[systemd-devel] /usr vs /etc for default distro units enablement

[Andrei Borzenkov]

В Tue, 18 Nov 2014 16:22:18 +0000
Colin Guthrie <gmane at colin.guthr.ie> пишет:

> Michael Biebl wrote on 18/11/14 15:55:
> > 2014-11-18 16:30 GMT+01:00 Colin Guthrie <gmane at colin.guthr.ie>:
> >> Michael Biebl wrote on 18/11/14 15:09:
> >>> 2014-11-18 15:59 GMT+01:00 Colin Guthrie <gmane at colin.guthr.ie>:
> >>>> Didier Roche wrote on 18/11/14 13:58:
> >>>>> This would be maybe a nice way for the admin to know what's coming from
> >>>>> a distribution default or not. However, let's say I want to ensure that
> >>>>> ssh will always be available on my server, I would (even if it's in my
> >>>>> server preset) then systemctl enable openssh, no matter whatever future
> >>>>> preset updates does (like disable it in the next batch upgrade).
> >>>>
> >>>> For the avoidance of doubt, I believe that running systemctl preset
> >>>> should only ever happen on *first* install, never on upgrade or such like.
> >>>>
> >>>
> >>> And what are you going to do, if the unit file changes?
> >>> Say v1  had
> >>>
> >>> [Install]
> >>> WantedBy=multi-user.target
> >>>
> >>> and version B has
> >>> [Install]
> >>> WantedBy=foo.target
> >>
> >>
> >> Well this is an edge case I'm sure you'll agree.
> > 
> > Actually, in the short period of time (and with the currently still
> > low number of packages shipping native units) in Debian, this happened
> > more often then I'd have expected.
> > 
> > So I think we should have a better answer then just saying this is an edge case.
> 
> I still thing we should still call it an edge case tho' :)
> 
> Having a way around it is fine tho'.
> 
> >> Ultimately, with this case, doing the preset is wrong anyway. You don't
> >> want the distro choice, you want the "what the user had" choice.
> > 
> > You only want to preservce the user choice, if it deviated from the
> > distro choice. 
> 
> Well, depending on implementation that's one and the same thing. With
> the current implementation of preset, they *are* the same thing,

Not really. There is no way to distinguish between unit enabled by
presets and unit enabled by admin.

>                                                                  so I
> think my statement is valid.
> 
> > Otherwise the package state should be updated to
> > reflect the latest distro choice.
> 
> Assuming currently implementation, my script did this :)
> 
> But I can see why you'd like to encapsulate this better in a more
> automated fashion and I don't have a direct answer for this (but then I
> don't think the proposed scheme here covered the opposite case either -
> i.e. user deviating from distro choice - so IMO it's just as bad!)
> 
> Col
>