Linux Pocket Guide

Becoming the Superuser

Normal users, for the most part, can modify only the files they own. One special user, called the superuser or root, has full access to the machine and can do anything on it. To become the superuser, log in as yourself and type:

$ su -l
Password: ********
#

You will be prompted for the superuser password (which we presume you know, if it’s your computer). Your shell prompt will change to a hash mark (#) to indicate you are the superuser. When finished executing commands as the superuser, type ^D or run exit to end the superuser shell and become yourself again.

This is the simplest way to obtain superuser privileges on the system. There are other programs for doing so which offer more control, such as sudo, but they are beyond the scope of this book.

If you provide a username to su:

$ su -l jones
Password: ********

you can become that user (provided you know her password).

Useful options
-l	Run a login shell. You almost always want this option, so root’s proper search path is set.
-m	Preserve your current environment variables in the new shell.
-c command	Run just this command (as the other user) and exit. If you need to do this a lot, read the sudo manpage.
-s shell	Run the given shell (e.g., /bin/bash).