[SOLVED] Run systemd service when AC power is connected

jobach · 2016-04-24 10:59:33

I have a service (say foo.service), of type simple (or forking, for that matter).

I wan't this service to be started every time when my notebook is connected to the power supply, and to be stopped again once it goes back to battery mode.

I know of ConditionACPower=, but this only checks once on the startup of the unit if the power is connected, and does not help triggering the unit in the first place.

Is there a way to achieve this? If not using systemd, then at least in some other way (e.g. calling a specific executable on AC Power events)?

Last edited by jobach (2016-04-24 23:50:47)

frank604 · 2016-04-24 18:33:03

This sounds like an xy problem. How about you detail what you are trying to accomplish and why? Perhaps we can set you in a better direction?

ewaller · 2016-04-24 18:41:25

https://wiki.archlinux.org/index.php/acpid

jobach · 2016-04-24 23:05:05

To specify my problem:

I'm using the i3 window manager, and am expirencing some problems with tearing (see https://wiki.archlinux.org/index.php/I3#Tearing). As the wiki page suggests, Compton helps with that. However, compton increases my CPU load (not much admittedly, but it bugged me anyway). So I only wan't it to run when the power supply is connected.

My solution (using acpid)

I now have acpid start a systemd target I created, like this:

/etc/acpi/handler.sh
----------------------------
#!/bin/bash
[...]
case "$4" in
    00000000)
        logger 'AC unpluged'
        systemctl stop ac-power.target
        ;;
    00000001)
        logger 'AC pluged'
        systemctl start ac-power.target
        ;;
    *)
        logger "Don't know what to do: $4"
        ;;
esac
[...]

The target looks like this:

/etc/systemd/system/ac-power.target
---------------------------------------------------
[Unit]
Description=AC-only services

And the compton-services:

/etc/systemd/system/compton.service
[Unit]
Description=Compton - a compositor for X11
PartOf=ac-power.target

[Service]
Environment="DISPLAY=:0"
User=jobach
ExecStart=/usr/bin/compton [...]

[Install]
WantedBy=ac-power.target

The PartOf= is needed, so the service get's stopped once the targret is stopped (StopWhenUnneeded= might also work).

Last edited by jobach (2016-04-24 23:07:33)

ewaller · 2016-04-24 23:40:07

So, is it solved? If so, please prepend [SOLVED] to your thread title. Thanks.

frank604 · 2016-04-25 20:34:14

Great to hear acpid has solved this for you. A method without acpid could be to utilize udev rules to run a script to start compton when ac is detected and kill compton when ac is unplugged.

Arch Linux

#1 2016-04-24 10:59:33