Can't get inheriting TM to work (Big Sur) I have a similar problem as described in
Inheriting Time Machine and merging old history
and after cross-checking the tmutil man page and other posts on the issue I am pretty sure that this solution should work for me as well.
My mount point on the old computer was 'Macintosh HD', the mount point on the new one is also 'Macintosh HD' but time machine created the new name 'Macintosh HD Data' for the snapshot volumes. Thus the old snapshots all have snapshot volumes 'Macintosh HD' and the new ones have snapshot volumes 'Macintosh HD Data' and an additional directory 'Macintosh HD' which has
the time stamp of the latest snapshop before changing to the new computer and is just carried forward from snapshot to snapshot.
I tried
sudo tmutil associatedisk -a &quot;/Volumes/Macintosh HD&quot; &quot;/Volumes/Time Machine Backup/Backups.backupdb/Christian Fischer’s iMac/Latest/Macintosh HD&quot;

and variations like
sudo tmutil associatedisk -a &quot;/Volumes/Macintosh\ HD&quot; &quot;/Volumes/Time\ Machine\ Backup/Backups.backupdb/Christian\ Fischer’s\ iMac/Latest/Macintosh\ HD&quot;

including pasting the paths from Finder - without success.
I keep getting the error message
Usage: tmutil associatedisk [-a] mount_point volume_backup_directory
A local volume mount point and a snapshot volume path are required.

Am I doing sth stupid ? Or did the syntax change (I am using Big Sur 11.01 and read elsewhere that there were some syntax changes in tmutil delete...) ?
I had the same issue.
Seems to me that the -a option of tmutils is broken in Big Sur (11.2.1).
However, instead of letting tmutils perform the association on all volume stores:
sudo tmutil associatedisk -a &quot;/Volumes/Macintosh HD&quot; &quot;/Volumes/Time Machine Backup/Backups.backupdb/Christian Fischer’s iMac/Latest/Macintosh HD&quot;

you can do the association for each volume store yourself:
for f in &quot;/Volumes/Time Machine Backup/Backups.backupdb/Christian Fischer’s iMac/&quot;*; do if [[ -d &quot;$f&quot; ]]; then sudo tmutil associatedisk / &quot;$f/Macintosh HD&quot;; fi; done

This worked for me like a charm ;-)