How to reassociate Time Machine backup with the computer
sudo tmutil inheritbackup "/path/to/backup.sparsebundle"



  Machine directories and sparsebundles are owned by one computer at a time, and are tracked by unique identifiers rather than computer name, host name, or ethernet address. The inheritbackup verb reassigns the identity of the specified item, reconfiguring it so the current host recognizes it during backups. When inheriting a sparsebundle, the machine directory within will also be claimed.


This performs automatic inheritance of the computer and disk backups located within. This may not function correctly. If not, you may need to manually associate the disk within the backup with your current disk.

sudo tmutil associatedisk -a "/" "/Volumes/backupdisk/Backups.backupdb/computername/Latest/localdiskname"



  The -a option tells associatedisk to find all snapshot volumes in the same machine directory that match the identity of MyStuff, and then perform the association on all of them.