[systemd-devel] service.d/.conf files and multi-valued options

[Christian Seiler]

Am 2015-01-23 14:27, schrieb Lennart Poettering:
>> Yes, it does, although only in the general systemd.unit(5), not in 
>> the
>> specific options, so maybe it's not that easy to find.
>
> Actually, it kinda says it in the specific options. From the
> explanation of ExecStart=:
>
> "...If the empty string is assigned to this option, the list of
> commands to start is reset, prior assignments of this option will 
> have
> no effect..."

Oh, I didn't see that while skimming the man page. Still, I think a
tutorial manpage as I described (different ways to override distro
configuration) would be a good idea. Would you accept a patch for
something like that? If so, what should the man page be called?

> And at the explanation of ExecStartPre= says the syntax is identical
> to ExecStart=. So I think we are covered here.

No, sure, I don't think ExecStartPre= needs additional information,
I just didn't see the sentence in ExecStart=, sorry about that.

>> Btw. it would also be nice to have a possibility to just remove a
>> specific entry from a list, not to reset it completely. Probably 
>> less
>> for things like Exec*=, but more for After=/Before=/...
>>
>> For example, if there's a unit with After=b.service c.service und as
>> an admin I want to not order it after c.service, I will have to 
>> first
>> reset the list (empty After=) and then add all the current other
>> units it orders after again. If an update then makes the unit also 
>> be
>> ordered after d.service to fix some other bug, the local setting 
>> will
>> override the After=d.service too...
>>
>> Maybe something like 'After-=c.service'? Although that would 
>> probably
>> break traditional ini parsers trying to process unit files...
>
> I'd be very careful with coming up with more and more syntaxes like
> this. People have also requested "+=", to append things to existing
> lines.

I agree that I also don't like that syntax, but:

> I think for simplicity's sake the right approach to remove parts of a
> unit file is to copy it from /usr to /etc, and then modify it
> there. .d/ is not the answer to everything. I am aware of course that
> copying the files from /usr to /etc will also disconnect you from
> new unit files added by package updates, but I guess you cannot have 
> a
> cake and eat it too...

But if I want to add something to After=/Before=/..., I can easily do
that with a drop-in just containing After=foo.service. And that's 
indeed
very useful, I've used that a couple of times. So for symmetry reasons,
I think the converse would also be quite useful (although I haven't
needed it that often). I don't have a good idea for the syntax just 
now,
but would you be opposed to at least adding 'design a syntax for this'
to the TODO list?

Christian