The Complete Linux Commands Cheat Sheet 2026

Navigating and managing a server or development environment via CLI is a foundational step for DevOps engineers, software developers, and system administrators. This reference acts as an index of the operations you will perform daily on Unix-like operating systems.

1. Navigation & Directory Operations

pwd: Prints the absolute path of the current working directory.

pwd

ls: Lists directory contents. Common flags include -l (long list details), -a (show hidden files), and -h (human-readable file sizes).

# List files in detailed format (including hidden files)
ls -lah

# List files sorted by last modified time (newest first)
ls -lt

cd: Changes directory. Navigates to a specific folder path.

# Go to home directory
cd ~

# Move up one directory level
cd ..

# Go to a specific folder
cd /var/log

mkdir: Creates a new directory. Write -p to recursively create nested parent directories.

# Create a folder
mkdir project

# Create nested folders recursively
mkdir -p project/src/components

rmdir: Removes empty directories.

rmdir empty_matching_folder

rm: Deletes files or directories. Use -r for recursion and -f to force delete without confirm.

# Delete a single file
rm temp.txt

# Recursively delete a directory and its contents
rm -rf obsolete_project

cp: Copies files or directories.

# Copy file to another location
cp config.json config.backup.json

# Copy directory containing items recursive
cp -r src/ public/

mv: Moves or renames files or folders.

# Rename a file
mv oldname.txt newname.txt

# Move file into a specific directory folder
mv data.csv ./database/

touch: Creates an empty file or updates the access/modification timestamps of an existing file.

touch index.js

2. File Viewing & Permissions

cat: Concatenates and displays file contents in the stdout output.

cat package.json

less: Displays files with paginated navigation, allowing forward and backward scrolling.

less system.log

head / tail: Shows the beginning or end of file lines. Use -n for line limits and -f to view logs in real time.

# Output the first 15 lines of a file
head -n 15 main.go

# Output the tailing 10 lines of a file
tail -n 10 server.log

# Stream and follow additions to log files dynamically
tail -f access.log

chmod: Re-configures read (4), write (2), and execute (1) access rights for Owner, Group, and Public users.

# Set executable permissions for the file group owner
chmod +x deploy.sh

# Restrict file: Read/Write for owner only (4+2=6, group/others=0)
chmod 600 private.key

# Set public Read-Only: read/write/execute for owner, read-only for others
chmod 744 run.py

chown: Modifies user owner and group affiliations of files and directories.

# Change owner to username
chown admin app.log

# Change owner and group simultaneously
chown admin:editors app.log

3. Text Processing & Searching

grep: Searches for pattern lines matching strings or regular expression filters.

# Search for "error" in a file (case-insensitive)
grep -i "error" server.log

# Recursively search for matching content lines in directory files
grep -rn "TODO" ./src

find: Scans the directory hierarchy for files matching criteria (name, type, size, modification).

# Find files ending in ".js" under directory
find . -name "*.js"

# Find directories matching name pattern
find /var -type d -name "log*"

# Find files modified within last 24 hours
find . -type f -mtime -1

awk: Stream processing language designed for column extraction and reporting.

# Extract and print second column of CSV/spaced output
awk '{print $2}' logs.txt

sed: Stream editor for performing pattern substitutions and mutations inline or in stream.

# Replace the first occurrence of "localhost" with "127.0.0.1" in config file
sed -i 's/localhost/127.0.0.1/' env.conf

xargs: Passes stdout streams as argument parameters to execution blocks.

# Find all .tmp files and delete them using xargs rm
find . -name "*.tmp" | xargs rm

4. System Monitoring & Information

top / htop: Dynamic views of current CPU execution threads, memory usages, and active running processes.

htop

df: Analyzes disk space allocations across active storage partitions.

# Detailed layout with human-readable space formatting
df -h

du: Evaluates storage space size consumed by folders and files.

# Summarise folder size usage footprint (human-readable)
du -sh ./node_modules

free: Reports system configuration memory slots (used, free, buffered, swap).

