Commonly Used Linux Commands

Notes on some of the most commonly used Linux Commands.

1. ls - List Directory Contents

Displays files and directories within a given directory.

• Popular flags:

  • -l: Long listing format (permissions, owner, size, etc.)

  • -a: Show all files, including hidden files

  • -h: Human-readable file sizes

2. cd - Change Directory

Used to navigate between directories.

• Popular usage:

  • cd /path/to/directory: Navigate to a specific directory

  • cd ..: Move to the parent directory

  • cd ~: Move to the home directory

3. pwd - Print Working Directory

Displays the full path of the current directory.

• Popular usage:

  • No common flags; it simply prints the path of your current directory.

4. cp - Copy Files and Directories

Copies files or directories from one location to another.

• Popular flags:

  • -r: Recursive copy (used for directories)

  • -v: Verbose (shows the progress of the copy)

  • -i: Interactive (prompts before overwriting files)

5. mv - Move or Rename Files and Directories

Moves files or directories to a new location or renames them.

• Popular flags:

  • -v: Verbose (shows the progress of the move)

  • -i: Interactive (prompts before overwriting files)

6. rm - Remove Files or Directories

Deletes files or directories.

• Popular flags:

  • -r: Recursive (used to delete directories and their contents)

  • -f: Force delete (no confirmation prompts)

  • -v: Verbose (shows what is being deleted)

7. chmod - Change File Permissions

Modifies the read, write, and execute permissions for files and directories.

• Popular flags:

  • -R: Recursive (change permissions for all files in a directory)

8. chown - Change File Ownership

Changes the ownership of a file or directory to a different user or group.

• Popular flags:

  • -R: Recursive (change ownership for all files in a directory)

  • --from=<current_owner>: Change ownership from a specific user

9. ps - Process Status

Shows information about the running processes.

• Popular flags:

  • -e: Show information for all processes

  • -f: Full-format listing

  • -aux: Displays detailed information about processes

10. top - Real-Time System Resource Usage

Shows a real-time view of system processes, CPU, and memory usage.

• Popular flags:

  • -d <time>: Set delay time between updates

11. cat - Concatenate and Display File Contents

Displays the contents of a file.

• Popular flags:

  • -n: Number all output lines

  • -E: Display $ at the end of each line

12. grep - Search Through Text

Searches for specific patterns in files or text.

• Popular flags:

  • -i: Case-insensitive search

  • -r: Recursive (search in all subdirectories)

  • -v: Invert match (show lines that do not match the pattern)

13. find - Search for Files and Directories

Searches for files and directories based on various criteria.

• Popular flags:

  • -name <name>: Search for a file by name

  • -type <d|f>: Search by file type (d for directory, f for file)

  • -exec <command>: Execute a command on each file found

14. sudo - Superuser Do

Runs commands with elevated (root) privileges.

• Popular usage:

  • sudo <command>: Run a command with root privileges

15. apt - Package Manager for Debian-Based Systems

Used to manage software packages.

• Popular flags:

  • update: Updates the package list

  • upgrade: Upgrades all installed packages to the newest versions

  • install <package>: Installs a new package

16. df - Disk Space Usage

Shows the available and used disk space on mounted filesystems.

• Popular flags:

  • -h: Human-readable output

  • -T: Show the file system type

17. du - Disk Usage

Estimates and displays the space used by files and directories.

• Popular flags:

  • -h: Human-readable output

  • -s: Summarize the total size of a directory

18. tar - Archive Files

Used for creating and extracting archives.

• Popular flags:

  • -c: Create a new archive

  • -x: Extract files from an archive

  • -v: Verbose (show the progress)

  • -z: Compress the archive using gzip

19. wget - Download Files from the Web

Downloads files from the web via HTTP, HTTPS, and FTP.

• Popular flags:

  • -q: Quiet (no output)

  • -O <file>: Output the download to a specific file name

20. ssh - Secure Shell

Used for remote login to another machine.

• Popular flags:

  • -p <port>: Specify the port number

  • -i <identity_file>: Use a specific identity file (private key) for authentication

21. man - Manual Pages

Displays the manual for a command.

• Popular usage:

  • man <command>: Show the manual page for a specific command