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Old 06-10-2005, 02:13 AM
steve steve is offline
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Join Date: Jun 2005
Location: Billings, MT
Posts: 4
Question Concerned about hard links

I'm a new owner of SuperDuper, and I've been doing some testing under Mac OS X 10.3.9.

One discovery has me a bit puzzled and concerned. After doing a simple clone operation to create a bootable volume, I see that hard links are apparently not preserved. This can be observed in Terminal by using the "ls -li" command. Source files (not directories) with a link count higher than 1 inevitably show up on the target with a link count of 1.

Examining inode numbers adds more evidence that hard links are lost. Instead of multiple directory entries sharing a single inode number, each directory entry ends up with a unique inode number. That means that the original file, which had multiple directory entries pointing to it, has been duplicated so that each directory entry points to its own copy.

This seems like a waste of space, but more importantly, could lead to software malfunctions if hard links are assumed to exist when files are updated. Do we know that all those hard linked files are never manipulated by Mac OS X, so there's no need to worry? Couldn't third party software use hard links and get tripped up by this too?

Hard links are especially abundant in /usr/share/...; there are hundreds and hundreds of them. (A simple test directory is /usr/share/zoneinfo/US.)

For comparison I tried cloning using the asr command in Terminal, and also Carbon Copy Cloner (which uses the ditto command). They both play it safe and preserve hard links.

I'm new to SuperDuper, and I'm no expert on unix either, but this seems like an issue worth exploring. Anyone more savvy about these things have any thoughts?

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