[systemd-devel] systemd release agent

[Lennart Poettering]

On Tue, 09.04.13 16:39, Kevin Wilson (wkevils at gmail.com) wrote:

> Hello,
> On Fedora 18, running:
> mount | grep release
> gives:
> cgroup on /sys/fs/cgroup/systemd type cgroup
> (rw,nosuid,nodev,noexec,relatime,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
> 
> I know and have tried cgroup release_agent;
> 
> I also noticed that  notify_on_release is enabled in systemd cgroups:
> cat  /sys/fs/cgroup/systemd/notify_on_release
> gives 1
> (also in the children, user and system cgroups)
> 
> what does /usr/lib/systemd/systemd-cgroups-agent do ? what it is for ?
> What does it do when it is invoked ?

it's how the kernel notifies about cgroups running empty. The kernel
forks the specified binary out. We install a binary there that simply
sends a message on the bus about the cgroup running empty.

It's an awful kernel API, but the only one there is for this.

Lennart

-- 
Lennart Poettering - Red Hat, Inc.