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Date: Sat, 24 Oct 2020 05:25:53 +0000
From: Colin Booth <colin@heliocat.net>
To: supervision@list.skarnet.org
Subject: Re: Can you use s6-rc with the sysvinit PID1?
Message-ID: <20201024052553.GC15636@cathexis.xen.prgmr.com>
References: <20201023124847.66962dcb@mydesk.domain.cxm>
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On Fri, Oct 23, 2020 at 12:48:47PM -0400, Steve Litt wrote:
> Hi all,
> 
> If I use sysvinit's PID1, is it possible for me to use s6-rc by
> declaring an s6-rc program in /etc/inittab?
> 
> Also, and this is offtopic, is there a way to tell sysvinit not to run
> the programs in /etc/rc.d/rc3.d or whatever? This would make it trivial
> to switch between an sysvinit initted system and an s6-rc/s6 supervised
> system just by commenting in or out the inittab entry and switching
> sysvinit to looop /etc/rc.d/rc3.d?
> 
> Thanks,
> 
> SteveT
> 
Yes. In your /etc/inittab call a script that backgrounds the rc call
hanging on some event. Here's an execline fragment that'll do what you
want, though it could obviously be made a lot better by taking advantage
of the native readyness notification that s6-svscan provides instead of
sleeping for a second.

background {
  foreground { sleep 1 }
  foreground { s6-rc-init /path/to/scandir }
  s6-rc change up
}
s6-svscan /path/to/scandir

Jam that into the startup script that you use for booting your
supervision tree and you'll be good to go.

-- 
Colin Booth