How to restart a service if its dependent service is restarted

Question

A service (say bar.service) is dependent on another service (say foo.service), like below

bar\'s service file:

[Unit]
After=foo.service
Requires=foo.serv         


        

Answer 1

A another solution might be to use ExecStartPost option to restart the bar.service (if it´s executed) when foo.service has (re)started:

# foo.service
[Service]
ExecStartPost=/bin/systemctl try-restart bar.service
Restart=on-failure
RestartSec=30s

The additional Restart and RestartSec options ensure that foo.service will automatically restarted on crash and thus also bar.service.

A second extension my be to add same to bar.service and ensure that bar.service start after foo.service:

# bar.service
[Unit]
After=foo.service

[Service]
Restart=on-failure
RestartSec=30s

This should start both services automatically in case of a crash and bar.service will be restarted when foo.service restarts (due to an error or manually triggered).