runit - a UNIX process no 1
runit must be run
as Unix process no 1. It performs the system’s booting, running, and shutdown
in three stages:
runit runs /etc/runit/1 and waits for it to terminate.
The system’s one time tasks are done here. /etc/runit/1 has full control
of /dev/console to be able to start an emergency shell if the one time
initialization tasks fail. If /etc/runit/1 crashes, or exits 100, runit
will skip stage 2 and enter stage 3.
runit runs /etc/runit/2, which
should not return until system shutdown; if it crashes, or exits 111, it
will be restarted. Normally /etc/runit/2 starts runsvdir(8). runit is able
to handle the ctrl-alt-del keyboard request in stage 2, see below.
runit is told to shutdown the system, or stage 2 returns, it terminates
stage 2 if it is running, and runs /etc/runit/3. The systems tasks to shutdown
and possibly halt or reboot the system are done here. If stage 3 returns,
runit checks if the file /etc/runit/reboot exists and has the execute by
owner permission set. If so, the system is rebooted, it’s halted otherwise.
If runit receives the ctrl-alt-del keyboard request and the file
/etc/runit/ctrlaltdel exists and has the execute by owner permission set,
runit runs /etc/runit/ctrlaltdel, waits for it to terminate, and then sends
itself a CONT signal.
runit only accepts signals in stage 2.
receives a CONT signal and the file /etc/runit/stopit exists and has the
execute by owner permission set, runit is told to shutdown the system.
runit receives an INT signal, a ctrl-alt-del keyboard request is triggered.
runit-init(8), runsvdir(8), runsvchdir(8), sv(8), runsv(8), chpst(8),
Gerrit Pape <email@example.com>
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