On 1/10/22 23:53, Chris Murphy wrote:
On Mon, Jan 10, 2022 at 9:20 AM David Cantrell <dcantrell@xxxxxxxxxx> wrote:
On Wed, Dec 29, 2021 at 10:01:57AM -0500, Ben Cotton wrote:
https://fedoraproject.org/wiki/Changes/RelocateRPMToUsr
== Summary ==
Currently, the RPM databases is located in `/var`. Let's move it to
`/usr`. The move is already under way in rpm-ostree-based
installations, and in (open)SUSE.
[snip]
Moving the RPM database to /usr feels incorrect to me, but we should move it
to gain the improvements as noted in the feature proposal.
Going back to the original discussions on moving rpmdb...
Preferred is a new top-level location in /usr, .e.g /usr/sysimage/rpm.
Next is "least worst" in /usr/lib/sysimage/rpm
http://lists.rpm.org/pipermail/rpm-maint/2017-October/006764.html
http://lists.rpm.org/pipermail/rpm-maint/2017-October/006722.html
And the convergence was on /usr/lib/sysimage/rpm
http://lists.rpm.org/pipermail/rpm-maint/2017-October/006785.html
I don't see how /state solves the problem, rather than just
rearranging the chairs.
The problem with /usr/something is that the rpmdb is not specific to
/usr contents at all, and unlike any other content in there, so putting
it there just *feels so wrong*. That's what /state or /sysimage or, as
we now have, /var supposedly solves.
I thought I'd suggested something at / level back then (in
https://lists.rpm.org/pipermail/rpm-maint/2017-October/006697.html
and/or
https://lists.rpm.org/pipermail/rpm-maint/2017-October/006699.html) but
seems like memory is failing me :) Maybe I thought it would seem too
outrageous to FHS believers to bother.
The point was though, that the rpmdb is not at all the only data of this
kind and so having a dedicated home makes sense.
For many practical purposes it's probably just rearranging the chairs,
but a separate top-level directory describing the *system* state seems
instinctively *much* more correct solution to it than stuffing it
somewhere deep inside a loosely related fs.
Just FWIW, I would quit my whining about this right there if it went to
a new toplevel directory instead because it just *feels* right unlike /usr.
Numerous followups have noted the requirement that /usr contain read-only
content, that it be shareable across hosts, and similar concepts. While this
may or may not doable now like we could in the past, the bigger thing to me is
around the understanding of what /usr contains. It is generally understood
that /usr contains [most of] the installed system. What I think is a bigger
requirement or expection now is that one can tar up /usr and transport it to
another system or virtual machine or container and expect that it will
_probably_ work maybe with a bit of tinkering. This is a really valuable
thing to have for developers. Moving the RPM database to this tree adds a
component that is unnecessary and sort of out of place.
Should /usr be independently portable? And is that with a version
matched /opt, or can there be mix and match revisions of /usr and
/opt?
If /usr is to be truly portable and have e.g. 'rpm query, verify,
remove, reinstall' work as expected, you need the metadata (the
database) representing its state to always come along for the ride.
Either the database is already in /usr, or you have to make sure /usr
and /state are inseparable.
If /usr and /state are inseparable, and if rpm can also describe
anything in /etc or /var or /opt, then all or part of those
directories are also inseparable from /state. And thus /usr. So I
think /state doesn't help.
For one, /state (or whatever toplevel directory) allows for the fact
that there are write-operations to rpmdb that do not touch any external
files while maintaining read-only /usr. Such as rpmdb --rebuilddb, or
rpm --import.
And like mentioned in the original discussion and now here, although the
discussion is on rpmdb, it's not the only data of this kind.
To what degree do rpm and dnf intend to touch locations outside of
/usr *and care* about tracking those changes?
I don't understand the question. Rpm tracks and cares about all content
it knows about equally, regardless of the path. /usr is NOT special in
any way to rpm, it's just that most of *distro* content ends up in there
but a huge number of packages have content spread across /etc too.
I think rpm can't remain
static for all time. It either needs to become aware of multiple root
trees, and even mix and match top-level directories to create variable
roots. And possibly even manage these things. Or it needs to constrain
its reach to /usr and /opt. Whether /usr and /opt are tied together,
or can be mix and match with their own rpmdb's, I have no strong
opinion on.
Oh, multiple rpmdbs. It's a while since that last turned up. It gets
tossed around as a solution but to me it looks like it brings more
problems than it solves.
- Panu -
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