search in a directory
	`grep -i "fail" file`	Case-insensitive search
`head`		Output the first lines of a file
	`head -n 10 file`	First 10 lines
	`head -n 20 file.txt`	First 20 lines
	`head -c 100 file`	First 100 bytes
`hostname`		Show or set the system’s host name
	`hostname newname`	Temporarily set the host name until reboot
	`hostname -I`	Show IP addresses
`kill`		Send signals to processes
	`kill -9 1234`	Force-kill a process by PID
	`kill -TERM 1234`	Terminate gracefully with SIGTERM
	`pkill -f python`	Kill processes matching a pattern
`ping`		Check network connectivity using ICMP echo requests
	`ping 8.8.8.8`	Ping an address
	`ping -c 4 ya.ru`	Send 4 packets
	`ping -i 2 1.1.1.1`	Set a 2-second interval
`ps`		Report process status
	`ps aux`	List all processes
	`ps -ef \| grep nginx`	Filter by name using `grep`
	`ps -u $USER`	Processes of the current user
`rsync`		Fast incremental file transfer
	`rsync -av src/ dst/`	Synchronise directories locally
	`rsync -avz user@host:/src /dst`	Sync with a remote host over SSH
	`rsync --delete src/ dst/`	Delete files in destination missing in source
`scp`		Secure copy (remote file copy program)
	`scp file user@host:/path`	Copy a file to a remote host
	`scp user@host:/file.txt .`	Copy a file from a remote host
	`scp -r dir user@host:/path`	Recursively copy a directory
`sort`		Sort lines of text
	`sort file.txt`	Alphabetical sort
	`sort -r file.txt`	Reverse order
	`sort -n numbers.txt`	Numeric sort
`tail`		Output the last part of files; follow changes
	`tail -f logfile.log`	Follow a log in real time
	`tail -n 20 file.txt`	Show the last 20 lines
	`tail -c 100 file.txt`	Show the last 100 bytes
`tar`		Create, list or extract tar archives
	`tar -czf archive.tgz dir/`	Create a compressed `.tgz` archive
	`tar -xzf archive.tgz`	Extract a `.tgz` archive
	`tar -tf archive.tgz`	List archive contents
`tee`		Read from stdin and write to stdout and files
	`echo "test" \| tee out.txt`	Write output to `out.txt` and display it
	`ls \| tee list.txt`	Save `ls` output to a file and display it
	`command \| tee -a log.txt`	Append output to the end of `log.txt`
`top`		Display Linux tasks (interactive process viewer)
	`top`	Start top
	`htop`	Alternative interactive viewer (htop)
	`top -o %MEM`	Sort by memory usage
`uptime`		Show how long the system has been running
	`uptime -p`	Formatted uptime
	`uptime -s`	System boot time
`wget`		Non-interactive network downloader
	`wget https://site.com/file.zip`	Download a file by URL
	`wget -c file.zip`	Resume an interrupted download
	`wget -O saved.txt URL`	Save with a different filename
`wc`		Print line, word, and byte counts for files
	`wc -l file`	Count lines
	`wc -w file`	Count words
	`wc -m file`	Count characters
`uniq`		Report or filter out repeated lines (adjacent duplicates)
	`uniq file.txt`	Remove adjacent duplicates
	`sort file \| uniq`	Remove duplicates after sort
	`sort file \| uniq -c`	Count occurrences of each line
`yes`		Output a string repeatedly until killed; useful for scripting
	`yes "y" \| command`	Always answer “y” to prompts
	`yes \| rm -i *`	Auto-confirm interactive deletions
	`yes no \| command`	Answer “no” to prompts

