Bug#930684: pbuilder: creation of build env fails when run inside Docker container

[Tobias Junghans <tobydox@veyon.io>]

Am Dienstag, 18. Juni 2019, 21:10:53 CEST schrieb Thorsten Glaser:
> Tobias Junghans dixit:
> >I tried to upgrade my Docker-based pbuilder containers from stretch to
> 
> Erm… why do you use chroots inside of chroots? That’s… tricky.

Simple because we use Gitlab Runners with the builtin Docker Executor 
(https://docs.gitlab.com/runner/executors/docker.html) for running all kinds 
of jobs in a generic manner. Depending on the project individual pre-built 
Docker images (specified in the CI config) providing the desired build tools 
and toolchains are used. The jobs for building Debian packages use a Docker 
container with Debian and pbuilder installed.

This used to work for years but for Buster-based containers (i.e. pbuilder and 
debootstrap from Buster) it doesn't any longer.


> >mount: failed to read mtab: No such file or directory
> 
> This might be a container issue.

The mounts are fine before running pbuilder/debootstrap. Afterwards proc is 
not mounted even in the Docker container. The state of the container and its 
mounts shouldn't change when running debootstrap. I also saw Docker/container-
related changes between 1.0.89 (stretch) and buster (1.0.114) which likely 
cause the misbehaviour:

https://salsa.debian.org/installer-team/debootstrap/commit/
5a0f16664066b24c42c074643a4ca178890d7af7
https://salsa.debian.org/installer-team/debootstrap/commit/
0962af1527a1ba0e996a0b442b159b4dbf164988
https://salsa.debian.org/installer-team/debootstrap/commit/
1e7549c57c0f15816c89c4f243051785ca383be9

> >mount: /proc: mount(2) system call failed: Too many levels of symbolic
> >links.
> Check if /proc outside of pbuilder but inside the container is right.

/proc in the container is fine, see first output of "cat /proc/mounts
" in by original bug report.
 
> But with {cow|p}builder --login --save-after-login you can
> upgrade the base to buster inside pbuilder.

It's not about the pbuilder environment itself but the Docker container used 
for invoking pbuilder/debootstrap. Using a stretch-based Docker container and 
debootstrapping Buster works fine.

Thanks and best regards

Tobias