Re: merged /usr vs. symlink farms

[Wouter Verhelst <wouter@debian.org>]

On Mon, Aug 23, 2021 at 08:23:50AM -0700, Russ Allbery wrote:
> Luca Boccassi <bluca@debian.org> writes:
> 
> > Thank you - it has been brought up in this thread as an example of a
> > valid setup, so if it is not, I think it could be good to be extra clear
> > in the policy? How about the following:
> 
> If we tried to document every random bit of buggy packaging behavior
> anyone thought of in Policy, Policy would become unwieldy, so I want to
> verify here that someone really thought having one package containing a
> file in /bin and another package containing the same file in /usr/bin was
> was a reasonable thing to do (as opposed to accidental).  Are there
> packages in the archive like this?  Or could you point me at the message
> in the thread that said this was non-buggy?  I think I missed it.

The problem here is also that if there are two packages like that, on an
usrmerge system, we would not know this is happening.

Let's say there's a package "foo" which installs /usr/bin/foo, and an
package "binfoo" which installs "/bin/foo". In the current situation,
dpkg would not know that the two files are equivalent, and would happily
overwrite /usr/bin/foo with /bin/foo if "binfoo" was installed after
"foo".

Then when the user notices the "foo" program is not doing what they
believe it should be doing and runs "reportbug /usr/bin/foo", reportbug
will file the bug against the package "foo" rather than the package
"binfoo" which is the actual package whose binary they are trying to
use.

In contrast, if foo and binfoo both install "/bin/foo" (or both install
"/usr/bin/foo", either way works), then dpkg will complain at
installation time that one of the two packages tries to overwrite a file
from the other and refuse to continue.

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