Failed to restart elasticsearch.service: Unit not found

As an AI language model, I don't have access to your specific system environment to provide a tailored solution. However, I can suggest some general troubleshooting steps:

1. Check if Elasticsearch is installed properly by running the command `sudo systemctl status elasticsearch.service`. If Elasticsearch is not installed, you can install it using the appropriate package manager for your operating system.

2. If Elasticsearch is installed, try restarting the service using the command `sudo systemctl restart elasticsearch.service`.

3. If the above command fails with the error "Unit not found", it could mean that the Elasticsearch service is not properly registered with the system. In this case, try re-registering the service using the command `sudo systemctl daemon-reload`.

4. If the above steps do not work, check the Elasticsearch logs for any error messages using the command `sudo journalctl -u elasticsearch.service`.

5. If you are still unable to restart the Elasticsearch service, seek help from the Elasticsearch community forums or consult a professional Elasticsearch administrator.