Re: merged /usr

[Wouter Verhelst <wouter@debian.org>]

On Mon, Aug 16, 2021 at 04:17:01PM +0200, Marco d'Itri wrote:
> On Aug 16, Wouter Verhelst <wouter@debian.org> wrote:
> > On Fri, Aug 13, 2021 at 07:53:20AM +0200, Marco d'Itri wrote:
> > > Implementations with real /bin /sbin /lib* directories and symlink farms
> > > are not useful because they would negate the major benefits of 
> > > merged-/usr, i.e. the ability of sharing and independently updating 
> > > /usr.
> > In those cases, you would never run dpkg inside the system with the
> > "shared" /usr directory, so for those cases having /bin /sbin /lib* be
> > symlinks or real directories is irrelevant.
> It is not irrelevant because then you would need to update /bin /sbin 
> /lib* on the root file system when a new binary is added to the /usr 
> file system (e.g. in an updated OS image).
> So I do not think that you understand well this use case.

My point is:

There is pushback against having usrmerge as the "default" thing,
because it confuses dpkg. Therefore some people would prefer a solution
that does not require all systems to have /bin etc be symlinks unless
and until the transition is complete.

This pushback however is only relevant for systems where dpkg will run.
If dpkg will not run, then dpkg cannot get confused, and so you *can*
have /bin etc be symlinks and it won't cause problems.

So "this is problematic for a case where dpkg will not run" is
irrelevant, as there you can do what you want and dpkg won't get
confused at all.

> > The point of having /bin etc not be a symlink is *to stop confusing
> > dpkg*.
> This is a legitimate but very minor goal which could also be achieved 
> by changing dpkg.

Yes; but according to the dpkg maintainer, "changing dpkg" will take
much effort that may cause corner case bugs (including files
disappearing), and it would be easier (as in, faster and less likely to
cause problems) to try to do this in some other way. Perhaps he's wrong
at this (I don't know), but I haven't seen anyone take his concerns
seriously, and/or even try to come up with solutions to the concerns
that are raised.

Putting your hands in your ears and saying lalala it's not true is not
helping anyone.

(of course it might be that you have tried to do this and I've just
missed it, in which case just point me to the relevant bug)

-- 
     w@uter.{be,co.za}
wouter@{grep.be,fosdem.org,debian.org}