:: Re: [DNG] Reaping orphan processes.
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Author: Steve Litt
To: dng
Subject: Re: [DNG] Reaping orphan processes.
Rainer Weikusat via Dng said on Mon, 06 Mar 2023 22:11:57 +0000

>Antoine <tacredips@???> writes:
>> On Monday, 6 March at 16:58, Hendrik Boom wrote:
>>>On Mon, Mar 06, 2023 at 07:15:23PM +0100, aitor wrote:
>>>> One of the drawbacks of sysvinit is that it cannot run daemons in
>>>> the foreground. As opposed to it, daemons supervised by runit must
>>>> necessarily run in the foreground, but often they have been
>>>> designed to run in the background with sysvinit in mind.
>>>What is the difference between 'foreground' and 'background' in this


>In this context, 'foreground' means the daemon program
>runs as child of the process which started it (which can therefore also
>wait for it to get its termination status and possibly, restart
>it). 'Background' means the daemon program (or something else) forked
>once more and the original process exited. The daemon program now runs
>in an orphaned process which is unrelated to the one which originally
>started it.
>That's a bit oversimplified (eg, a background process will usually also
>change its session) but generally correct.

I think the preceding is the answer to the original question. I'd add
that the background process backgrounds itself through a double fork to
reparent itself to PID1 and to give up its attachment to any terminal.

Traditionally, this type of daemon would remain in foreground until it
was functional, and then doublefork itself, at which time sysvinit
would run the next daemon.


Steve Litt
Autumn 2022 featured book: Thriving in Tough Times