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I'm about to upgrade from 10.5.8 to 10.6 (Snow Leopard). I intend on backing up applications, documents, downloads, and other files to a Mac formatted external USB harddrive.

Recently, I attempted to copy a VMWare Fusion created virtual machine to the drive, and then from that drive, move it to an Ubuntu host. The virtual machine file was actually a package, and within that package, files were given restrictive permissions. In other words, many files were only readable by the staff group and not the everyone group. So, the result was that the Ubuntu machine could not open the virtual machine until I'd taken the files back to the Mac, then changed the permissions so that "everyone" could read the files. I've seen similar behavior on Windows machines that are part of a domain with encrypted/protected drives. These experiences make me wonder, is it ok to back-up to this Mac formated drive or should I use a another harddrive that is FAT32 formatted so that the permissions aren't restricted?

I plan on doing a clean installation, complete formatting, etc. not an upgrade. I come from Microsoft's world and haven't quite gotten used to the idea that an operating system plays nice on upgrades.

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For the record, Snow Leopard's "upgrade" process actually does a clean install and then migrates stuff over. It plays very nice. –  jtbandes Aug 30 '09 at 6:35

2 Answers 2

You should use a Mac-format drive, so that it can properly store all the ownerships, permissions, and important parts of files that might otherwise be lost.

(If you only had a FAT32 drive, then you could have created a sparse image on there, mount that on your Mac, and copy the data onto it.)

Personally, I'd use SuperDuper! to generate a bootable disk of my existing system, any time before I upgrade it. Or, at least make sure your TimeMachine backups are up to date, and not excluding any important data.

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I upgraded my Mac OS X the same way you described and it worked without any problems. I don't quite understand how Snow Leopard knows, that the user named Tomas that owned the files on the external drive on Leopard is the same Tomas on Snow Leopard, but all permissions are the same as they were before the upgrade.

And those files that were not mine, are still not mine, but belong to some user called _unknown. But I can just authenticate as an admin and set read & write permissions for those files for my user, so there are no problems accessing them.

Maybe it just checks for the User ID and if it matches (in both cases I was the first created user and probably had the same User ID). If someone knows exactly how it works, I would like to know it too.

Oh and I also created a SuperDuper! backup of my disk and in that case all of the files on it seem to belong to me (even those from other users in /Users/*).

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