Unit tomcat.service could not be found.

This error typically occurs when the systemd service file for Tomcat is missing or cannot be located.

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

1. Verify that Tomcat is installed on your system and that the service file exists in the correct location. The default service file for Tomcat is usually located at `/etc/systemd/system/tomcat.service`.

2. If the service file is missing, you can create it manually by copying the example file from the Tomcat installation directory. For example, if you installed Tomcat in `/opt/tomcat`, you can create the service file by running the following command:

   sudo cp /opt/tomcat/bin/catalina.service /etc/systemd/system/tomcat.service

3. Once the service file is in place, reload the systemd daemon to recognize the new service file:

   sudo systemctl daemon-reload

4. Finally, start the Tomcat service:

   sudo systemctl start tomcat

You should now be able to access Tomcat through your web browser at `http://localhost:8080`.