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dz

Member

Registered: 2013-08-21

Posts: 16

Restart a systemd service without killing its children

I use a user-level systemd service to run a hotkey daemon.  For example, a key to open a terminal or web browser.  These terminals end up being children of the hotkey daemon, and restarting the daemon kills them.  Is there anything I can do to restart the parent process without killing the children?

`ExecReload` is not applicable in this case, and neither is patching the hotkey daemon.

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,293

Re: Restart a systemd service without killing its children

Can you set the hotkey up to disown the process after spawning it?     Maybe:  urxvt && disown

Edit:  Or, are the commands baked into the daemon?

Last edited by ewaller (2016-05-09 20:35:21)

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Wibjarm

Member

Registered: 2012-05-04

Posts: 43

Re: Restart a systemd service without killing its children

What you might want to do is set the hotkey daemon up to use systemd-run to launch things.  That way, the child processes are reparented to your systemd --user instance, and tracked as separate service (or scope) units rather than as part of the hotkey daemon's service.  That should do pretty much what you want.

Last edited by Wibjarm (2016-05-10 01:53:42)

Trilby

Inspector Parrot

Registered: 2011-11-29

Posts: 30,330

Website

Re: Restart a systemd service without killing its children

`man setsid`

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dz

Member

Registered: 2013-08-21

Posts: 16

Re: Restart a systemd service without killing its children

Thanks everyone!  I used `setsid`, although `disown` would probably also work.

Vain

Member

Registered: 2008-10-19

Posts: 179

Website

Re: Restart a systemd service without killing its children

I'm confused. How can a simple `setsid` make the child processes leave the daemon's cgroup? Shouldn't systemd clean/kill the whole cgroup?

From my understanding, you should need to do what Wibjarm suggested.

Which hotkey daemon are you using? How does the actual unit file look like?

Just curious.

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