Problems on Mac OS X with owners and groups? For solution, read on...

Martin Koistinen mkoistinen at
Tue Aug 30 14:34:02 GMT 2005


This message is placed here for the aid of others in the future. I have 
search the archives for this solution, but sadly, only found a couple of 
(rather old) messages from people exhibiting having the same problems, but 
without any replies for this solution.

Please forgive me as I seem to ramble on here, I do so with the intent of 
making this solution more findable by others having this issue but don't 
exactly know what they are searching for.

The problem is characterized by copies made by rsync have reset owner and 
group information -- in my case to root : unknown -- regardless of the 
switch settings for rsync. So, for example:

# rsync -aog source dest

will copy all files from source to dest, but will not preserve the owner and 
group settings of the source files, even though the (redundant) flags for -a 
, -o and -g are all set.

To make matters worse, because of the problem, the whole --link-dest 
functionality doesn't save space in a backup/snapshot scheme for unchange 
files, since rsync will find that the dest files in the previous backup will 
have different ownership than the source files (unless the source files also 
happen to have root:unknown ownership, that is)

This problem is most likely to occur with those of us who have added extra 
disks to the system (probably) via firewire or USB.

The issues is not rsync, but rather a setting in the OS. OS X has newly 
formatted disks marked with a flag to "ignore ownership details on this 
volume" by default. To fix this, select the volume you wish to check/change 
in the finder. File -> Get Info (Apple-I), in the multi-panel, info-window 
for your disk, open the section "Ownership & Permissions:", and 
verify/uncheck the checkbox for "Ignore ownership on this volume".

Voila, the "rsync" issue is now gone.

I suspect that this ownership flag is set by default to emulate disk 
insertion behavoir prior to OS X on the Mac (where it was ignorant of 
ownership and/or permissions).

It would be great if rsync could verify that ownership settings actually 
took when they are set and report in the verbose output and/or logs if there 
is a discrepancy. This would help to aid those of us in setting up 
rsync-based backups and will forewarn us of related problems during full 
recovery of a backup.

I hope this helps someone and/or aids the future development of rsync.

-- MKoistinen
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