We would like to determine your familiarity with Linux and bash. Can you give a brief explanation of what these commands do or are used for?

1. chmod
2. ssh
3. scp
4. su
5. rsync
6. curl
7. wget
8. ftp
9. rm
10. crontab
11. chown
12. export
13. cd
14. ln
15. yum
16. ls
17. tar
18. mkdir
19. df