Linux Commands Cheat Sheet

The everyday Linux command set on one page: navigation, files, permissions, processes, networking, disk, and the pipes that glue them together.

Orientation

Command	What it does
`pwd`	Print working directory — where am I?
`ls -la`	List everything here, long form, including hidden files
`cd path` / `cd ~` / `cd -`	Change directory / go home / go back to previous
`man cmd` or `cmd --help`	The manual / quick help for any command
`which cmd`	Where does this command live?
`history`	What have I typed lately?

Command	What it does
`mkdir -p a/b/c`	Create nested directories in one go
`touch file`	Create an empty file (or update its timestamp)
`cp src dest` / `cp -r dir dest`	Copy a file / a directory tree
`mv old new`	Move — which is also how you rename
`rm file` / `rm -rf dir`	Delete a file / a whole tree — permanent, no trash can
`cat file`	Print a file's contents
`less file`	Page through a long file (`q` to quit, `/` to search)
`head -20 file` / `tail -20 file`	First / last 20 lines
`tail -f app.log`	Follow a log as it grows — the debugging classic
`ln -s target linkname`	Symbolic link

Command	What it does
`find . -name "*.md"`	Find files by name, recursively
`find . -type d -name "node_modules"`	Find directories by name
`grep -r "text" .`	Search file contents recursively
`grep -ri "text" .`	Same, case-insensitive
`grep -l "text" *.log`	Just list the files that match
`du -sh *`	Size of everything here, human-readable
`df -h`	Disk space across mounted filesystems

Permission string: -rwxr-xr-- = type, then owner / group / other triads of read, write, execute.

Command	What it does
`chmod +x script.sh`	Make executable
`chmod 644 file`	Owner read/write; everyone else read (normal file)
`chmod 755 script`	Owner all; others read + execute (normal script/directory)
`chmod 600 secrets`	Owner read/write; nobody else anything (keys, credentials)
`chown user:group file`	Change owner (usually needs `sudo`)
`sudo cmd`	Run one command with elevated rights — deliberately, not reflexively

Numeric key: r=4, w=2, x=1, summed per triad — so 754 = rwx r-x r--.

Command	What it does
`ps aux`	Every running process
`ps aux \| grep node`	Find a specific one
`top` (or `htop` if installed)	Live process/CPU/memory view
`kill PID`	Ask a process to stop
`kill -9 PID`	Force it to stop (last resort)
`cmd &`	Run in the background
`jobs` / `fg`	List background jobs / bring one forward

Command	What it does
`uptime`	How long it has been up, and load average
`sudo reboot`	Restart now (`sudo systemctl reboot` is the same thing)
`sudo shutdown -r +5 "msg"`	Restart in 5 minutes, warning logged-in users
`sudo shutdown -h now` / `sudo poweroff`	Power off now
`sudo shutdown -c`	Cancel a scheduled shutdown
`who`	Who else is logged in — check before rebooting a shared box
`systemctl status svc`	Is a service running, and why did it stop?
`sudo systemctl restart svc`	Restart one service instead of the whole machine
`sudo systemctl enable --now svc`	Start it and have it start on boot
`journalctl -u svc -n 50`	Last 50 log lines for a service
`journalctl -b -p err`	Errors from this boot only
`ls /var/run/reboot-required`	Debian/Ubuntu: does a pending update need a reboot?

Command	What it does
`ping host`	Is it reachable?
`curl -I https://example.com`	Fetch just the HTTP headers
`curl -O url` / `wget url`	Download a file
`ssh user@host`	Open a shell on another machine
`scp file user@host:/path`	Copy a file over SSH
`ip a`	This machine's network interfaces and addresses
`ss -tlnp`	What's listening on which port (run with `sudo` to see process names)

Pattern	What it does
`a \| b`	Output of `a` becomes input of `b`
`cmd > file`	Write output to file (replace)
`cmd >> file`	Append output to file
`cmd 2> errors.txt`	Capture error output separately
`cmd1 && cmd2`	Run `cmd2` only if `cmd1` succeeded
`sort \| uniq -c \| sort -rn`	Count occurrences, most frequent first
`wc -l`	Count lines

Worked example — the five most common words in a file:

tr ' ' '\n' < essay.txt | sort | uniq -c | sort -rn | head -5

Family	Update index	Install	Remove
Debian / Ubuntu	`sudo apt update`	`sudo apt install pkg`	`sudo apt remove pkg`
Fedora / RHEL	`sudo dnf check-update`	`sudo dnf install pkg`	`sudo dnf remove pkg`
Arch	`sudo pacman -Sy`	`sudo pacman -S pkg`	`sudo pacman -R pkg`
Alpine (containers)	`apk update`	`apk add pkg`	`apk del pkg`

Go deeper: every command here is taught hands-on in Linux Command Line Essentials. Save this page — it's built to be the tab you keep open.