[systemd-devel] Adding controllers

Lennart Poettering lennart at poettering.net
Thu Mar 2 17:20:18 UTC 2017

On Thu, 02.03.17 15:28, Bhasker C V (bhasker at unixindia.com) wrote:
> [Manager]
> JoinControllers=

JoinControllers= is not what you think it is. It's a system-wide
setting for mount multiple cgroupsv1 controllers into the same
hierarchy. You almost never need that in real-life.

> ---
> From what I can read from the man page, The joincontrollers is a list
> of controllers the systemd unit will "not" join.. Please correct me if
> my understanding is wrong.
> I am however not able to make this systemd-nspawn join freezer controller.
> The only way I am able to achieve this is
> ExecStart=/usr/bin/cgexec -g freezer:/ubuntu /usr/bin/systemd-nspawn
> --keep-unit -jbD /machines/ubuntu
> (of course I use ExecStartPre to create the freezer:/ubuntu)
> But I feel there must be more systemd-native elegant way to do this.
> Please can someone guide me ?

systemd does not support the freezer controller, as it's interface to
userspace is simply broken.

Delegation of controllers to less privileges containers is not safe,
and we don't support that right now either. Sorry.


Lennart Poettering, Red Hat

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