RE: [systemd-devel] Purpose of init.scope

For anyone interested:

https://github.com/systemd/systemd/pull/1116

"This moves PID 1 into a new "init.scope" implicit scope unit in the root

slice. This is necessary since on the unified hierarchy cgroups may

either contain subgroups or processes but not both. PID 1 hence has to

move out of the root cgroup (strictly speaking the root cgroup is the

only one where processes and subgroups are still allowed, but in order

to support containers nicey, we move PID 1 into the new scope in all

cases.) This new unit is also used on legacy hierarchy setups. It's

actually pretty useful on all systems, as it can then be used to filter

journal messages coming from PID 1, and so on."


________________________________________
From: systemd-devel <[email protected]> on behalf of Lennart Poettering <[email protected]>
Sent: Sunday, August 16, 2026 11:02 AM
To: Demi Marie Obenour <[email protected]>
Cc: systemd development <[email protected]>; Linux cgroups development <[email protected]>; Alyssa Ross <[email protected]>
Subject: [EXTERNAL] Re: [systemd-devel] Purpose of init.scope
 
On Mi, 29.07.26 16:13, Demi Marie Obenour ([email protected]) wrote:

> What is the purpose of having PID 1 in init.scope?  Is it functionally
> necessary, or is it solely for consistency with when systemd is
> running in a container or as a user service manager?

PID 1 needs to live somehwere, so that's where we put it. Where else
would you put it?

Lennart

--
Lennart Poettering, Berlin