[lxc-users] Containers on linux-4.8-rc1 sometimes(?) requiring "cgmanager -m name=systemd" (bisected, but is it a bug?)

[Eric W. Biederman]

Adam Richter <adamrichter4 at gmail.com> writes:

> Hello, Eric.
>
> Thank you for your prompt response to my posting.
>
> If you think that the new lxc behavior is acceptable, I am OK with it
> too. I just wanted to let you know because I thought that there was
> perhaps a ~30% chance that you might see it as indicating a more
> consequential problem.

Thank you for that.  In practice this comes closer than I would like to
the kernel's no regressions rule.

> I emailed lxc-users instead of lxc-devel to see if if I could
> determine that this was not a bug without needing to escalate to
> lxc-devel.  Also in an effort to err on the side of trying to minimize
> annoyance, I bcc'ed you and Tejun instead of cc'ing you because I
> didn't want effectively to involuntarily subscribe you to what could
> become an ongoing thread.  However, based on your expressed
> preference, I will cc you if I respond further to this thread on
> lxc-users, unless you request otherwise.

Thank you.

> Perhaps, in the future, if I look into control groups and containers
> more, I might investigate your alternative idea, that might not
> require non-systemd host to do anything specific to systemd to run
> systemd guests, reducing the specialness of the real host environment,
> thereby perhaps slightly increasing the set of configurations that can
> be tested with nested containers instead of VM's and reducing barriers
> to other init systems doing whatever systemd does that currently needs
> that bit of host configuration.

How to handle these hierarchy mismatches is part of a very slow moving
and important conversation going on with how cgroup hierarchies will be
treated in the future.  The cgroup2 filesystem and much of the work is
based on the assumption that people will want exactly one hierarchy.
Given containers that run Centos 7 and similar distributions today that
will be an interesting discussion.

Eric