# Print memory metrics in megabytes
free -m

ps: Displays snapshot data describing currently active system processes.

# Find information for running node processes
ps aux | grep "node"

kill / killall: Terminate executing processes by assigning PID handles or process label strings.

# Terminate process using specific PID handler
kill 3422

# Force kill process
kill -9 3422

systemctl: Administers Linux services systemd daemon (start, stop, status, restart).

# Check system service running state
systemctl status nginx

# Restart background system daemon
sudo systemctl restart nginx

5. Network & Connectivity

ping: Tests TCP/IP packet connectivity state metrics to hosts.

ping google.com

curl: Fetches data or performs API calls over supported web protocols (HTTP/S, FTP).

# Fetch API endpoint data and output to terminal stdout
curl https://api.ipify.org

# Send POST request payload with Authorization headers
curl -X POST -H "Content-Type: application/json" -d '{"ready":true}' https://example.com/api

wget: Downloads packages and files from URLs recursively directly onto target paths.

wget https://releases.ubuntu.com/24.04/ubuntu-server.iso

ip: Display and configure network interface parameters, routing tables, and tunnels.

# View configuration attributes for active interfaces
ip addr show

ss / netstat: Outputs network socket connections metrics.

# View open listening TCP ports in detailed format
ss -ltnp

ssh: Secure Shell client connection utility to access remote server hosts.

ssh -i key.pem ubuntu@54.210.12.34

scp: Secure copy files between hosts over standard SSH tunnel protocols.

# Send local file destination parameters onto remote server path
scp -i key.pem file.zip ubuntu@54.210.12.34:/var/www

6. User & Privilege Management

sudo: Runs a terminal command with root supervisor admin credentials.

sudo apt update

whoami: Returns current active shell credentials username.

whoami

id: Prints user account ids (UID) and related group ids (GID).

id

passwd: Changes user account passwords.

passwd

7. Package Management

apt / dnf / yum: Native package manager suites to lookup, install, update, and drop binaries.

# Update local repository cache indexes (Ubuntu/Debian)
sudo apt update

# Install software suite dependency
sudo apt install build-essential

# Remove software and purge configuration schemas
sudo apt purge nginx

8. Archive & Compression

tar: Bundles file systems together. Common syntax incorporates -c (create), -x (extract), -z (gzip), -v (verbose), and -f (target file handler).

# Pack and compress folder structure files
tar -czvf distribution.tar.gz ./src

# Extract tarball attributes
tar -xzvf archive.tar.gz

zip / unzip: Standard zip compress formats packing utilities.

# Pack files into zip structure
zip -r backup.zip config/

# Unpack archive content files
unzip backup.zip

9. I/O Redirection & Piping

>: Overwrites standard output streams into target files.

echo "init" > database.config

>>: Appends standard output streams onto target files.

echo "LOG_LEVEL=debug" >> .env

| (Pipe): Passes the stdout stream output of one command as input to the next command.

# Filter process lists matches directly
ps aux | grep "postgres"

2>&1: Combines Standard Error (stderr - 2) and Standard Output (stdout - 1) streams into one single output stream.

./build.sh > output.log 2>&1

10. Shell Environment & Variables

export: Sets variables for the shell and child processes.

export NODE_ENV=production

echo: Prints text arguments to standard output.

echo "The current path is $PATH"

env: Displays all active environment variables.

env

Quick Reference

Linux Directory Layout

Command Line Keyboard Shortcuts

File Permission Octals

R (Read)     = 4
W (Write)    = 2
X (Execute)  = 1

Permission Combos:
7 = Read + Write + Execute (4+2+1)
6 = Read + Write (4+2)
5 = Read + Execute (4+1)
4 = Read Only (4)

User Groups sequence: Owner | Group | Others
Example: chmod 755 script.sh
  - Owner (7): Read + Write + Execute
  - Group (5): Read + Execute
  - Others (5): Read + Execute