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Almost Perfect Disk Crash Recovery

posted Oct 31, 2011, 9:11 PM by Vick Khera
The other day my daughter told me there is some beeping near the main family iMac.  I sounded bad to me, so I set it to shut down.  It never completed.  When I powered it off a while later, the beeping stopped.  Clearly something bad was happening with it.

I tried to reboot it, but all I got was the flashing question mark of a missing boot volume.  Sadness.

As it turns out, the brand new disk (almost exactly one month old) failed.  I had it upgraded recently to give me more room to hold all my pictures and music.  The store replaced the failed drive and I just finished the restore from the time machine backup using the Lion Recovery Disk on a USB stick.  It was all incredibly slick.

Once it rebooted about 7 hours later (the disk was network mounted, not directly attached), I decided to check everything out.  There were three programs that failed to run: Firefox, Thunderbird, and Chrome.

Firefox and Thunderbird both complained they could not read my profile.  Easy test was to move the profile directory (and indeed, the entire Firefox and Thunderbird directories under Application Support) out of the way and restart.  Still, same error.  Then I found some web page that said to try running the binary directly on the command line.  This showed me the error message Error: Access was denied while trying to open files in your profile directory.  A quick google search later, and the most improbable solution was offered:  Run sudo chown -R vivek ~ to fix the ownership of all files in my home directory.  At first I couldn't see how this could work.  I had already compared the file permissions of my Firefox directory (and all directories above it) to those on a working machine, and all was the same.  Nevertheless, I decided to go ahead and try it.  Amazingly, it fixed all three programs.  I still have no idea why this fixed it, but I have better things to worry about.

All in all, the Mac OS Time Machine is absolutely amazing.  The simplicity of recovering from a complete disk failure is astonishing.  The recovery USB stick image booted, found my network backup, and restored it to near perfect working condition with zero data loss.  All my pictures are there and all my music is there.  Needless to say I'm anxiously waiting for the current backup to complete.  I think I may also get a second backup drive to keep my most precious files off-site and back it up once a week or so.