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Why won't my cloned drive recognize the Time Machine backup?

After encountering temporary battery problems with a Macbook Air, I used Carbon Copy Cloner ( http://www.bombich.com/ ) to clone the drive. Then I transferred the cloned drive into a Macbook with the intention of using that instead of the Macbook Air. Everything worked fine with the Macbook -- except that it wouldn't recognize the Time Machine backup associated with the Macbook Air.

Anyone have any idea why the computer with the cloned drive wouldn't recognize the Time Machine backup? I'm wondering if there's something about Time Machine that records data about the actual physical machine that originally created a backup so that it won't work with a cloned drive.

Answered! View the answer I have this problem too

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my understanding is that the Time Machine backup is attached to the MAC address (i.e. ethernet address) of the computer. so even if you cloned the laptop's boot disk, by moving it to another machine your TM backup no longer associates itself with that machine, even though the hard drive contents are same as original.

Unfortunately I found this out recently when moved my disk contents from an old iMac to a new one, and my old TM backups didn't just continue where they left off. I ended up just restarting my TM backups from scratch since I already had a separate bootable clone backup of my entire disk (using SuperDuper!, another great cloning tool, btw)

here's some info I found on the subject over at Mac OS X Hints - I've not tried this myself (too late! see above) but it sounds reasonable.

if you still have your TM backup, perhaps give it a try and report back here if it works. good luck

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Thanks a ton for the info and the link! Unfortunately, I no longer have the backup, so I can test out the solution, but I know where to look the next time I have a similar situation!

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As sort of an addendum to this question, I've noticed that drives that have been cloned generally show the blinking question mark for an instant while booting up, just before they go to the Apple icon. I've always wondered why this is, and I'm wondering if the answer to this is the same answer as to why a Time Machine backup wouldn't work?

In the PC world of disk cloning, there is the concept of the SID (security identifier) that is randomly generated when a manual install is done for an OS, and when you dump a clone of an OS, you have the occurrence of multiple machines with the same SID, which can cause problems. You therefore need to use some type of "SID scrambler" in order to rectify the situation. I'm clueless how this goes on the Mac side, however, or if it's related to Mister790's question.

Maybe the Time Machine backup has the same "SID" as the computer being used?

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"drives that have been cloned generally show the blinking question mark for an instant while booting up..." Usually all that this requires is a trip to the Startup Disk control panel to choose the new disk.

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I actually used a similar MacOSX Hints tip to re-associate a TM backup to an upgraded HD. The backup files have an imbedded UUID (unique identifier) so they know exactly what drive they're backing up. It appears TM recognizes the MAC address of the computer also.

After fiddling around with that, though I eventually got it working, I decided that in future it's just easier to let the backups start over again, and eventually delete the old backup.

This applies to USB-connected TM drives, not Time Capsules, which use a sparseimage to store the backup, and is probably more complicated to tweak, if it's possible at all. In that case I would definitely let the backups start fresh.

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mister790 will be eternally grateful.
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