It is possible to migrate an exising game server to LinuxGSM.
Install the LinuxGSM server of choice as normal.
Once installed there will be a vanilla install in serverfiles
Backup the serverfiles mv serverfiles serverfilesbak
create a new serverfiles directory mkdir serverfiles
Copy your existing server in to the empty serverfiles directory.
Ensure that the file structure matches that of serverfilesbak
i.e the executable, maps, etc. are in the same place.
Ensure the correct user permissions are used chown -r gameserver:gameserver serverfiles
Copy the game server config to the new config file location found in ./gameserver details
Run update to make sure you are up-to-date ./gameserver update
Test that the server works.
Once complete delete serverfilesbak