How to handle tmpfiles.d in non-systemd environments

[Michael Hudson-Doyle]

On Mon, 17 Feb 2020 at 21:34, Christian Ehrhardt <
christian.ehrhardt at canonical.com> wrote:

> Hi,
> There is a bug [1] showcasing an issue failing in a docker container as
> tmpfiles.d there does nothing.
>
> On 6th of December I already wrote to ubuntu-server as part of my daily
> bug duties and subscribed people to the bug. Not much happened since then,
> a few small IRC exchanges and the Debian init system GR was resolved, but
> other than that I didn't hear anything else on the topic.
>
> This class of issues we should IMHO solve/ignore/handle in a general and
> not package specific fashion.
>
> I was wondering if anyone on the core-system or systemd side of things has
> already thought/decided on that class of issues and could chime in on the
> bug.
>
> To everyone - have you seen similar bugs that we should Dup' together in
> regard to this?
>
> [1]: https://bugs.launchpad.net/ubuntu/+source/haproxy/+bug/1855140
>

Fun.

On the face of it, the package is buggy. tmpfiles configs are processed by
systemd, the package depends on the tmpfiles config being processed -> it
should Depend: on systemd. This is not a path forward to having it work in
a docker container though.

One way to make this work might be this:

 1. have src:systemd make a systemd-tmpfiles binary package that just ships
systemd-tmpfiles (upstream has made commitments that systemd-tmpfiles does
not depend on systemd running:
https://lists.debian.org/debian-devel/2019/12/msg00060.html).

 2. Have any package that ship tmpfiles configs depend on this new package
and invoke systemd-tmpfiles in postinst (debhelper / dh_installsystemd does
in fact arrange for systemd-tmpfiles to be invoked in postinst but only
if /run/systemd/system exists, so we'd change that to be unconditional and
get something to add systemd-tmpfiles to misc:Depends).

This is a bit sketchy because nothing will process the tmpfiles fragments
when the container starts, but /run and /tmp and just regular directories
in a docker container (by default anyway) so it might just work (tm).

We should probably coordinate this with Debian. The recent thread
"opentmpfiles & opensysusers, and its use in the Debian policy" is somewhat
related, maybe I should fork a thread off that.

Cheers,
mwh
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