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Use UFS for shared external drives
Authored by: ducasi on Aug 30, '07 07:46:11AM

Fred should untick the "ignore permissions on this volume" box in the "Get Info..." for this external disk. :)



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Use UFS for shared external drives
Authored by: dbs on Aug 30, '07 09:03:13AM

Actually, the user IDs are just stored by number on the drive, so this may not help.

If the first account created on Computer A was "fred" and the first account created on Computer B was "sally" then they will both have UID 500. So even if you respect the permissions, Sally will still see all of Fred's files as hers and have full rights to them.



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Use UFS for shared external drives
Authored by: ducasi on Aug 30, '07 09:41:02AM

Indeed, if the drive is used on multiple machines, then you can get UID clashes. Formatting the disk as UFS will not help here though.

The answer to this is for Fred & Sally to both have accounts, created in the same order on both machines so that their UIDs match up across the two computers. Or better still, have a "server" computer that they both have accounts on, plug the shared disk into it and then they can both access their own files on their own computers at the same time!



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Use UFS for shared external drives
Authored by: Andrew Fletcher on Sep 01, '07 01:35:01AM

I had tried unticking the "ignore ownership" button before I wrote the hint and that had had no effect on the ownership as far as I could see. However, with all the comments on this thread saying otherwise I tried out HFS+ on a small flash drive to see if I could work out what had gone wrong when I'd used the HFS+ hard drive.

All of this is on one iMac running 10.4.10 with all software updates applied. There are two users involved: "admin" who is an administrative user, and "fred" (not his real name) who is a standard user.

"admin" HFS+ formats the drive as "hfsplus" and does a "Get Info" on it and unticks the "ignore ownership" button and closes "Get Info". He then puts on a folder called "Users" and creates two folders in "Users" called "admin" and "fred". Using "sudo chown" the ownership of "fred" is set to "fred".
This all works as the comment makers expect. "fred" can't write into Users/admin on hfsplus and can't delete Users/admin. "fred" can write into Users/fred OK.

However, the security of the files are at risk because "fred" can tick the "ignore ownership" of hfsplus in "GetInfo" and then he can delete "/Users/admin". Curiously, if "fred" then tries to untick the "ignore ownership" button the usual "Authenticate" dialogue appears requesting an administrative a name and password.

I can only assume that while I was setting up the HFS+ hard drive I had ticked the ignore ownership in "fred" and had looked at an already open "Get Info" in "admin" and had seen it unticked. Or something like that.

However, given the insecurity I've seen, I feel inclined to stay with UFS format despite the warnings. For the record, iPhoto, iTunes, Photoshop Elements 2 and various other applications seem to work OK using files on the UFS drive. I have tripped over the case sensitivity problem, but in that case it was easily worked around. I rarely use the Classic OS 9 environment and I can be careful to only use files on my start-up disk if I do.



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