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

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1 Answer 1

up vote 55 down vote accepted

There are mainly two approaches to do that:

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

To power off:

[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 & 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

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

systemctl enable vgaoff.service

It should start automatically after rebooting the machine.


For more details see systemd.service man page.

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Thanks for detailed answer. The script contains one command "echo OFF > /sys/kernel/debug/vgaswitcheroo/switch" –  Sharique Sep 11 '12 at 10:04
    
it fails with following message vgaoff.service - Power-off gpu Loaded: loaded (/usr/lib/systemd/system/vgaoff.service; enabled) Active: failed (Result: exit-code) since Tue, 11 Sep 2012 23:46:46 +0530; 30s ago Process: 5258 ExecStart=/usr/lib/systemd/scripts/vgaoff (code=exited, status=203/EXEC) CGroup: name=systemd:/system/vgaoff.service –  Sharique Sep 11 '12 at 18:17
1  
@Sharique - make sure your script is executable: chmod +x /usr/lib/systemd/scripts/vgaoff and the shebang line is not missing. –  don_crissti Sep 11 '12 at 19:16
1  
@Bazon - according to this logic, thousands of answers on this site are "potential traps" for inexperienced users. People who don't know / fully understand what echo SOMETHING > /some/file does (or any other command as a matter of fact) should get familiar with the basics of CLI before attempting to run stuff on their systems. That aside, FYI, read how to switch dGPU off on several laptop models, see if the commands used there could be replaced with something like you suggest. Also, to restore the original file you usually reinstall the package that owns it. –  don_crissti May 14 '13 at 23:56
1  
@macmadness86 - yes, in this case /etc/systemd/system is the right place; thanks for the heads-up ! This is an old post, at the time of posting I had my vgaoff script and systemd unit in a package built with makepkg and I copied the paths from my system... It's now corrected. –  don_crissti Aug 23 at 22:32

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