Cannot disable systemd serial-getty service

Question

On Raspberry Pi with Arch Linux there is a service active called serial-getty@AMA0.

The unit file is: /usr/lib/systemd/system/serial-getty@.service

As root I can invoke

systemctl stop serial-getty@ttyAMA0
systemctl disable serial-getty@ttyAMA0

But after reboot the service is enabled and running again.

Why is the service enabled after disabling it? How can I disable it permanent?

UPDATE

systemd uses generators at /usr/lib/systemd/system-generators/ is a binary called systemd-getty-generator. This binary runs at system start and adds the symlink serial-getty@ttyAMA0.service to /run/systemd/generator/getty.target.wants.

I eventually found a dirty solution. I commented out all actions in /usr/lib/systemd/system/serial-getty@.service. The service did appear to start anyway, but without blocking ttyAMA0.

Answer 1

The correct way to stop a service ever being enabled again is to use:

systemctl mask serial-getty@ttyAMA0.service

(using ttyAMA0 as the example in this case). This will add a link to null to the entry for that service.

Answer 2

Try this code:

system("systemctl stop serial-getty@ttyAMA0.service");
system("systemctl disable serial-getty@ttyAMA0.service");

I use it, and it works well.