Bug#1110873: dpkg: DPKG_ROOT documentation unexpectedly mentions instdir

Guillem Jover <[email protected]> writes:

> On Mon, 2025-08-11 at 22:10:34 +0200, Ferenc Wágner wrote:
>
>> "man dpkg" says:
>> 
>>   DPKG_ROOT
>>       [...] When installing packages into a different instdir, dpkg
>>       normally invokes maintainer scripts using chroot(2) and leaves
>>       this variable empty, but if --force-script-chrootless is specified
>>       then the chroot(2) call is skipped and instdir is non-empty.
>> 
>> The above would make more sense to me if the "instdir" reference in the
>> last line was "DPKG_ROOT", so I suspect a typo here.  Please fix the
>> documentation or my confusion.
>
> This would be the directory that is being set when using --instdir,
> which --root ends up setting as well as --admindir.
>
> Perhaps if that read closer to `--instdir` that would have been more
> clear?

Hi Guillem,

What I miss here is when dpkg sets the DPKG_ROOT variable to something
non-empty.  From the text I understand that dpkg sets DPKG_ROOT to the
empty string when --root and --instdir are not set (so "normally").
Furthermore, dpkg also sets DPKG_ROOT to the empty string when --root or
--instdir is set, *unless* --force-script-chrootless is also specified
(because the maintainer scripts are run in a chroot then).  So it would
seem sensible if dpkg set DPKG_ROOT to the value of --instdir (or
--root) if either of them is specified, *and* --force-script-chrootless
is also specified.  But the text does not say that, instead it contrasts
DPKG_ROOT being empty with instdir being non-empty.  This is unexpected,
and I don't even understand instdir in the "Internal environment"
context where this paragraph resides.

I'm not sure I managed to express my difficulty any better now...
-- 
Thanks,
Feri.