I’m running Klipper & Octoprint on my Orange Pi Zero to control my 3d printer. Sometimes Klipper breaks, and power needs to be cycled to fix things.
One big problem is that Klipper needs to be running all the time to control the hotend fan, since leaving it off for too long when the hotend is hot can cause clogs. At the moment, klipper only starts up 23s after the power is applied, as shown by systemd-analyze plot.
klipper.service
All that klipper needs is a TTY and /tmp, so it doesn’t make sense to wait for the network.
In my case, the TTY is /dev/ttyS1. So I needed to replace the After= in my service file with After=dev-ttyS0.device.
However, systemd adds the sysinit.target target as a dependency to all services by default. We know better here, since klipper has such limited dependencies. We can override this using DefaultDependencies=no.
But when we’re telling it we’re smarter than it, we have to also tell it we need a filesystem. An additional After=local-fs.target line must be added.
keyboard-setup.service
Not sure what this is, but this is a headless machine and doesn’t require it.
Results
Before, we started klipper at 23s from power-on.
After these changes, klipper starts at 9s from power-on.
Unfortunately, we can’t do much about that. Systemd only starts executing units at 7.2s, and Linux only finishes loading in at 5.5s. The initramfs is compressed, but still takes up 9.4MiB–huge for a slow SD card.