[systemd-devel] Why is systemd-run --scope synchronous?

Simon McVittie smcv at collabora.com
Tue Feb 6 14:28:33 UTC 2018

On Tue, 06 Feb 2018 at 13:09:26 +0100, worz wrote:
> I am not sure why things are different. I also
> notice the difference is that in case of --scope, the service manager is
> not really the parent process, and it's just that systemd-run creates a 
> transient scope and places the process inside it, which is ok, but not sure
> why it is different than running it as a service, or even running the process
> in the scope unit as a child of the service manager.

If I understand correctly, that's exactly the purpose of scope units:
they allow processes that are not a child of the service manager to be
made visible to the service manager as a unit.

For instance, when Flatpak is run on a system with `systemd --user`,
it puts each instance of a Flatpak app in a scope, even though those
processes need to be children of the Flatpak process so they can inherit
various fds and environment variables from it.

(One notable example of a fd that might be inherited by child processes
is "the controlling terminal".)


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