Linux Pocket Guide

Users and Superusers

Linux is a multiuser operating system. On a given computer, each user is identified by a unique username, like “smith” or “funkyguy,” and owns a (reasonably) private part of the system for doing work. There is also a specially designated user, with username root, who has the privileges to do anything at all on the system. Ordinary users are restricted: though they can run most programs, in general they can modify only the files they own. The superuser, on the other hand, can create, modify, or delete any file and run any program.

Some commands in this book can be run successfully only by the superuser. In this case, we use a hash mark (#) as the shell prompt:

# command goes here

Otherwise, we will use the dollar sign prompt indicating an ordinary user:

$ command goes here

To become the superuser, you needn’t log out and log back in; just run the su command (see Becoming the Superuser) and provide the superuser password:

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