su

su [option] [user] [shell_args]

Create a shell with the effective user ID of another user (that is, login as user). If no user is specified, create a shell for a privileged user (that is, become a superuser). Enter EOF to terminate. You can run the shell with particular options by passing them as shell_args (e.g., if the shell runs sh, you can specify -c command to execute command via sh, or -r to create a restricted shell).

su will inherit your environment settings. Administrators wishing to switch to a user's setup (perhaps to help them solve a problem) may wish to consider using this sequence:

me$ su		Switch to root
Password:		Enter root password
# su - user	Switch to other user
user$ 

Option

-

Go through the entire login sequence (i.e., change to user's environment).