System has not been booted with systemd as init system (PID 1)

Hi all,

Everything was swell until yesterday when Home Assistant stopped working for me. I’m running it on a raspberry pi 4 on top of Rasbian.

When I type

systemctl start [email protected]

I get the following error:
System has not been booted with systemd as init system (PID 1). Can’t operate.
Failed to connect to bus: Host is down

Does anyone know what is going on and how I fix it? Thanks!