Debian 11 Bullseye is the last Debian release that supports the non-merged-usr layout.
It is therefore foreseeable that Devuan 4 Chimaera will also be.

Official Debian information:

The historical justifications for the filesystem layout with /bin,
/sbin, and /lib directories separate from their equivalents under /usr
no longer apply today; see the Freedesktop.org summary. Debian bullseye
will be the last Debian release that supports the non-merged-usr layout;
for systems with a legacy layout that have been upgraded without a
reinstall, the usrmerge package exists to do the conversion if desired.

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=841666

The Technical Committee resolves that Debian 'bookworm' should
support only the merged-usr root filesystem layout, dropping support
for the non-merged-usr layout.
Until after the release of 'bullseye', any implementation of this
resolution must be done in the 'experimental' distribution, or
otherwise kept out of the critical paths for the release of
'bullseye'.

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=978636
     En viernes, 5 de noviembre de 2021 15:44:21 CET, Martin Steigerwald <martin@???> escribió:  

Hi Svante.

No need to Cc me. I am subscribed. (I know there are different habits, so
just a friendly information.)

Svante Signell - 05.11.21, 11:26:52 CET:
> On Fri, 2021-11-05 at 10:52 +0100, Martin Steigerwald wrote:
> > Debian 11 defaults to usr merge. So the installed system used usr
> > merge.
> >
> > I suppose Devuan is compatible and will remain compatible with that?
> > I think it would be necessary as well some users may migrate from
> > buster. Or one would have to find a way to undo the merge, but this
> > I think is quite error prone.
>
> Devuan defaults to non-merged-/usr as far as I know. You can always
> install with merged-/usr on Devuan too using the expert install
> option. (Personally I prefer non-merged-/usr remains to be the
> default.)

Yeah… I always install Devuan them without merged-/usr.

> > I like to avoid breaking the server VM by undoing usr merge, even
> > tough I prefer systems without usr merge. It is easy to do with
> > systems where I can use a Devuan ISO for installation, but for this
> > system I had the Debian Netinstall ISO and it is what it is.
>
> You can use the dpkg-fsys-usrunmess, with a dpkg release later than or
> equal to 1.20.6, see https://wiki.debian.org/Teams/Dpkg/MergedUsr
>
> "For already installed systems (since dpkg 1.20.6) you can also use
> the dpkg-fsys-usrunmess program to revert the breakage from these
> systems (but beware that it should not be used in systemd's emergency
> mode)."
>
> (I've used that script on two Debian installations successfully
> already.)

Splendid. Thanks a lot for this.

I hesitated, not wanting to cause any further hassle for the admins of
the virtualization infrastructure the server VM runs on, but it indeed
worked.

It appears that… there is… some… discussion about the merged-/usr
approach currently taken in Debian. What a mass.

Happy I could undo it, although I am in awe for the developer of dpkg-
fsys-usrunmess and it feels like I have used a magic wand of some kind.

Best,
--
Martin


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