Essential Linux Command Cheat Sheet: 20+ Must‑Know Commands for System Operations

1. Find a file

find / -name filename.txt

– Search for filename.txt under the root directory.

2. Check if a program is running

ps -ef | grep tomcat

– List all processes related to Tomcat.

3. Terminate a process

kill -9 19979

– Force‑kill the process with PID 19979.

4. List files including hidden ones

ls -al

5. Show current working directory

pwd

6. Copy a directory recursively

cp -r sourceFolder targetFolder

7. Create a directory

mkdir newfolder

8. Remove an empty directory

rmdir deleteEmptyFolder

9. Delete files or directories recursively

rm -rf deleteFile

10. Move or rename files

mv /temp/movefile /targetFolder

– Move a file; mv oldNameFile newNameFile – Rename a file.

11. Switch user

su -username

12. Change file permissions

chmod 777 file.java

– Set read, write, and execute permissions for everyone.

13. Compress files

tar -czf test.tar.gz /test1 /test2

14. List contents of a tar.gz archive

tar -tzf test.tar.gz

15. Extract a tar.gz archive

tar -xvzf test.tar.gz

16. View the first 10 lines of a file

head -n 10 example.txt

17. View the last 10 lines of a file

tail -n 10 example.txt

18. Follow a log file

tail -f example.log

– Continuously display new log entries.

19. Launch the Vi editor

vi

20. Show current system time

date

– Displays day, month, date, time, timezone, and year.

21. Format date output

date +"%Y-%m-%d"

– Prints the date as YYYY-MM-DD.

22. Extract a zip file

unzip -oq archive.zip

23. Count threads of a process

ps -Lf portNumber | wc -l