Re: initialization vs supervision

From: Laurent Bercot <>
Date: Thu, 24 Jul 2014 10:54:53 +0100

On 24/07/2014 02:49, Alex Efros wrote:
> udevd is only service started from /etc/runit/1. And, honestly, I think
> it's much simpler to just kill it at end of /etc/runit/1 and (re-)start it
> as a normal service when /etc/runit/2 will be executed, than try to
> fork/delay parts of /etc/runit/1 - because most of other normal services
> expect all parts of /etc/runit/1 already done before they'll start.
> And I'll implement this right after udevd will crash for the first time.
> Not because I think it's special and don't need supervision, but just
> because I'm usually have other, more important things to do, than forcing
> supervising to all and every service.

  What I'm reading is that you're willing to do treat udevd differently and
let it run unsupervised, and duplicate work (run udevd in stage 1 and again
in stage 2) because it's much easier. And you're right. My point is that if
it's so much easier and tempting to treat an early service differently, if
you have to jump through hoops to get something supervised, then we got the
design wrong, and I'm not satisfied with it.

> - mount.ntfs-3g
> * this one uses FUSE and it's started by mount command - is it makes
> sense or even possible to supervise it?

  Not without redesigning mount to cooperate with a supervision infrastructure.
That would be the smart thing, but would tie mount to a given choice of
process management: it's a policy desision, and you can't embed policy in
software, unless you're going the systemd way. So that's not going to happen.

> [other long-lived processes]

  Like mount.ntfs-3g, those daemons are started by various subsystems during
your machine's lifetime, and the smart thing for those subsystems would be
to tie to a supervision infrastructure, but that's their choice to make, not
ours. There's nothing for us to do here.

> So, how udevd is more important to supervise than all these apps/services?

  It's not more important; it's just not part of an integrated applicative
system that forks uncontrolled processes all over the place no matter the
underlying infrastructure. It's a simple system daemon, and it can be
supervised like any other simple system daemon; the only reason why you don't
is that it's too hard with the framework you have. Well, it's the framework's
fault, and we can provide a better one.

Received on Thu Jul 24 2014 - 09:54:53 UTC

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