rc0(1M)

rc0, rc6 -- run commands performed to stop the operating system

Synopsis

/sbin/rc0 [firmware | off | reboot]
/sbin/rc6 [firmware | off | reboot]

Description

rc0 is executed at each system state change that needs to have the system in an inactive state. It is responsible for those actions that bring the system to a quiescent state, traditionally called ``shutdown''. (For backwards compatibility, /sbin/rc0 is linked to /sbin/rc6.)

Three system states require this procedure: state 0, state 5, and state 6. Whenever a change to one of these states occurs, the rc0 procedure is run. The options are used as follows:

firmware: Go to init state 5 (the firmware state)
off: Go to init state 0 (the system halt state)
reboot: Go to init state 6 (the reboot state)

The entries in /etc/inittab, which may vary slightly on different machine types, might read something like this:

   r0:0:wait:/sbin/rc0 off 1>/dev/sysmsg 2>&1 </dev/console
   r5:5:wait:/sbin/rc0 firm 1>/dev/sysmsg 2>&1 </dev/console
   r6:6:wait:/sbin/rc0 reboot 1>/dev/sysmsg 2>&1 </dev/console

See init(1M) for complete details on init states.

Some of the actions performed by rc0 are carried out by files beginning with ``K'' in /etc/rc0.d. These files are executed in ASCII order terminating some system service. The combination of commands in rc0 and files in /etc/rc0.d determines how the system is shut down.

The recommended sequence for rc0 is:

Stop system services and daemons.
- Various system services (such as a Local Area Network or LP Spooler) are gracefully terminated.
- New services are sometimes added that should be terminated when the system is shut down or that need to do cleanup before being terminated by a SIGTERM signal. For such services the appropriate files are installed in /etc/rc0.d.
Terminate processes
- SIGTERM signals are sent to all running processes by killall(1M). Most processes stop themselves cleanly if sent SIGTERM.
Kill processes
- SIGKILL signals are sent to all remaining processes; no process can resist SIGKILL.
- At this point the only processes left are those associated with rc0 and processes 0 and 1, which are special to the operating system.
Unmount all filesystems
- Only the root filesystem (/) remains mounted.

Depending on which system state the systems end up in (0, 5 or 6), rc0 determines what happens next: for system state 0, uadmin 2 0 is run; for system state 5, uadmin 2 2 is run; for system state 6, uadmin 2 1 is run. If the /etc/inittab has not defined any other actions to be performed as in the case of system state 0, then the operating system will have nothing to do. It should not be possible to get the system's attention. The only thing that can be done is to turn off the power or possibly get the attention of a firmware monitor. The command can be used only by a privileged user.

Files

The execution by /usr/bin/sh of any files in /etc/rc0.d occurs in ASCII sort-sequence order. See rc2(1M) for more information.

References

init(1M), killall(1M), rc2(1M), shutdown(1M), uadmin(1M), uadmin(2)