🔧 Advanced commands

Command	Example	Description
`at`		Schedule a one-off command to run at a given time
	`at now + 1 minute`	Run a command one minute from now
	`atq`	List pending jobs
	`atrm`	Remove a pending job
`awk`		Pattern-scanning and processing language
	`awk '{print $1}' file`	Print the first column
	`ps aux \| awk '$3 > 50'`	Filter processes by CPU usage
	`cat file.txt \| awk '{print $2}'`	Print the second field from each line
	`awk '/error/ {print $0}' logfile`	Print lines matching a pattern
`crontab`		Install, list, or remove per-user cron jobs
	`crontab -e`	Edit the current user’s crontab
	`crontab -l`	List cron jobs
	`crontab -r`	Remove the current user’s crontab
`cut`		Remove or select sections from each line of files
	`cut -d':' -f1 /etc/passwd`	Print usernames from `/etc/passwd`
	`echo "a:b:c" \| cut -d':' -f2`	Cut the second field using ‘:’ as delimiter
	`cut -c1-5 filename`	Select characters by position
`df`		Report file system disk space usage
	`df -h`	Human-readable sizes
	`df -T`	Show file system types
	`df /home`	Usage for the home directory
`env`		Run a command in a modified environment or print environment variables
	`env \| grep PATH`	Show PATH entries
	`env -i bash`	Start a clean shell with an empty environment
`export`		Set environment variables for the current shell/session
	`export VAR=value`	Set a variable for this shell
	`export PATH=$PATH:/new/path`	Append a directory to PATH
	`export -p`	List exported variables
`free`		Display memory usage
	`free -m`	Show in MB
	`free -h`	Human-readable units
	`free -s 5`	Sample every 5 seconds
`hostnamectl`		Query and change the system host name and related settings
	`hostnamectl status`	Show host name status
	`hostnamectl set-hostname newname`	Set a new static host name
`ifconfig` / `ip`		IP tools to view/manage interfaces and addresses
	`ifconfig`	Show network interfaces (legacy)
	`ip a`	Show addresses with `ip`
	`ip link set eth0 up`	Bring an interface up
`iostat`		Report CPU and I/O statistics
	`iostat -x 2`	Extended stats every 2 seconds
	`iostat -d 5 3`	Device statistics (5s interval, 3 reports)
`iptables`		Administration tool for IPv4 packet filtering and NAT
	`iptables -L`	List current rules
	`iptables -A INPUT -p tcp --dport 22 -j ACCEPT`	Allow incoming SSH on port 22
	`iptables -F`	Flush all rules
`journalctl`		Query the systemd journal
	`journalctl -xe`	Show recent errors with context
	`journalctl -u nginx.service`	Show logs for a service
	`journalctl --since "2 hours ago"`	Show logs since a relative time
`ln`		Make links between files
	`ln -s target link`	Create a symbolic link
	`ln file.txt backup.txt`	Create a hard link
	`ln -sf target link`	Force recreate a symbolic link
`sed`		Stream editor for filtering and transforming text
	`sed 's/old/new/g' file`	Replace a string globally
	`sed -n '1,5p' file`	Print only a range of lines
	`sed '/pattern/d' file`	Delete matching lines
`systemctl`		Control the systemd system and service manager
	`systemctl status nginx`	Show service status
	`systemctl start nginx`	Start a service
	`systemctl enable nginx`	Enable a service at boot
`tr`		Translate or delete characters
	`tr a-z A-Z`	Convert lowercase to uppercase
	`echo "hello" \| tr 'h' 'H'`	Replace a character
	`echo "abc123" \| tr -d '0-9'`	Delete digits
`type`		Describe how a name would be interpreted in the shell
	`type ls`	Show how `ls` is resolved
	`type cd`	Show how `cd` is resolved
	`type python3`	Show how `python3` is resolved
`ulimit`		Get or set user process resource limits
	`ulimit -n`	Show max open files
	`ulimit -c unlimited`	Enable core dumps
	`ulimit -u 4096`	Limit the number of user processes
`uptime`		Show system uptime and average load
	`uptime -p`	Formatted uptime
	`uptime -s`	Show boot time
`xargs`		Build and execute command lines from standard input
	`xargs -n 1 echo`	Echo each argument on a separate line
	`echo "a b c" \| xargs -n 1`	Split words into separate arguments
	`find . -name '*.txt' \| xargs rm`	Find files and remove them with xargs

