Re: [gentoo-dev] pid 1 design

[Rich Freeman]

On Thu, Aug 9, 2012 at 12:00 PM, Wyatt Epp <wyatt.epp@×××××.com> wrote:
> On Thu, Aug 9, 2012 at 11:25 AM, Rich Freeman <rich0@g.o> wrote:
>> ...have an init as PID=1 that does
>> nothing but launch systemd and keep it propped up until it gets a
>> signal from systemd.  However, that could have issues I'm just not
>> thinking of.
>
> I'm not the maintainer, but this method does seem to work pretty well
> for OpenRC and our old friend baselayout-1 (so, the last decade or so,
> as I understand it).

Yes, but OpenRC basically just launches processes and considers itself
done with them.  Systemd is a bit more like a shepherd, looking after
things for their entire lifecycle.  When you use openrc to stop a
process it just runs a script which is responsible for cleaning up.
If you stop a systemd service it can try nicely first, but if any
descendant of the service is left running it will be cleaned up with a
vengeance.  If a process is supposed to be running and stops, systemd
can restart it (which makes it more like init - which restarts
anything in inittab if it dies).

Systemd isn't a like-for-like replacement for traditional inits.  It
aims to be much more, so this is a bit of an apples-to-oranges
comparison.  Again, I'm not sure that it HAS to work the way it does,
but I wouldn't dismiss their design simply because it is different.
Also again, if curious I'd probably ask on their own list, assuming it
hasn't already been answered there.

Rich