After making a full forensic copy of a harddrive using dd, I would like to keep up with changes between the original and backup harddisc, therefore I started using rsync.
Whenever, I run
sync -a -v -n --progress /media/drive1 /media/drive2
the command would start listing all files contained in drive1. However, only a couple of them has changed after I did DD.
Trying that on a single folder
sync -a -v -n --progress /media/drive1/folder /media/drive2
works fine and just displays the new files in that folder - those which are not contained in /media/drive2/folder.
However, executing the command on the level of both volumes
sync -a -v -n --progress /media/drive1 /media/drive2
does not account for the differentials, contrary to the documentation which is everywhere available, but takes all files which are already on both drives.
What is my mistake?
The way rsync treats its source and destination paths is easy to get wrong. When you use the command:
sync -a -v -n --progress /media/drive1 /media/drive2
...it tries to sync the drive1 folder into drive2; that is, it creates and populates /media/drive2/drive1. When you add "/folder" to the source path, it works as expected because then it's trying to sync with /media/drive2/folder, which is what you want.
Fortunately, the solution is easy: add "/" to the end of the source path, which tells it to sync the contents of drive1 into drive2, rather than the folder itself:
sync -a -v -n --progress /media/drive1/ /media/drive2
BTW, I'd recommend adding --dry-run to make sure it's doing what you want before running it "for real". You'll probably also have to delete /media/drive2/drive1.