passwd [option(s)] [username]
Users may change their own passwords at any time using this command. Furthermore, the administrator root can use the command to change the password of any user on the system.
su [option(s)] [username]
The su command makes it possible to log in under a different user name from a running session. When using the command without specifying a user name, you will be prompted for the root password. Specify a user name and the corresponding password to use the environment of the respective user. The password is not required from root, as root is authorized to assume the identity of any user.
To avoid loss of data, you should always use this program to shut down your system.
Does the same as halt with the difference that the system performs an immediate reboot.
This command cleans up the visible area of the console. It has no options.