Linux Cheatsheet

Commands below assume a modern systemd-based distro (Ubuntu, Debian, Fedora, Arch) with GNU coreutils. Package-manager sections are split by distro family.

Files and directories

ls -la

Lists all files, including hidden dotfiles, in long format with permissions and sizes.

cd -

Jumps back to the previous working directory.

pwd

Prints the current working directory’s full path.

mkdir -p a/b/c

Creates nested directories in one shot, without erroring if they already exist.

cp -r src/ dest/

Copies a directory recursively.

mv old.txt new.txt

Renames or moves a file (same command for both).

rm -rf build/

Deletes a directory and its contents without confirmation. Double-check the path first.

find . -name "*.log" -mtime -7

Finds files named *.log under the current directory modified in the last 7 days.

find . -type f -size +100M

Finds regular files larger than 100 MB.

locate nginx.conf

Searches a prebuilt filename index (fast, but needs sudo updatedb to stay current).

tree -L 2

Shows a directory tree two levels deep (install via apt install tree if missing).

ln -s /path/to/target linkname

Creates a symbolic link.

Viewing and editing files

cat file.txt

Prints a file’s contents to standard output.

less file.txt

Pages through a file; /pattern to search, q to quit.

head -n 20 file.txt

Prints the first 20 lines.

tail -n 20 file.txt

Prints the last 20 lines.

tail -f app.log

Follows a growing log file live; Ctrl+C to stop.

wc -l file.txt

Counts lines in a file (-w for words, -c for bytes).

diff -u old.txt new.txt

Shows a unified diff between two files.

nano file.txt

Opens a beginner-friendly terminal editor (Ctrl+O save, Ctrl+X exit).

Permissions and ownership

chmod 755 script.sh

Sets rwx for owner, rx for group and others (common for executables).

chmod +x script.sh

Adds execute permission without touching the rest of the mode bits.

chown user:group file.txt

Changes both owner and group.

chown -R user:group dir/

Applies ownership recursively to a directory tree.

umask 022

Sets the default permission mask for newly created files in this shell session.

stat file.txt

Shows detailed metadata: size, permissions, timestamps, inode.

Text processing

grep -rn "TODO" src/

Recursively searches for a pattern, printing matching line numbers.

grep -i "error" app.log

Case-insensitive search.

grep -v "DEBUG" app.log

Prints only lines that do NOT match the pattern.

sed -i 's/foo/bar/g' file.txt

In-place, global find-and-replace (GNU sed edits in place with no argument after -i; BSD/macOS needs -i '').

awk '{print $1, $3}' file.txt

Prints the 1st and 3rd whitespace-separated columns of each line.

sort file.txt | uniq -c

Sorts lines, then counts consecutive duplicates.

cut -d',' -f2 data.csv

Extracts the 2nd comma-delimited field from each line.

tr 'a-z' 'A-Z' < file.txt

Translates lowercase to uppercase, reading from a file via stdin redirection.

xargs -I{} echo "found: {}"

Runs a command once per line of input, substituting {} with each line - handy piped from find.

Processes and jobs

ps aux

Lists every running process with user, PID, CPU and memory usage.

top

Live, sortable view of process resource usage; q to quit.

htop

A friendlier, color top replacement (install via your package manager).

kill -9 1234

Force-kills the process with PID 1234. Prefer plain kill 1234 (SIGTERM) first.

killall firefox

Kills every process matching a name.

jobs

Lists jobs running in the current shell session.

command &

Runs a command in the background; combine with bg/fg to move it between foreground and background.

nohup ./long_task.sh &

Runs a command immune to hangups, so it survives you closing the terminal.

nice -n 10 ./cpu_heavy.sh

Runs a command with lower scheduling priority (higher niceness = lower priority).

Disk and filesystem

df -h

Shows disk space usage per mounted filesystem, human-readable.

du -sh dir/

Shows the total size of a directory, human-readable.

du -h --max-depth=1 . | sort -rh

Lists immediate subdirectory sizes, largest first.

lsblk

Lists block devices (disks and partitions) as a tree.

mount | grep /dev/sda1

Shows where a device is currently mounted.

tar -czvf archive.tar.gz dir/

Creates a gzip-compressed tarball.

tar -xzvf archive.tar.gz

Extracts a gzip-compressed tarball.

unzip archive.zip -d dest/

Extracts a zip archive into a target directory.

Package management

sudo apt update && sudo apt upgrade

Debian/Ubuntu: refreshes the package index, then upgrades installed packages.

sudo apt install htop

Debian/Ubuntu: installs a package.

sudo apt remove htop

Debian/Ubuntu: uninstalls a package, keeping its config files.

dpkg -l | grep nginx

Debian/Ubuntu: lists installed packages matching a name.

sudo dnf install htop

Fedora/RHEL: installs a package (older systems use yum with the same syntax).

sudo pacman -S htop

Arch: installs a package.

snap install code --classic

Installs a sandboxed Snap package (distro-agnostic where Snap is set up).

Networking

ip addr show

Lists network interfaces and their IP addresses (modern replacement for ifconfig).

ping -c 4 example.com

Sends 4 ICMP echo requests and stops.

curl -I https://example.com

Fetches only the response headers.

wget https://example.com/file.zip

Downloads a file over HTTP(S)/FTP.

ss -tulpn

Lists listening TCP/UDP sockets with the owning process (modern replacement for netstat).

See networking.md and ssh.md for a deeper cross-OS networking and remote-access reference.

System info and services

uname -a

Prints kernel name, version, and architecture.

hostnamectl

Shows hostname and OS/kernel details (systemd systems).

systemctl status nginx

Shows whether a systemd service is running, and recent log lines.

sudo systemctl restart nginx

Restarts a systemd-managed service.

sudo systemctl enable nginx

Makes a service start automatically on boot.

journalctl -u nginx -f

Follows live logs for a specific systemd unit.

uptime

Shows how long the system has been running plus load averages.

free -h

Shows RAM and swap usage, human-readable.

Users and environment

whoami

Prints the current username.

id

Prints the current user’s UID, GID, and group memberships.

sudo -i

Opens a root login shell (use sparingly; prefer sudo <command>).

export PATH="$HOME/bin:$PATH"

Prepends a directory to the current shell’s PATH.

env

Lists all environment variables in the current shell.

alias ll="ls -la"

Defines a shell shortcut for the current session (add to ~/.bashrc to persist).

history | grep docker

Searches command history for previously run commands.