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Bug#1027429: mmdebstrap: unshare backend not working

From	Johannes Schauer Marin Rodrigues <josch@debian.org>
Newsgroups	linux.debian.bugs.dist
Subject	Bug#1027429: mmdebstrap: unshare backend not working
Date	2022-12-31 17:50 +0100
Message-ID	<FINdw-eD8L-11@gated-at.bofh.it> (permalink)
References	<FIIGR-eAfw-3@gated-at.bofh.it> <FIJMB-eB8R-11@gated-at.bofh.it> <FIM7L-eCve-1@gated-at.bofh.it> <FIIGR-eAfw-3@gated-at.bofh.it> <FIM7L-eCve-1@gated-at.bofh.it>
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Quoting Andrea Pappacoda (2022-12-31 16:29:00)
> Il giorno sab 31 dic 2022 alle 14:00:54 +01:00:00, Johannes Schauer 
> Marin Rodrigues <josch@debian.org> ha scritto:
> > Do you have a valid /etc/subuid? Mine says (josch is my username):
> > 
> > josch:100000:65536
> 
> Nope, both /etc/subuid and subgid are empty on my system. They aren't 
> on my other one that doesn't use systemd-homed, so maybe these are 
> populated by useradd(8)?

That is correct.

> It seems that systemd's issue tracker has a relevant RFE still unresolved,
> <https://github.com/systemd/systemd/issues/13717>;

"Uh. The concept of subuids/subgids is just wrong, i am sorry. Static files in
/etc is even worse."

Sounds like that issue will remain open.

> maybe it makes sense to somewhat mention it in sbuild's manual page, it might
> not be obvious for users that don't know much about unshare and user
> namespaces.

But is a user not consciously making the choice for systemd-homed instead of
using the Debian defaults and should thus be prepared for the consequences of
that non-default choice? Recommending to add stuff to /etc/subuid and
/etc/subgid also doesn't sound like the correct choice if the upstream
maintainer of systemd-homed doesn't think it a good idea.

> In any case, manually putting tachi:100000:65536 in subuid and subgid solved
> the issue. Thanks!

Nice!

> > How could the error message be improved?
> I'm not sure, I really don't know much about this subject :/

In your case, since the files were empty, the line you put in was the correct
solution. In other cases, where there is already content in these files, adding
a new entry is a bit more involved, as the offsets have to be computed
correctly. The reliable way to do it, is to use useradd but that is obviously
not a solution for systemd-homed users.

> > The error message in sbuild could certainly be improved. Could you try out
> > the following patch:
> Thanks, but I really don't have time know to apply it. Guess I'll let you
> know next year ;)

In my timezone this year only has six hours left, so fair enough. ;)

Thanks!

cheers, josch

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Thread

Bug#1027429: mmdebstrap: unshare backend not working Andrea Pappacoda <andrea@pappacoda.it> - 2022-12-31 13:00 +0100
  Bug#1027429: mmdebstrap: unshare backend not working Johannes Schauer Marin Rodrigues <josch@debian.org> - 2022-12-31 14:10 +0100
    Bug#1027429: mmdebstrap: unshare backend not working Andrea Pappacoda <andrea@pappacoda.it> - 2022-12-31 16:40 +0100
      Bug#1027429: mmdebstrap: unshare backend not working Johannes Schauer Marin Rodrigues <josch@debian.org> - 2022-12-31 17:50 +0100

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