Thanks Agustin & Leandro for highlighting this issue, and for finding a workaround.
After some investigation, I think I have narrowed the problem down to changes in behaviour of the automatic setup of entries in the /dev/ filesystem with the newer trixie tooling. It appears that although it was safe to assume that cryptmount devices would always be named "/dev/mapper/<target_name>", there is a tendency for these to be automatically renamed into symlinks of the form "/dev/disk/by-id/dm-name-<target_name>". This even appears to occur when mke2fs is run on a a device in /dev/mapper/, which subsequently disappears. I'm currently exploring how best to handle this portably within cryptmount, perhaps via dm_device_get_name(), but it's obviously awkward that we can no longer just use dm_dir() as the path prefix for devices created by cryptmount. RW Penney
