The 20 most likely Linux commands you'll see on the Linux + test.

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Here are 20 Linux commands commonly encountered in the CompTIA Linux+ certification exam, focusing on essential system administration, file management, and troubleshooting tasks. These commands are selected based on their relevance to the exam objectives, such as system configuration, user management, file operations, and basic scripting.


1. **ls** - Lists directory contents.

   - Example: `ls -la` (shows all files, including hidden, with detailed permissions).


2. **cd** - Changes the current directory.

   - Example: `cd /etc` (navigates to the /etc directory).


3. **pwd** - Prints the current working directory.

   - Example: `pwd` (displays the full path of the current directory).


4. **cp** - Copies files or directories.

   - Example: `cp file1.txt file2.txt` (copies file1.txt to file2.txt).


5. **mv** - Moves or renames files or directories.

   - Example: `mv file1.txt /tmp` (moves file1.txt to /tmp).


6. **rm** - Removes files or directories.

   - Example: `rm -r directory` (recursively deletes a directory and its contents).


7. **mkdir** - Creates a new directory.

   - Example: `mkdir new_folder` (creates a directory named new_folder).


8. **rmdir** - Removes empty directories.

   - Example: `rmdir empty_folder` (deletes an empty directory).


9. **cat** - Concatenates and displays file contents.

   - Example: `cat /etc/passwd` (displays the contents of the passwd file).


10. **less** - Views file contents page by page.

    - Example: `less /var/log/syslog` (allows scrolling through the syslog file).


11. **grep** - Searches for patterns in files or output.

    - Example: `grep "error" /var/log/syslog` (finds lines containing "error" in syslog).


12. **find** - Searches for files in a directory hierarchy.

    - Example: `find / -name "config.txt"` (locates config.txt anywhere on the system).


13. **chmod** - Changes file or directory permissions.

    - Example: `chmod 755 script.sh` (sets execute permissions for owner and read/execute for others).


14. **chown** - Changes file or directory ownership.

    - Example: `chown user1 file.txt` (changes the owner of file.txt to user1).


15. **useradd** - Creates a new user account.

    - Example: `useradd -m newuser` (creates newuser with a home directory).


16. **passwd** - Changes a user’s password.

    - Example: `passwd newuser` (sets or updates the password for newuser).


17. **ps** - Displays information about active processes.

    - Example: `ps aux` (shows all running processes with detailed info).


18. **top** - Displays real-time system processes and resource usage.

    - Example: `top` (interactive process viewer).


19. **systemctl** - Manages systemd services.

    - Example: `systemctl start apache2` (starts the Apache web server service).


20. **df** - Reports disk space usage.

    - Example: `df -h` (displays disk usage in a human-readable format).


### Notes:

- These commands align with Linux+ objectives, covering file management, permissions, user administration, and system monitoring.

- Practice using options (e.g., `-r`, `-l`, `-h`) as they’re often tested.

- For deeper understanding, combine commands (e.g., `grep` with `pipe` or `find` with `exec`).

- If you need specific examples or explanations for any command, let me know!

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