How to write startup script for Systemd?

I have 2 graphics cards on my laptop. One is IGP and another discrete. I've written a shell script to to turn off the discrete graphics card. How can I convert it to systemd script to run it at start-up?

547 2 2 gold badges 7 7 silver badges 20 20 bronze badges asked Sep 10, 2012 at 10:01 3,203 3 3 gold badges 17 17 silver badges 8 8 bronze badges

2 Answers 2

There are mainly two approaches to do that:

With script

If you have to run a script, you don't convert it but rather run the script via a systemd service:

Therefore you need two files: the script and the .service file (unit configuration file).
Make sure your script is executable and the first line (the shebang) is #!/bin/sh . Then create the .service file in /etc/systemd/system (a plain text file, let's call it vgaoff.service ).
For example:

  1. the script: /usr/bin/vgaoff
  2. the unit file: /etc/systemd/system/vgaoff.service

Now, edit the unit file. Its content depends on how your script works:

If vgaoff just powers off the gpu, e.g.:

exec blah-blah pwrOFF etc

then the content of vgaoff.service should be:

[Unit] Description=Power-off gpu [Service] Type=oneshot ExecStart=/usr/bin/vgaoff [Install] WantedBy=multi-user.target

If vgaoff is used to power off the GPU and also to power it back on, e.g.:

start() < exec blah-blah pwrOFF etc >stop() < exec blah-blah pwrON etc >case $1 in start|stop) "$1" ;; esac

then the content of vgaoff.service should be:

[Unit] Description=Power-off gpu [Service] Type=oneshot ExecStart=/usr/bin/vgaoff start ExecStop=/usr/bin/vgaoff stop RemainAfterExit=yes [Install] WantedBy=multi-user.target

Without script

For the most trivial cases, you can do without the script and execute a certain command directly:

[Unit] Description=Power-off gpu [Service] Type=oneshot ExecStart=/bin/sh -c "echo OFF > /whatever/vga_pwr_gadget/switch" [Install] WantedBy=multi-user.target

To power off and on:

[Unit] Description=Power-off gpu [Service] Type=oneshot ExecStart=/bin/sh -c "echo OFF > /whatever/vga_pwr_gadget/switch" ExecStop=/bin/sh -c "echo ON > /whatever/vga_pwr_gadget/switch" RemainAfterExit=yes [Install] WantedBy=multi-user.target

Enable the service

Once you're done with the files, enable the service:

systemctl enable vgaoff.service

It will start automatically on next boot. You could even enable and start the service in one go with

systemctl enable --now vgaoff.service

as of systemd v.220 (on older setups you'll have to start it manually).
For more details see systemd.service manual page.

Troubleshooting