You can add and remove hosts for your applications. You cannot rename an existing host, but you can create applications named after a host or cluster.
To add a host for monitoring, install the agent and start up your application. The host running the application will be identified to New Relic and will automatically appear on the site after a few minutes.
There isn't a way to change the host name. However, you can create applications named after a host or cluster. For example, if hosts ey01-s00057 and ey01-s00058 are both part of a production tier, you can create an application called "App - Production" and have those two hosts report to it.
To remove a host, uninstall the agent, or disable it by editing or removing the newrelic.yml configuration file. Make sure that all application server instances (Passenger, Jetty, etc.) have been fully restarted after disabling the agent.
Occasionally, rogue application server processes will linger on and continue reporting data. You will know this is the case if your app's "traffic light" status is green, even though you shut the agent down and verified that no data is reporting. Check your web server for stray processes, or get support at support.newrelic.com.
Once all reporting applications are shut down on the old host, it may take up to 10 minutes for the old host to disappear from the New Relic list and the new one to appear.
Additional documentation resources include:
If you need additional help, get support at support.newrelic.com.