Finally I sucked up the courage and defined in /boot/loader.conf
init_exec=/root/bin/init_exec.sh
which contains
#!/usr/local/bin/execlineb -S0
redirfd -wnb 1 /m/fifo/catch_all
redirfd -r - /dev/null
fdmove -c 2 1
exec -c /sbin/s6/svscan -t 0 -s /s/scan
And finally /sbin/s6-svscan runs as pid 1.
That's awesome! So, if I understand correctly:
- /sbin/init is still the first program loaded by the kernel, it's
the stock FreeBSD thing that performs FreeBSD-specific setups
- if there is an init_exec entry in /boot/loader.conf, /sbin/init
execs into its value, which allows you to run a different pid 1
for the lifetime of the machine.
If that's really how it works, it's incredibly good, and would make
s6-freebsd-init a breeze to write.
The necessary modifications to turn s6-linux-init into s6-freebsd-init
would just be:
- Comment out kbspecials() and its invocations:
https://github.com/skarnet/s6-linux-init/blob/master/src/init/s6-linux-init.c#L70
(does FreeBSD's /sbin/init set up CAD handling and other related
console things?)
- Port the mount() and umount() invocations, replacing mount with the
correct FreeBSD way of mounting a tmpfs:
https://github.com/skarnet/s6-linux-init/blob/master/src/init/s6-linux-init.c#L209
- Port the final reboot() call:
https://github.com/skarnet/s6-linux-init/blob/master/src/shutdown/s6-linux-init-hpr.c#L81
and all the rest should work as is. It's a game-changer.
foreground { /sbin/shutdown -o -r now } # this invokes reboot rather
than send a signal to init.
I'd greatly appreciate advice as to completing a clean shutdown?
My current approach is, indeed, to keep s6-svscan running as pid 1,
without making it exec into anything else, for the whole lifetime of
the machine, shutdown procedure included. So yes, for a clean
shutdown, you'd just make sure to kill all processes, then unmount
filesystems (and remount / read-only), then invoke reboot/poweroff
directly. That is how the current s6-linux-init works; I don't see a
reason why it shouldn't work on FreeBSD.
PS This journey commenced with the simple wish to safely rotate apache
logs, now I'm hooked on s6-rc (and the peace of mind it brings)
Glad you like it :)
--
Laurent
