Unix Commands Cheat Sheet

Unix commands cheat sheet is an essential resource for system administrators, developers, and anyone working with Unix-based systems. Mastering these commands can significantly improve efficiency, troubleshoot issues faster, and automate routine tasks. This comprehensive guide covers the most commonly used Unix commands, their functionalities, options, and tips to help users navigate the Unix environment with confidence.

Introduction to Unix Commands

Unix commands are the backbone of interacting with Unix-like operating systems such as Linux, macOS, and BSD. These commands perform a variety of tasks ranging from file management to system monitoring and process control. Understanding the basic syntax and options for these commands is crucial for effective system management.

Basic File and Directory Management Commands

Listing Files and Directories

• ls: Lists directory contents.

Common options:

• ls -l: Detailed list including permissions, owner, size, and modification date.


• ls -a: Includes hidden files (those starting with a dot).


• ls -lh: Human-readable sizes with detailed info.

Creating Files and Directories

• touch: Creates an empty file or updates the timestamp of an existing file.


• mkdir: Creates a new directory.

Examples:

touch newfile.txt

mkdir new_directory

Removing Files and Directories

• rm: Deletes files or directories.

Options:

• rm -r: Recursively removes directories and their contents.


• rm -f: Forces deletion without prompts.

Examples:

rm file.txt

rm -rf directory_name

Copying and Moving Files

• cp: Copies files or directories.

Options:

• cp -r: Recursively copies directories.

Examples:

cp source.txt destination.txt

cp -r dir1 dir2

Renaming Files

• mv: Moves or renames files and directories.

Example:

mv oldname.txt newname.txt

Viewing and Manipulating File Content

Displaying File Contents

• cat: Concatenates and displays file contents.


• less: Views file contents one screen at a time with navigation.


• more: Similar to less but with limited navigation features.

Examples:

cat file.txt

less largefile.log

Searching Within Files

• grep: Searches for patterns within files.

Common usage:

grep "search_term" filename

grep -r "pattern" directory/   Recursive search

Counting Lines, Words, and Characters

• wc: Counts lines, words, and characters.

Examples:

wc -l file.txt   Lines

wc -w file.txt   Words

wc -c file.txt   Characters

File Permissions and Ownership

Changing Permissions

• chmod: Modifies file permissions.

Examples:

chmod 755 script.sh   rwxr-xr-x

chmod u+x file.sh   Adds execute permission for the owner

Changing Ownership

• chown: Changes file owner and group.

Examples:

chown user:group file.txt

Process Management Commands

Viewing Processes

• ps: Displays current processes.

Common options:

• ps aux: Shows all processes with detailed info.


• ps -ef: Another format for process listing.

Monitoring Real-Time Processes

• top: Displays real-time process activity.


• htop: An enhanced, interactive version of top (if installed).

Terminating Processes

• kill: Sends signals to processes to terminate or restart them.

Examples:

kill PID   Graceful termination

kill -9 PID   Forceful kill

Disk Usage and Filesystem Commands

Checking Disk Space

• df: Reports filesystem disk space usage.

Options:

df -h   Human-readable format

Checking Directory Size

• du: Shows disk usage of files/directories.

Examples:

du -sh directory_name   Summarized, human-readable size

Mounting and Unmounting Filesystems

• mount: Mounts a filesystem.


• umount: Unmounts a filesystem.

Examples:

mount /dev/sdX1 /mnt/point

umount /mnt/point

User Management Commands

Adding and Removing Users

• adduser: Adds a new user (varies by distribution).


• deluser: Removes a user.

Switching Users

• su: Switches to another user.


• sudo: Executes commands with superuser privileges.

Examples:

su - username

sudo apt update

Managing User Groups

• groupadd: Creates a new group.


• groupdel: Deletes a group.


• usermod: Modifies user account details, including group memberships.

Networking Commands

Checking Network Configuration

• ifconfig: Displays network interfaces (deprecated in favor of ip command).


• ip addr: Shows IP addresses and interface info.

Testing Network Connectivity

• ping: Checks if a host is reachable.

Example:

ping google.com

Tracing Network Routes

• traceroute: Shows the path packets take to reach a host.

Managing Open Ports and Services

• netstat: Displays network connections and listening ports.


• ss: Modern replacement for netstat.

Examples:

ss -tuln   List all listening ports

Compression and Archiving Commands

Creating Archives

• tar: Archives files and directories.

Examples:

tar -cvf archive.tar directory/

tar -czvf archive.tar.gz directory/   Compressed with gzip


Frequently Asked Questions


What are some essential Unix commands for navigating the file system?
Common navigation commands include 'ls' to list directory contents, 'cd' to change directories, 'pwd' to print the current directory, and 'tree' to visualize directory structures.
How do I view the contents of a file in Unix?
Use commands like 'cat' to display the entire file, 'less' or 'more' for paginated viewing, and 'head' or 'tail' to see the beginning or end of a file.
What is the purpose of the 'grep' command in Unix?
'grep' searches for specific patterns or strings within files, making it useful for filtering and finding information quickly.
How can I manage processes using Unix commands?
Use 'ps' to list running processes, 'kill' to terminate processes, 'top' or 'htop' for real-time process monitoring, and 'killall' to stop processes by name.
What are some commands for file manipulation in Unix?
Commands like 'cp' to copy files, 'mv' to move or rename, 'rm' to delete, and 'mkdir' to create new directories are essential for file management.
How do I search for files or directories in Unix?
Use 'find' to locate files and directories based on various criteria, and 'locate' for quick searches in a pre-built database. 'which' helps find the path of executable commands.