Customizing UNIX system startup

Changing to single-user state (system state s)

Some administrative functions can be done only when the system is in single-user state.

The recommended way to enter single-user state to run the shutdown -is command. This command executes all the files in the /etc/rc0.d directory by invoking the /sbin/rc0 procedure. The shutdown command accomplishes, among other things, the following:

closes all open files and stops all user processes
stops all daemons and services
writes all system buffers out to the disk
unmounts all filesystems necessary for multiuser operations, but not needed in single-user state (such as /home)

NOTE: An init 1 or an init s issued from multiuser mode functions in a similar manner, but does not unmount filesystems would and does not kill all processes and services.

Use this procedure to change to single-user state:

Log in as root.
Navigate to the / (root) directory.
Execute:

shutdown -is
At the prompt to continue, type y and press <Esc> .
After the change to single-user state is complete, you are prompted for the root password.
Type the root password and press <Esc>; You are now ready to perform tasks that should be done only in single-user state.