🌐 Network commands

Command	Example	Description
`curl`		Transfer data to/from servers
	`curl -X POST -d "a=1" URL`	POST request with form data
	`curl -I URL`	Fetch headers only
	`curl -o file.html URL`	Download and save to a file
`dig`		DNS lookup utility
	`dig openai.com`	Query A records
	`dig +short openai.com`	Short answer
	`dig @8.8.8.8 openai.com`	Use a specific DNS server
`ftp`		File Transfer Protocol client
	`ftp host`	Connect to an FTP server
	`ftp -n host`	Connect without auto-login
	`ftp> get file.txt`	Download a file in an FTP session
`ip address`		Show/manipulate IP addresses
	`ip addr show eth0`	Show address info for `eth0`
	`ip addr`	List all addresses
`ip link`		Show/manipulate network devices
	`ip link show`	Show network links
	`ip link set eth0 up`	Bring an interface up
`ip route`		Show/manipulate the IP routing table
	`ip route list`	List routing table
	`ip route add default via 192.168.1.1`	Add a default route
`nc`		Arbitrary TCP/UDP connections and listeners
	`nc -zv host 22`	Port scan a host
	`nc -l 1234`	Listen on a TCP port
	`nc host 1234 < file`	Send a file to a remote port
`nmap`		Network exploration tool and security/port scanner
	`nmap -sP 192.168.1.0/24`	Ping scan a subnet
	`nmap -sV 192.168.1.1`	Service/version detection
	`nmap -O 192.168.1.1`	OS detection
`nslookup`		Query Internet domain name servers
	`nslookup google.com`	Query a domain name
	`nslookup 8.8.8.8`	Reverse lookup for an IP
`ssh`		OpenSSH remote login client
	`ssh user@host`	Connect to a host
	`ssh -p 2222 user@host`	Connect using a non-default port
	`ssh -i ~/.ssh/id_rsa user@host`	Login with a specific private key
`ss`		Utility to investigate sockets
	`ss -tuln`	List TCP/UDP listening ports
	`ss -s`	Summary statistics
	`ss -l`	List listening sockets
`telnet`		User interface to the TELNET protocol
	`telnet host 80`	Connect to a host on port 80
	`telnet example.com 443`	Connect to 443
	`telnet localhost 25`	Connect to local SMTP
`traceroute`		Trace the route to a network host
	`traceroute 8.8.8.8`	Trace path to an IP
	`traceroute -m 15 8.8.8.8`	Limit max hops
`wget`		Retrieve files from the web
	`wget -O file.txt URL`	Save output to a file
	`wget URL`	Download to the current directory
	`wget -c URL`	Continue a partial download

🔍 Searching and managing files

Command	Example	Description
`basename`		Strip directory and suffix from file names
	`basename /path/to/file`	Print the file name from a path
	`basename /path/to/file .txt`	Strip a suffix from the name
`dirname`		Strip last component from a path
	`dirname /path/to/file`	Show directory part of the path
	`dirname /etc/passwd`	Show parent of `/etc/passwd`
`du`		Estimate file space usage
	`du -sh folder/`	Show size of a directory
	`du -h *`	Show size of items in the current directory
	`du -c folder1 folder2`	Cumulative size of multiple directories
`file`		Determine file type
	`file some.bin`	Detect file type
	`file *`	Detect types for all files in a directory
	`file -i file.txt`	Show MIME type
`find`		Search for files
	`find /path -type f -name "*.sh"`	Find shell scripts by name
	`find . -size +10M`	Find files larger than 10 MB
	`find /tmp -mtime -1`	Find files modified in the last day
`locate`		Find files by name using a database
	`locate filename`	Locate a file name
	`locate *.conf`	Wildcard search
	`locate -i README`	Case-insensitive search
`realpath`		Print the resolved absolute path
	`realpath file`	Resolve a file path
	`realpath ../relative/path`	Resolve a relative path
`stat`		Display file or file system status
	`stat file`	Show detailed file status
	`stat -c %s file`	Print file size only
	`stat -f file`	Show file system status
`tree`		List contents of directories in a tree-like format
	`tree`	Print directory tree
	`tree -L 2`	Limit the display depth
	`tree -a`	Include hidden files

📊 System monitoring

Command	Example	Description
`dmesg`		Print or control the kernel ring buffer
	`dmesg \| tail`	Show the last kernel messages
	`dmesg \| grep usb`	Filter for USB messages
`free`		Display memory usage
	`free -h`	Human-readable units
	`free -m`	Show in MB
`htop`		Interactive process viewer
	`htop`	Run `htop`
`iotop`		Display I/O usage by processes
	`iotop`	Run `iotop`
	`iotop -o`	Show only processes doing I/O
`lsof`		List open files
	`lsof -i :80`	Show processes using port 80
	`lsof -u username`	Show files open by a user
`uptime`		Show system uptime and load averages
`vmstat`		Report virtual memory statistics
	`vmstat 1`	Refresh every 1 second
	`vmstat 5 3`	Five-second interval, 3 reports
`watch`		Execute a programme periodically, showing output
	`watch -n 1 df -h`	Watch disk usage
	`watch -d free -h`	Highlight differences and watch memory

