This is our experience in standing up another Avalon system on the same host to do red black blue-green deployment.
Clone Fedora
In Tomcat, copy webapps/fedora to webapps/fedora3.
...
Cap deploy from your local machine to server. For really large repo, you may want to migrate and reindex separately in a screen/tmux session.
Make sure your background jobs are running and pointing to new Avalon location.
Reindex Solr
Manually kick off rake avalon:reindex. This can take a very long time if you have a large collection, better run it in a tmux session.