Simple linux commands but powerful

1.useradd name ( create user)
2.useradel name (delete user)
3.ifconfig (check ip )
4.ssh (logging to remote computer)
eg ssh root@192.168.1.1
passwd:
if u want to enable gui
ssh -X root@192.168.1.1

5.ls (listing files)
ls -a (Hidden files)
ll - lZ (will context of file)
ls -ltr (last update on files)

6. Disabling selinux
vim /etc/sysconfig/selinux make it diabaled in that file reboot the system

7. fdisk (Used to view file system as well as used to create file system)
eg fdisk /dev/hda

8.du (used to check the file size)

9.passwd name (to create or change passwd)

10.ntsysv (to enable or disable things from startup redhat based system)

11 .system-config-dispaly( redhat and fedora rewriting gui must done in int3 mode)

12 . configuring printer
Open a Browser type localhost:631 (common for all unix like os which supports cups)
13. netstat | lptn or u can use nmap (which which will work in remote as well as Local system.

14. /etc/init.d /service (start ,stop,restart)
15. ifconfig eth0 192.168.1.2 netmask 255.255.255.0
Assign IP/Subnet to eth0.