Bug#831691: Please use lxc.haltsignal = SIGRTMIN+3 for systemd containers

[Michael Biebl]

Package: lxc
Version: 1:2.0.3-1
Severity: normal

Hi,

he had an interesting discussion today on #pkg-systemd IRC about what
modifications are currently done for LXC containers to work properly
with systemd. Ideally we'd like to make a default systemd installation work
ootb.

Atm, the Debian template hooks up
/etc/systemd/system/sigpwr.target -> /lib/systemd/system/halt.target.

At some point, Martin added a workaround to the systemd package [1].

Systemd upstream is pretty clear though, that (mis)using SIGPWR to
initiate an ordered shutdown is not the preferred way under systemd [2].
If the container manager sends SIGRTMIN+3 to the init process following
the container spec [3], then systemd will shut down nicely.

I therefor suggest, that lxc should use haltsignal = SIGRTMIN+3 for
systemd based containers.

I would set that in the container config file during lxc-create if the
template is for a systemd-based distro.

Regards,
Michael

[1] https://anonscm.debian.org/cgit/pkg-systemd/systemd.git/commit/?id=44c3369f9
[2] https://lists.freedesktop.org/archives/systemd-devel/2016-July/037166.html
[3] https://www.freedesktop.org/wiki/Software/systemd/ContainerInterface/
-- System Information:
Debian Release: stretch/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'unstable'), (200, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.6.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)