To back up a disk image, you back up the .dmgfile itself, instead of the virtual disk the system shows you.
However, unless the disk image is a sparse bundle image. Time machine will have to backup the entire disk every time the disk changes.
I have the same issue since one of the mavericks updates, not necessarily the .0 version, not sure when exactly it started. I have this issue mostly with one folder: ~/Library/Preferences. I can fix the issue (see below), but 1-3 weeks later the issue is happening again with that folder. I think this folder might be hit often by the bug, cause the prefs-files in there are often changed, I dont know. Anway its a bug! If I should guess, the reason might be a bug in fsevents-daemon (fseventsd), which is responsible for tracking file system changes.
Sometimes I also have other folders than Preferences not backing up anymore, but this happens not that often.
To test which folders are "stuck" and do not backup properly you can:
- do a fresh backup and keep the backup volume connected
- in Terminal:
tmutil compare -n
The terminal command runs 30 mins with my backup of 150 GB size.
It helps identifying files which are not in the Latest backup. Be informed, some files might be shown, which are ok to be not backed up.
I also tried touch files, which did not help. What helped, was renaming the parent folder. To fix the issue for a particular folder, e. g. ~/Library/Preferences, I rename the folder twice like:
in Terminal:
sudo mv ~/Library/Preferences ~/Library/PreferenceS
sudo mv ~/Library/PreferenceS ~/Library/Preferences
Note, the last letter s/S at the end. I need sudo for the Preferences folder, cause OSX has set special access rights for that folder. So sudo might not be needed for other folders. After doing so, the files in that folder are backed up correctly again. Problem: the issue is not solved permanently. Unpredictably after 1-3 weeks the issue is back.
other links:
Best Answer
Can't you delete it from the Time Machine interface? Or is this a backup from a computer you no longer use? If the latter then there shouldn't be much/any risk in just force deleting it. If I remember right then you need to clear the immutable flag from the directory (or from all the files?)