Introduction -

In the recent few weeks, I have started using Linux on a daily basis. As we all know, someone using Linux needs to have a good grasp on the commands. Hence, I thought of preparing something similar to a cheatsheet for some of the most used commands -

FILE & DIRECTORIES -

1. ls - directory listing (list all files/folders on current dir)
2. ls -l - formatted listing
3. ls -la - formatted listing including hidden files
4. cd dir - change directory to dir (dir will be directory name)
5. cd .. - change to the parent directory
6. cd ../dir - change to dir in the parent directory
7. cd - change to the home directory
8. pwd - show current directory
9. mkdir dir - create a directory dir
10. rm file - delete a file
11. rm -f dir - force remove the file
12. rm-r dir - delete directory dir
13. rm-rf dir - remove directory dir
14. cp file1 file2 - copy file1 to file2
15. mv file1 file2 - rename file1 to file2
16. mv file1 dir/file2 - move file1 to dir as file2
17. touch file - create or update file
18. cat file - output contents of the file
19. cat > file - write standard input into the file
20. cat >> file - append standard input into the file
21. tail -f file - output contents of the file as it grows

NETWORKING -

1. ping host - ping the server
2. who is domain - get whois for domain
3. dig domain - get DNS for domain
4. dig -x host - reserve lookup host
5. wget file - download file
6. wget -c file - continue stopped download
7. wget -r url - recursively download files from url
8. curl url - outputs the webpage from url
9. curl -o meh.html url - writes the page to meh.html
10. ssh user@host - connect to host as user
11. ssh -p port user@host - connect using port
12. ssh -D user@host - connect & use bind port

PROCESSES -

1. ps- display currently active processes
2. ps aux - detailed outputs
3. kill pid - kill process with process id (pid)
4. killall proc - kill all processes named proc

SYSTEM INFO -

1. date - show current date/time
2. uptime- show uptime
3. whoami - who you're logged in as
4. w- display who is online
5. cat /proc/cpuinfo - display CPU info
6. cat /proc/meminfo - memory info
7. free- show memory and swap usage
8. du- show directory space usage
9. du -sh - displays readable sizes in GB
10. df - show disk usage
11. uname -a - show kernel config

COMPRESSING -

1. tar cf file.tar files - tar files into file.tar
2. tar xf file.tar - untar into the current directory
3. tar tf file.tar - show contents of the archive
   options:
   c - create an archive
   t - table of contents
   x - extract
   z - use zip/gzip
   f - specify the filename
   j - bzip2 compression
   w - ask for confirmation
   k - do not overwrite
   T - files from the file
   v - verbose
   

PERMISSIONS -

chmod octal file - change permissions of file
4 - read (r)
2 - write (w)
1 - execute (x)

order: owner/group/world

chmod 777 - rwx for everyone
chmod 555 - rw for owner / rx for group

SOME OTHERS -

1. grep pattern files - search in files for pattern
2. grep -r pattern dir - search for pattern recursively in dir
3. locate file - find all instances of file
4. whereis app - show possible location of app
5. man command - show manual page for command