I've already read this SE question, but it's somewhat old now. How can I reencrypt a LUKS partition using a different master key? I have a cloned VM image that needs to go into production, but it's obviously using the original VM's master key. When I install cryptsetup-reencrypt, I see a scary message:
[root@server ~]# cryptsetup-reencrypt /dev/xvdd1
WARNING: this is experimental code, it can completely break your data.