System has not been booted with systemd as init system (PID 1). Can't operate. Failed to connect to bus: Host is down. How to solve this problem?

The error message you mentioned typically indicates that the system is not using systemd as the init system. This can happen if your system is using a different init system or if there is a problem with the init system configuration.

To resolve this issue, you can try the following steps:

1. Check the init system: Confirm which init system your system is using. You can do this by running the following command:

   ps -p 1 -o comm=

This command will display the name of the init system in use.

2. Restart the init system: If your system is using systemd, you can try restarting it by running the following command:

   sudo systemctl daemon-reexec

3. Verify init system configuration: If your system is using systemd, ensure that the systemd configuration files are intact. You can check the status of systemd services by running:

   sudo systemctl status <service-name>

Replace `<service-name>` with the actual service name, such as `networkd` or `systemd-journald`. Look for any error messages or failures in the output.

4. Check for system updates: Ensure that your system is up to date with the latest software updates. Run the appropriate command for your distribution, such as `sudo apt update && sudo apt upgrade` for Ubuntu-based systems.

If none of these steps resolve the issue, it might be necessary to provide more specific details or consult with your system administrator for further assistance.