How best to restore Macbook Air (OSX Lion) from backup?
July 24, 2012 8:42 AM   Subscribe

What is the best way for me to restore my Macbook Air to full functionality, given that the it won't boot due to a corrupted file?

So, I started up my Macbook Air yesterday and it wouldn't boot. Command-V at boot revealed that the filesystem is currupt; in particular, it hung up on a specific file (/private/var/db/dslocal/nodes/Default/sqlindex-shm). The problem cannot be fixed by Disk Utility. The harddrive is encrypted with Filevault2.

Luckily, I have a backup (using CCC), but it is a day old (and that day had some important work and apps installed that I'd prefer not to reinstall). I installed Lion on a USB stick, booted up, and used CCC to clone the whole hard disk to an external USB drive. I could mount, but not write to, the corrupted drive. As expected, it had problems copying the particular corrupted file. So, I copied my day-old backup of the offending file to the external USB drive, and now I can boot my system off that. Yay!

But it wasn't without a hitch. Several apps seem to think that they hadn't been run before (like dropbox and textwrangler). I assume that this might be caused by the Volume name change? Everything SEEMS fairly normal, though. So, at this point, I wonder how to proceed. Here are my options, as I see them:

1. Reformat the corrupt hard disk, and copy all files off the USB external HD to the newly formatted internal drive, and hope that there are no other issues with corrupt files that I didn't know about. If I do this, how do I format the internal drive so that the OS will know to boot off it? Should I encrypt it, or leave it unencrypted and then enable filevault2 again after booting off it successfully? How can I check that everything is OK once I successfully boot of the reconstituted internal drive?

2. Install OSX Lion clean. I'd rather not do this, due to the problem of reinstalling apps, redoing cron jobs, etc. But at least this way I minimize the chances that other OS files are corrupt. If I choose this option, how can I minimize the pain of reinstalling apps? What about apps like MacTex and ParagonNTFS, that have files in places other than the Applications folder? Can I just copy those over, too?

So, which of these routes should I take? Or is there a third route that would be even better? Since I have full backups, it seems like I'm pretty flexible.

*(I should mention that for speed of backup, I excluded large, relatively expendable files, like VM hard disk files that I can remake, from my regular backups. So restoring from the day-old backup would be some trouble, on top of just restoring the old work.)
posted by Philosopher Dirtbike to Computers & Internet (5 answers total) 1 user marked this as a favorite
Let me congratulate you on having backups.

Try DiskWarrior. It's pretty amazing at fixing corrupted volumes.

MacBook Air computers come the ability to boot to a recovery volume either locally or over a wireless network. Hold down "command-R" as you restart. has details.
posted by blob at 8:57 AM on July 24, 2012

MacBook Air computers come the ability to boot to a recovery volume either locally or over a wireless network. Hold down "command-R" as you restart.

I did that; that's how I was able to install Lion to a USB stick and access the drive contents in read-only mode. I was thinking of trying DiskWarrior, but given that I have access to the drive and a backup of the file that seems to be keeping it from booting, it seems like shelling out $100 for DiskWarrior might be unnecessary - hence the two options above. I would probably buy it if it came with a demo version that told me what it could restore, or if it came with a money-back guarantee, but I don't know if it will improve the situation at all, given that I SEEM to be so close to fixing the issue.
posted by Philosopher Dirtbike at 9:03 AM on July 24, 2012

I'd go with a different option:

3. Restore the day-old backup to your hard drive. Then copy over from the corrupt drive any individual files that you modified in that one day. This minimizes the chance that other things are corrupted, but requires no effort to be spent reinstalling everything.

If you need help identifying modified files, let me know and I'll elaborate further.
posted by vasi at 3:43 PM on July 24, 2012

Looks like I'm back to normal. I formatted the bad partition and restored from my backup. In the process, I wiped my Lion Recovery partition. I used these instructions to rebuild it, and then I could again enable Filevault2.
posted by Philosopher Dirtbike at 11:00 AM on July 26, 2012

Glad it worked out. Just a note, if you can't identify a reason that the data became corrupt in the first place, there's a chance that your hard drive is failing. It might be a good idea to do a "bad blocks scan" at some point just to make sure.

Unfortunately there are no free user-friendly ways to do this scan. If you're feeling your techie side, there exists a program you can download and run from the Terminal, here's a guide.
posted by vasi at 10:20 PM on July 26, 2012

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