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

Bartosz Bilas b.bilas at grinn-global.com
Mon Feb 3 18:28:16 UTC 2020


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 <mailto:thomas.petazzoni at bootlin.com>> a 
> écrit :
>
>     Hello,
>
>     On Sun, 17 Nov 2019 17:00:05 +0100
>     Arnout Vandecappelle <arnout at mind.be <mailto: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
>
>
>
> -- 
> SMILE <http://www.smile.eu/>
>
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>
> 	
> *Jérémy ROSEN*
> Architecte technique
>
> email jeremy.rosen at smile.fr <mailto:jeremy.rosen at smile.fr>
> phone  +33 6 88 25 87 42
> url http://www.smile.eu <http://www.smile.eu/>
>
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