I'm using a MacBook Pro 13'' mid-2012 running Mac OS X El Capitan (10.11.6).
My problem is similar to https://serverfault.com/a/402216/616473.
rsync to create backups from my internal drive to an external USB drive.
In order to save disk space, I would like the backups to be incremental. For that, I use rsync with the
--link-dest option. It should result with rsync not transferring the unchanged previously backed up files. Instead, rsync should create hard links to those files.
rsync -arv --link-dest=/Volumes/EXTERNAL-HDD/backup-1/ /folder-to-backup/ /Volumes/EXTERNAL-HDD/backup-2/
For example, the files that have been backed up during Backup 1, and that have not changed since then, should not be transferred during Backup 2. Instead, in the folder
backup-2/ should be hard links to those previously transferred files.
But rsync doesn't work properly in my case and it is not hard-linking the files (and is copying it twice). The reason for this problem is that rsync is not getting the real UID of the files : https://terminalapp.net/backups-rsync-and-link-dest-not-working/ because of the "ignore ownership" option that is enabled by default on Mac OS X.
So I would like to disable this "ignore ownership" option for the external drive. After some googling, I understand that there are two different ways : via the Finder (there should be a checkbox in the "Get Info" section of the drive) or via the Terminal (Change "ignore ownership on this volume" from the command line for Mac OS X volume).
I can't find the checkbox.
I tried to that :
sudo diskutil enableOwnership disk2s1
disk2s1 being my external drive.
But I got the following error :
Error enountered enabling user/group ownership: The underlying task reported failure on exit (-69860)
So, how the hell can I just turn off this
ignore ownership for my specific external drive ?
Thank you for your answers