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.
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.