[systemd-devel] Please clarify osVersion in ELF package metadata

[Luca Boccassi]

On Mon, 17 Jun 2024 at 17:45, Benjamin Drung <bdrung at ubuntu.com> wrote:
>
> On Mon, 2024-06-17 at 14:54 +0100, Luca Boccassi wrote:
> > On Mon, 17 Jun 2024 at 14:45, Benjamin Drung <bdrung at ubuntu.com> wrote:
> > >
> > > Hi,
> > >
> > > Ubuntu started to implement the ELF package metadata spec. It encodes
> > > the VERSION_ID from os-release in the osVersion field. Using VERSION_ID
> > > was objected to because the version is only set in stone once the
> > > release is done. It could change during the development cycle. See
> > > https://lists.ubuntu.com/archives/ubuntu-devel/2024-June/043027.html
> > > and https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/2069599
> > >
> > > The proposal is to use VERSION_CODENAME from os-release instead.
> > >
> > > To me it is not clear enough what is the best approach regarding the
> > > spec https://systemd.io/ELF_PACKAGE_METADATA/ here.
> > >
> > > The key description says "typically"? So could we just use
> > > VERSION_CODENAME for osVersion?
> > >
> > > Or should be use a different key like osVersionCodename to allow third-
> > > party users to still use VERSION_ID for osVersion? In that case
> > > osVersionCodename should probably added to the well-known keys.
> > >
> > > What's your take on it?
> >
> > Hi,
> >
> > I replied on ubuntu-devel but it's moderated, so the message didn't
> > make it through and is waiting for approval.
> >
> > The gist of it is that this is supposed to be machine readable, and be
> > what is commonly understood as the version, which for the next ubuntu
> > version would be 23.10.
> >
> > Given it's sourced from os-release, which is sourced from base-files,
> > ideally you'd do an archive-wide rebuild once it is finalized (that
> > also gives you builds with newer compiler hardening and other
> > niceties). If that's not possible or not wanted, simply omit the
> > osVersion field. Parsers need to expect that to be optional, in order
> > to avoid breaking on rolling release distros like Arch that do not
> > have a version.
>
> From that perspective Debian and Ubuntu are semi-rolling releases:
> Packages are copied over from one release to another. As long as there
> is no new upload happening for the package between two release, the
> identical binary package will be shipped. So osVersion would still be
> unchanged. So osVersion indicated which os version the package was
> introduced but not on which release it is running on. Do you suggest to
> omit osVersion due to that?

Yes. In fact, in the Debian debhelper I do not set osVersion either.

> My initial question targets a different problem: The version number is
> finalized (set in stone) on release date. Ubuntu was released on time
> except for one case. In such case where we need more time and delay the
> release, we won't have time to start an archive wide rebuild of all
> package just to correct osVersion in the ELF objects. On the other hand
> the version codename is set in stone when the archive for that release
> is opened. That's why it was suggested to use the version codename
> instead of the version ID.

Codenames are not great for this purpose, one issue is that not being
numeric, you cannot do version comparison on them, for example.