Reference guide to the most essential Linux commands — ideal for sys admins, developers, DevOps engineers, and cybersecurity professionals. This cheat sheet will help streamline your command-line workflow.
File and Directory Operations
Command
Description
ls
List contents of the current directory
ls -l
List with detailed (long) format
cd /path/to/dir
Change current directory
pwd
Display present working directory
mkdir new_folder
Create a new directory
rm file.txt
Remove a file
rm -r folder/
Recursively remove a directory and its contents
touch file.txt
Create a new, empty file
cp source dest
Copy a file or directory
mv old new
Move or rename a file or directory
Viewing & Editing Files
Command
Description
cat file.txt
Output file contents to the terminal
less file.txt
View file one screen at a time (scrollable)
head file.txt
Show the first 10 lines of a file
tail file.txt
Show the last 10 lines of a file
nano file.txt
Edit file using Nano (beginner-friendly)
vim file.txt
Edit file using Vim (advanced editor)
Permissions & Ownership
Command
Description
chmod +x script.sh
Make a script executable
chmod 755 file
Set read/write/execute permissions (owner), and read/execute (group, others)
chown user:group file
Change file ownership
System Information
Command
Description
uname -a
Show system and kernel information
top / htop
Real-time process and system monitoring
df -h
Display disk space usage (human-readable)
free -h
Show memory usage
uptime
Show how long the system has been running
User and Process Management
Command
Description
whoami
Display current logged-in user
id
Show user ID (UID), group ID (GID), and groups
ps aux
List all running processes
kill PID
Terminate a process by its PID
sudo command
Run command with superuser privileges
adduser username
Add a new user
passwd username
Change a user’s password
Networking Commands
Command
Description
ip a
Display network interfaces and IP addresses
ping domain.com
Send ICMP packets to test connectivity
curl https://example.com
Fetch data from a URL
netstat -tulpn
Show active listening ports and services (legacy; use ss for modern systems)
ssh user@host
Connect to a remote host via SSH
Package Management
Debian/Ubuntu (APT)
Command
Description
sudo apt update
Update package lists
sudo apt upgrade
Upgrade installed packages
sudo apt install package
Install a new package
sudo apt remove package
Remove a package
Red Hat/CentOS (YUM/DNF)
Command
Description
sudo yum install package
Install package (YUM)
sudo dnf upgrade
Upgrade packages (DNF, successor to YUM)
Searching Files
Command
Description
find / -name file.txt
Search for a file by name starting from root
grep 'pattern' file.txt
Search for a text pattern in a file
locate file.txt
Quickly find file paths using an indexed database (updatedb required)
Keyboard Shortcuts & History
Shortcut
Description
Ctrl + C
Cancel the current running process
Ctrl + D
Logout of terminal or send EOF (End of File)
Ctrl + R
Search command history interactively
!!
Repeat the last command
!abc
Run the most recent command starting with abc
Notes
Most of these commands are compatible across major Linux distributions.
Prefix commands with sudo where administrative privileges are required.
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