Ubuntu Unleashed 2013 Edition: Covering 12.10 and 13.04, Eighth Edition

Changing Runlevels

After making changes to system services and runlevels, you can use the telinit command to change runlevels on-the-fly on a running Ubuntu system. Changing runlevels this way enables system administrators to alter selected parts of a running system to make changes to the services or to put changes into effect that have already been made (such as reassignment of network addresses for a networking interface).

For example, a system administrator can quickly change the system to maintenance or single-user mode by using the telinit command with its S option like this:

matthew@seymour:~$ sudo telinit S

The telinit command uses the init command to change runlevels and shut down currently running services.

After booting to single-user ...