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Bug 843818 - merged usr profiles for systemd
Summary: merged usr profiles for systemd
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: Profiles (show other bugs)
Hardware: All Linux
: Normal normal (vote)
Assignee: Gentoo systemd Team
Depends on:
Blocks: usrmerge, usrmerge-fixes future-profile
  Show dependency tree
Reported: 2022-05-11 20:57 UTC by Georgy Yakovlev
Modified: 2022-09-06 07:48 UTC (History)
4 users (show)

See Also:
Package list:
Runtime testing required: ---


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Description Georgy Yakovlev archtester gentoo-dev 2022-05-11 20:57:21 UTC
Discussion and tracking bug for merged usr problems and solutions
Comment 1 Georgy Yakovlev archtester gentoo-dev 2022-05-11 20:59:18 UTC
dumping some info from IRC discussion:

<@floppym> Someone wrote a script to migrate Gentoo systems to merged-/usr. Does anyone remember where that is?
<@gyakovlev> floppym:
<@gyakovlev> dracut actuall has this =)
<@gyakovlev> I think fedora used it to migrate existing systems in an early phase where root is mounted but not pivoted to.
<@gyakovlev> but ofc it would not work for gentoo
<@gyakovlev> with the amounts of custom stuff users do to their systems.
<@floppym> gyakovlev: Thanks!
<+sam_> oh nice!!
<@floppym> I'm really tempted to require merged-/usr to run systemd on Gentoo within the next couple of releases.
<@floppym> So I will probably start working on new set of systemd profiles.
<@gyakovlev> I've been running that kind of system for a long time so far.
<@gyakovlev> it's mostly ok.
<@gyakovlev> kernel eclasses are still broken tho
<@floppym> How so?
<+sam_> I migrated my system on the weekend and it's been fine so far
<@gyakovlev> those create incorrect symlink
<@gyakovlev> /usr/lib/modules/<>/build
<@floppym> Hmm.
<@gyakovlev> points to incorrect number of ../../src/linux
<@gyakovlev> so you can't build 3rd party modules
<+sam_> sounds easy to fix
<@gyakovlev> sam_: well maybe, but I got tried of hunting this
<@floppym> Well, relative symlinks don't play well with directory symlinks.
<@gyakovlev> something somethere uses realpath
<@gyakovlev> so it resolves with /usr part
<+sam_> interestingly I didn't hit this with zfs when I upgraded kernel yday
<@gyakovlev> but expects /lib/modules path
<@gyakovlev> zfs is smarter =)
<@floppym> /lib/modules/x/build and /usr/lib/modules/x/build cannot possibly point the same place with a relative symlink.
<@gyakovlev> that one is not affected
<@gyakovlev> pure KBUILD packages are affected
<+sam_> ahhh
<@gyakovlev> maybe doing absolute symlink is a solution?
<@gyakovlev> idk
<@floppym> Yes, unfortunately I think that's the only reliable solution.
<@floppym> And it doesn't work if SYSROOT != /
<@floppym> I'm not sure how much of the kenrnel ebuild infra works when cross-compiling anyway.
<@gyakovlev> ok I'm starting to remember (sorry just had coffee)
<@gyakovlev> I think only dist-kernels are broken
<@gyakovlev> because those assume /lib
<@gyakovlev> and install incorrect relative symlink
<@gyakovlev> I think make_install style gentoo-sources resolve fine.
<@gyakovlev> rwxrwxrwx  1 root root     38 Apr 26 17:00 source -> ../../../usr/src/linux-5.15.35-talos64
<@gyakovlev> ^ that is broken symlink if viewed from /lib/modules/5.15.35-talos64
<@gyakovlev> and is broken from /usr/lib/modules/5.15.35-talos64
<+sam_> weird
<+sam_> ah I see it now
<+sam_> lrwxrwxrwx  1 root root      51 May  9 19:32 build -> ../../../usr/src/linux-5.15.38-gentoo-dist-hardened
<+sam_> lrwxrwxrwx  1 root root      51 May  9 19:32 source -> ../../../usr/src/linux-5.15.38-gentoo-dist-hardened
<@gyakovlev> yeah it should have either extra ../
<@gyakovlev> or no usr/ part
<@gyakovlev> I think we talked about this before and agreed that split-usr for dist-kernels is most obvious solution
<@gyakovlev> the flag I mean
<@floppym> Another possible solution would be to create a symlink /src -> usr/src.
-*- gyakovlev hears FHS crowd wooo-ing
<@floppym> Then a relative symlink ../../src/linux would work from either location.
<+sam_> I'd prefer USE=split-usr or something I think.
<@gyakovlev> split-usr is most obvious and discoverable way indeed.
<@gyakovlev> or some autodetection magic
<@floppym> Autodetection magic is bad.
<@floppym> Would much rather utilize the USE flag.
<@gyakovlev> yeah it exists for a reason and hundreds of packages use it
<@gyakovlev> I'm still in semi-amoeba mode but will try to handle it from dist-kernel side
<@gyakovlev> just keep in mind this before new profiles, that'd be a blocker =)
<@gyakovlev> btw I also built merged usr stages locally
<+sam_> oh nice
<@gyakovlev> works fine
<+sam_> i think jpds hit some issues with doing that
<+sam_> do speak to him but should be fixable
<@gyakovlev> another thing:
<@gyakovlev> UNINSTALL_IGNORE="${UNINSTALL_IGNORE} /bin /sbin /usr/sbin /lib /lib64"
<@gyakovlev> this is needed in make.conf (or profiles)
<@gyakovlev> otherwise portage would be bitching about symlinks
<@gyakovlev> also some compressors (pigz lbzip2) have USE=symlink flag
<@gyakovlev> this will have to be masked
<@gyakovlev> those make symlink in usr like pigz -> gzip
<@gyakovlev> since /usr/bin comes 1st in order in path it uses pigz by default
<@gyakovlev> but it will not work for merged usr ofc
Comment 2 Mike Gilbert gentoo-dev 2022-09-03 16:05:16 UTC
merged-usr profiles have been added.