I'm trying to back up an LVM volume using Duplicity (note: not just the file contents of the volume, but the actual volume itself, byte-for-byte).
The best way I've so far found is to
dd all the data on the LVM volume to a temporary file, include that file in the backup set, and delete it after the backup is made. This seems horribly inefficient, though: I'm needlessly thrashing the disk and duplicating all the data.
What would seem to be needed is a way to do essentially the opposite of
mount -o loop. In other words, I don't want to mount a file as a block device: instead, I want to 'mount' a block device as a regular (read-only) binary file — one that Duplicity will then read from and back up for me.
Is there any way to achieve this?