[Buildroot] [PATCH 1/2] package/systemd: set machine id file instalation as optional choice

Jérémy ROSEN jeremy.rosen at smile.fr
Wed Feb 5 09:05:11 UTC 2020


So don't drop your patch ?

I still think that the approach I proposed upstream is the best one but I
am pessimistic about the chances of upsreaming...
I'll ping the issue, but don't hold your breath.

If this is rejected upstream, we might want to keep the patch locally, but
that's a subject to discuss when we reach that point.

Le lun. 3 févr. 2020 à 19:41, Bartosz Bilas <b.bilas at grinn-global.com> a
écrit :

> Nah, sorry guys - I've been mistaken for the email so please ignore the
> previous message then.
>
>
> Best
> Bartek
> On 03.02.2020 19:34, Bartosz Bilas wrote:
>
> Hi everyone,
>
> I had finally a couple of time to double-check that and I agree with
> Jeremy that I was wrong therefore let's reject this patch as it turned out
> as an unthought idea.
>
>
> Best
> Bartek
> On 03.02.2020 19:28, Bartosz Bilas wrote:
>
> Hello everyone,
>
> let's reject this patch due to possible upstream solution as Jeremy
> mentioned.
> Best
> Bartek
> On 19.11.2019 11:15, Jérémy ROSEN wrote:
>
> As a side-note, I am working with upstream to have a better support of (3)
> : https://github.com/systemd/systemd/pull/14059
>
> I am a bit cautious about the new config option because it seems too
> "advanced" for a config option (for me, it's something that should be set
> in a post-image or overlay) but that's open to discussion.
>
> Please wait a little before applying this patch, if that's the way
> buildroot wants to go, so my pull-request above is solved and we might
> backport it to ease our transition.
>
> Cheers
> Jérémy
>
> Le mar. 19 nov. 2019 à 09:40, Thomas Petazzoni <
> thomas.petazzoni at bootlin.com> a écrit :
>
>> Hello,
>>
>> On Sun, 17 Nov 2019 17:00:05 +0100
>> Arnout Vandecappelle <arnout at mind.be> wrote:
>>
>> > > Could something like that be enough ? can we trust "remount RW" ?
>> > > maybe "remount RW" should be renamed "create a RW filesystem" and
>> enable various
>> > > tweaks related to RO vs RW
>> >
>> >  As written above: no.
>> >
>> >  The problem is: we're not a distro.
>>
>> Agreed.
>>
>> > We leave too much freedom for the user to
>> > integrate things in various ways to be able to make assumptions about
>> what is
>> > the right way to do things. So, the only thing we can do is to give a
>> decent
>> > out-of-the-box experience, and let the user figure out how to tweak
>> things -
>> > possibly adding a config option for a common situation that is easily
>> handled in
>> > a generic way. The other thing we can do is to provide documentation
>> about the
>> > proper way to integrate things in different scenarios.
>> >
>> >  I'm starting to agree that this option is maybe not that great.
>>
>> But I would in fact not come to the same conclusion. Having this empty
>> machine-id file is useless and causes problems when the filesystem is
>> R/W. So for the sake of supporting the R/O case (for which we create
>> this empty machine-id file), we make the R/W experience less good.
>>
>> So I'd say that the right approach is to not do too much integration by
>> precisely having the option proposed by Bartosz, with many the tweak
>> that it should default y if rootfs is really, and default disable
>> otherwise, but while still being an option that the user can tweak,
>> because as you rightfully explained, the RW/RO remount option is just a
>> clue, not a definitive answer on whether /etc is writable or not.
>>
>> To me, having this option matches the Buildroot way: we are not a
>> distro, we don't enforce how the system should work, so we provide the
>> appropriate options, while making sure the option has the most sensible
>> default values.
>>
>> Generally speaking, Buildroot kind of supports "out of the box" two use
>> cases:
>>
>>  (1) The root filesystem is completely read-write.
>>
>>  (2) The root filesystem is completely read-only, and all files that need
>>      to be written are stored in tmpfs, and therefore are volatile.
>>
>> I.e, we do not have any explicit support for what is I guess a much
>> more common use case than (2):
>>
>>  (3) The root filesystem is completely read-only, but there is another
>>      read-write partition somewhere that stores the information that can
>>      change but needs to be persistent (user configuration, etc.)
>>
>> Since we don't have explicit support for (3), there is no way we can
>> properly support machine-id and ConditionFirstBoot in the case of (2),
>> because there's nowhere we can store /etc/machine-id.
>>
>> So the best we can do is in the case of (2), default to creating an
>> empty /etc/machine-id, while giving the possibility for the user
>> implementing (3) in its own way, to disable the creation of the empty
>> /etc/machine-id.
>>
>> Best regards,
>>
>> Thomas
>> --
>> Thomas Petazzoni, CTO, Bootlin
>> Embedded Linux and Kernel engineering
>> https://bootlin.com
>>
>
>
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-- 
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*Jérémy ROSEN*
Architecte technique

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