Broken journalctl / broken resolvconf in docker runners

Hi,

in this salsa CI run installation of the package resolvconf fails. (Copying the error in case the logs become unavailable):

Setting up resolvconf (1.79) ...
ln: cannot remove '/etc/resolv.conf': Device or resource busy
dpkg: error processing package resolvconf (--configure):
 subprocess installed post-installation script returned error exit status 1

It seems as though /etc/resolv.conf is marked immutable, which breaks installation.

The second job in question fails due to journalctl returning empty log data, even though there should be:

adt-run [11:12:12]: test compile-time-options: [-----------------------
No journal files were found.

I believe both are errors within the docker image, as when running those tests locally with autopkgtest-virt-qemu they pass.

If it turns out this is a design limitation of docker, I believe this should be prominently documented in the autopkgtest test restrictions (/usr/share/doc/autopkgtest/README.package-tests.*)

changed the description

These are generic restrictions for containers (not just Docker). I can reproduce the error above by basically starting any container on my laptop and running apt update && apt install resolvconf. Containers typically don't have any services running, and hence no systemd to manage services, nor any journald running.

I am not aware of any comprehensive document that would list all restrictiongs of containers on Linux, but I agree that it would be good to have a reminder about that they exists on the Salsa CI README.md. Perhaps you want to take a stab at writing it and submit a Merge Request