Becoming Root

As you learned inSection 6.1, “User Concept”, some tasks in Linux require root permissions, otherwise they cannot be executed.

Using su

In order to temporarily become root in a shell, proceed as follows:

Enter su. You are prompted for the root password.
Enter the password. If you mistyped the root password, the shell displays a message. In this case, you have to re-enter su before retyping the password. If your password is correct, a hash symbol # appears at the end of the prompt, signaling that you are acting as root now.
Execute your task. For example, transfer ownership of a file to a new user which only root is allowed to do:
```
chown wilber kde_quick.xml
```
After having completed your tasks as root, switch back to your normal user account. To do so, enter
```
exit
```
The hash symbol disappears and you are acting as “normal” user again.

Using sudo

Conversely, you can also use sudo (superuser “do”) to execute some tasks which normally are for roots only. With sudo, administrators can grant certain users root privileges for some commands. Depending on the system configuration, users can then run root commands by entering their normal password only. Due to a timestamp function, users are only granted a “ticket” for a restricted period of time after having entered their password. The ticket usually expires after a few minutes. In openSUSE, sudo requires the root password by default (if not configured otherwise by your system administrator).

For users, sudo is convenient as it prevents you from switching accounts twice (to root and back again). To change the ownership of a file using sudo, only one command is necessary instead of three:

sudo chown wilber kde_quick.xml

After you have entered the password which you are prompted for, the command is executed. If you enter a second root command shortly after that, you are not prompted for the password again, because your ticket is still valid. After a certain amount of time, the ticket automatically expires and the password is required again. This also prevents unauthorized persons from gaining root privileges in case a user forgets to switch back to his normal user account again and leaves a root shell open.