📦 Package management

Command	Example	Description
`apt`		APT package manager (Debian/Ubuntu)
	`apt install curl`	Install a package
	`apt remove curl`	Remove a package
	`apt update && apt upgrade`	Update package lists and upgrade
`dnf`		Dandified YUM (Fedora/RHEL family)
	`dnf install curl`	Install a package
	`dnf upgrade`	Upgrade packages
`rpm`		RPM package manager
	`rpm -ivh package.rpm`	Install an RPM package
	`rpm -e package`	Erase (uninstall) a package
`snap`		Snappy package manager
	`snap install app`	Install a snap
	`snap remove app`	Remove a snap
`yum`		Yellowdog Updater Modified (RHEL/CentOS)
	`yum install curl`	Install a package
	`yum remove curl`	Remove a package

💽 File systems

Command	Example	Description
`blkid`		Locate/print block device attributes
	`blkid`	List block devices and attributes
`df`		Report file system disk space usage
	`df -Th`	Human-readable sizes by type
`fsck`		Check and repair a Linux file system
	`fsck /dev/sda1`	Check a device
`lsblk`		List information about block devices
	`lsblk`	List devices in a tree
`mkfs`		Build a Linux file system
	`mkfs.ext4 /dev/sdb1`	Create an ext4 file system
`mount`		Mount a file system
	`mount /dev/sdb1 /mnt`	Mount a device to `/mnt`
	`mount \| grep /mnt`	Show mounted file systems filtered by path
`parted`		Partition manipulation programme
	`parted /dev/sdb`	Open a disk for partitioning
`umount`		Unmount file systems
	`umount /mnt`	Unmount a mount point

🤖 Scripts and automation

Command	Example	Description
`alias`		Define or display shell aliases
	`alias ll='ls -la'`	Create a handy alias
	`alias`	List defined aliases
`bash` / `sh`		Run shell scripts
	`bash script.sh`	Run a script with Bash
	`sh script.sh`	Run a script with `sh`
`crontab`		Per-user cron tables
	`crontab -e`	Edit the current user’s crontab
`read`		Prompt for user input in shell scripts
	`read name`	Read into a variable
`set`		Set shell options/positional parameters
	`set -e`	Exit on first error
`source`		Read and execute commands from a file in the current shell
	`source ~/.bashrc`	Reload shell configuration
`trap`		Trap signals and execute commands
	`trap "echo 'exit'" EXIT`	Run a command on shell exit

🛠 Development and debugging

Command	Example	Description
`gcc`		GNU C compiler
	`gcc main.c -o app`	Compile a C source file
`gdb`		GNU debugger
	`gdb ./app`	Debug a compiled binary
`git`		Distributed version control system
	`git status`	Show status of the working tree
	`git commit -m "msg"`	Commit with a message
`ltrace`		Library call tracer
	`ltrace ./app`	Trace library calls of a binary
`make`		Utility to maintain groups of programmes
	`make`	Build according to Makefile
`shellcheck`		Static analysis for shell scripts
	`shellcheck script.sh`	Lint a shell script
`strace`		Trace system calls and signals
	`strace ./app`	Trace a programme’s syscalls
`valgrind`		Instrumentation framework for building dynamic analysis tools
	`valgrind ./app`	Run a programme under Valgrind
`vim` / `nano`		Command-line text editors
	`vim file.sh`	Edit with Vim
	`nano file.sh`	Edit with Nano

📌 Miscellaneous

Command	Example	Description
`cal`		Display a calendar
	`cal 2025`	Show a year calendar
	`cal 08 2025`	Show a specific month
`date`		Display or set the system date and time
	`date +%T`	Print current time (HH:MM:SS)
	`date -d "next friday"`	Print date for a relative day
`factor`		Factor integers
	`factor 100`	Factorise a number
`man`		Format and display the manual pages
	`man tar`	Open a man page
	`man -k copy`	Search manuals by keyword
	`man 5 passwd`	Open a specific manual section
`seq`		Print sequences of numbers
	`seq 1 5`	Count from 1 to 5
	`seq 1 2 9`	Count with step
	`seq -s ',' 1 5`	Join numbers with a custom separator
`yes`		Output a string repeatedly until killed
	`yes \| rm -r dir`	Auto-confirm a recursive removal

📚 Additional resources

📘 man pages – detailed manuals for commands:

man ls
man rm

📙 TLDR – concise usage examples of popular commands:

🧠 Tip: Install tldr for cheat-sheet-style help:

sudo apt install tldr   # or: npm install -g tldr
tldr tar                # example of a short summary for the tar command

🌐 Useful links

Linux man pages online — official manual pages, searchable by command name:
https://man7.org/linux/man-pages/

Simplified and community-driven man pages — community help pages with practical examples:
https://tldr.sh/