During the boot I’m seeing this one:
<<< NixOS Stage 2 >>> running activation script... setting up /etc... System has not been booted with systemd as init system (PID 1). Can't operate. Failed to connect to bus: Host is down starting systemd... Welcome to NixOS 21.03 (Okapi)!
rather than that, everything runs fine.
I’m not really sure what caused this, after I installed NixOS and later everything was fine, no errors whatsoever.
Any hint how to fix this?