Re: How to undo a merged-user installation?

[jnqnfe@gmail.com]

On Tue, 2020-02-18 at 17:35 +0000, jnqnfe@gmail.com wrote:
> On Tue, 2020-02-18 at 17:58 +0100, Svante Signell wrote:
> > Hello,
> > 
> > I recently installed Debian/bullseye/sid in a VM from a snapshot.
> > After running
> > that image I realized the I got a merged-user installation.
> > 
> > As for now I have:
> > bin -> usr/bin
> > lib -> usr/lib
> > lib32 -> usr/lib32
> > lib64 -> usr/lib64
> > libx32 -> usr/libx32
> > sbin -> usr/sbin
> > 
> > Is there some way to achieve a non-merged-user system from the
> > current
> > situation? 
> > 
> > The Debian Installer does not seem to have an option for a non-
> > merged-user
> > installation. Is that true?
> > 
> > Thank you for your time!
> 
> As I understand it (I somehow only became aware of it days ago) a
> move
> to merged usr has been a move planned for Debian since ~2014 and all
> more recent installers implement it by default. I would not expect
> any
> available switch in the installer to avoid it (why add complexity to
> support the older layout that surely no-one needs?).
> 
> I have to ask, why are you determined to spend effort reversing the
> change?
> 
> While merging is of course trivial, un-merging is most certainly not.
> The easiest methods that occur to me would be to either:
>  a) if you have access to an older version of the installer, do a
> fresh
> install with that (then of course upgrade).
>  b) make sure the usrmerge package is not installed; manually switch
> the symlinks back to actual directories; then ask apt/aptitude to do
> a
> reinstall of every package on your system.
> 
> Of course I cannot give you any guarantee that the above procedure
> will
> actually be successful. Proceed at your own risk. :)

edit: what on earth am I thinking, solution B isn't going to be
sufficient unless DPKG is brilliant enough to remove things from the
old locations; you're ineviatably going to end up still with the merged
copies of things floating about in the merged-to directories...

to solve that, you cannot exactly just delete the directories before
asking apt to reinstall because then you'll likely have broken apt.
perhaps after an all-package reinstall you can then purge all files
from the merged-to directories that exist in the now unmerged
directories (then do a second round of all-packages reinstall, or find
a means of checking for packages with missing files to reinstall, to be
safe).

as I say, non-trivial and proceed at your own risk...