Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Administering a System: Booting and Shutdown

Shutting Down Systems

Chapter 5 525

• Veriﬁes that the user attempting to shut down the system has

permission to do so (checks the /etc/shutdown.allow ﬁle).

• Changes the current working directory to the root directory (/).

• Runs the sync command to be sure that ﬁle system changes still in

memory are updated in the superblocks and ﬁle system structures on

disk. This is one of shutdown’s most important functions!

• Sets the real user ID to that of the superuser (see setuid (2) for

information on user IDs).

• Sends a broadcast message to all users currently logged in to the

system telling them that the system is about to be shut down. There

is a default broadcast message, but you can specify your own if you

prefer.

• /sbin/rc is executed to shut down subsystems, unmount ﬁle

systems, and perform other tasks to bring the system to run level 0,

where it is safe to power off your system if you do not plan to

immediately reboot it.

✓ If your system is an NFS cluster server, before /sbin/rc is

executed, the optional -o argument is used to determine whether

or not to also reboot the NFS cluster clients served by your

system. By default (when -o is not speciﬁed), all clients served by

this server will be rebooted too. When -o is speciﬁed, only the

server will be rebooted. Once the decision about whether or not to

reboot the clients has been made, /sbin/rc is executed.

✓ If your system is an NFS cluster client, /sbin/rc brings the

system down to run level 2 (single-user state is not permitted on

an NFS cluster client).

• Finally, if your system is not an NFS cluster client, and you are not

shutting your system down to single-user mode (see “Single-User

Mode” on page 527), the program /sbin/reboot is executed to halt

your system or reboot it if the -h or -r option (respectively) was

speciﬁed.

Power Failure

Not every shutdown can be planned for. An unexpected power failure is

an example of an unplanned shutdown.