- system Info
- date
- cal
- uptime
- whoami
- uname
- cpuinfo
- meminfo
- man
- df
- du
- free
- whereis
- which
- type of listing
- process management
- ps
- kill pid
- killall proc
- bg
- fg
- file permission
- 4 - read (r)
- 2 - write (w)
- 1 - execute (x)
- order: owner / group / public
- eg:
- chmod 755
- file commands
- network