Whats the best way to get this done. The new master is an existing master of another multi server system. Is there a script for this? Or must it be done in the database and then config on the slave? (Like adding a new server to a multi?) Thanks.
Examine ISPConfig Migration Toolkit, maybe ISPCopy does what you want. https://www.ispconfig.org/add-ons/ispconfig-migration-tool/
i don't think ispcopy will work, that will make an identical copy of the source server, the new copy will still expect to be connected to the old master the migration toolkit is probably the easiest option, although that means either transferring the existing services on the old slave to other existing servers on the target multi-server system, or creating a new server on the target multi-server system and migrating everything from the old slave to the new slave.