[systemd-devel] Dropping split-usr/unmerged-usr support

[Mike Gilbert]

On Tue, Apr 5, 2022 at 4:07 PM Luca Boccassi <luca.boccassi at gmail.com> wrote:
>
> Hi,
>
> As part of our spring cleaning effort, we are considering when to drop
> support for split/unmerged-usr filesystem layouts.
>
> A build-time warning was added last year:
>
> https://github.com/systemd/systemd/commit/9afd5e7b975e8051c011ff9c07c95e80bd954469
>
> We are now adding a runtime taint as well.
>
> Which distributions are left running with systemd on a split/unmerged-
> usr system?

Gentoo still supports having /{bin,sbin,lib} and /usr/{bin,sbin,lib}
as separate directories. We do not support officially booting without
/usr mounted (via initramfs), but some users do it anyway.

We are not likely to require merging of / and /usr for the foreseeable
future. We are a "rolling release" distro and basically never require
our users to re-install, which makes large file system migrations
difficult. Also, many of our users would resist any attempt to force
merged-/usr on them.

I think it would be ok if systemd drops support for installing itself
in /lib/systemd; we would just move everything under /usr/lib/systemd,
and possibly set up some symlinks in /lib/systemd for the transition.

We will still need to keep /bin and /sbin in PATH, and we can't assume
that all binaries reside in /usr/bin.