exit init-process when all services have died about docker-systemctl-replacement HOT 4 CLOSED

I have cut out the remaining features to "exit init-process when the required services have died" #27 ... while I am closing this ticket for the current milestone. In most situation it will do what is expected.

Note that I was rethinking it also as may be one could use /usr/bin/systemctl as the main process before running an actual service. In reality I found that simulations of an operating system in a container had the "cron" and possibly "sshd" running. So the list of processes is not empty.

from docker-systemctl-replacement.

Note however that the kubernetes restart-policy includes livenessProbe / readinessProbe actions that do not rely on the existance of a PID-1

https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy

from docker-systemctl-replacement.

I can add that

1. the timeout is useful to debug (otherwise, a restart policy set to always will loop and one cannot enter in the container to do some debug).
2. when there is an error, init should return not 0.

from docker-systemctl-replacement.

Instead of checking for dead services I have impemented atleast the most basic condition for an exit - if the systemctl.py init process finds itself to be alone in a container then it will exit. In the case that all the "systemctl halt" services have correctly stopped, thereby killing all its children, then the systemctl.py will stop as well.

That's also okay for a debugging POV as there is nothing left to attach to.

The only missing point is the exit status of PID 1. What shall it return? A forking service will not transmit an exit code. Neither oneshot - basically it does only make sense when there is a type=simple service and one would ask systemctl.py to mimic the behaviour as if someone has been extracting the ExecStart statement to make a docker-entrypoint.sh with a final exec-$cmd. Or is there more to it?

from docker-systemctl-replacement.