Comment 1 for bug 1844773

We used to have config-changed trigger whenever a unit agent was restarted, but the feedback was that caused outages because of charms that force restarted their application whenever the hook was called (regardless of whether there was actual change relative to the last config of the application.)

I'm curious what actual event you're looking for/what you want to do in "machine was restarted".
Wouldn't that be a systemd process that starts your instance?

leader-settings-changed certainly doesn't seem reliable for this. It might only be triggering for the same reason that config-changed used to trigger (during initialization we just assume NewValue != UnknownExistingValue).

It would be good to concretely understand what you're looking to run/alert/do something. (Generally we don't recommend starting an application process directly as a result of a hook, vs the hook configuring a systemd service. Otherwise there isn't any way that you would guarantee if the service dies it would get restarted, as there may be no Juju Model lifecycle event that would trigger another hook.)