What do you do when Mac OS X will not boot?

Well, I learned the hard way twice… I live a largely paperless life, my laptop (a MacBook Pro 17″) has my business world on it, I am a backup freak with Time Machine running along with Retrospect remote (or whatever they call the network service these days), and periodic backups of the backups taken off site for storage. When I am at the home office I have access to all kinds of tools, along with the backups, to get me out of trouble.

However, what do you do when you just landed thousands of miles away from your office and when you press the power button you never get to the login screen? I have run into this issue twice and here are the paths that got me up and running. I, fortunately, did not have a hardware issue either time and nor did I need access to my backups. (There is only so much I am going to travel with) So with some luck the below might help you as well. Be warned however! The actions below might take you into deeper trouble and kill some of the data on your system (you do have a complete backup at home? Right?) while on the other hand they might just save the trip you made from being a complete disaster.

The two scenarios that the below saved me from were quite different. The first was a situation where the Mac seemed to be booting normally but stalled on a clear blue screen with a spinning beach ball cursor. The second was a case where during the boot process the system was actually shutting itself down with a CPU halt. If one of these sounds familiar, or if you are brave enough to try the below out on a different situation, here we go…

Start with the basics and reset the PRAM and NVRAM:

Resetting PRAM and NVRAM

  1. Shut down the computer.
  2. Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
  3. Turn on the computer.
  4. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
  5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
  6. Release the keys.

Most likely resetting the PRAM and NVRAM did not do anything but it is always worth a try. If it did not work try booting in single-user mode. To do this boot the Mac with the Command-S held down. If you see a bunch of stuff start scrolling down a black screen and eventually end at :/ root# prompt this is a very good sign. If you have no luck booting in single-user mode then scrolling down to the second path might still be worth a try.If you have trouble with the below because the disk is in a read only mode enter:

mount -uw /

and everything should be fine.If you are getting a CPU halt during the boot process try running:

fsck -fy

The very fact that the system cannot recover on its own will probably mean that fsck will fail. Under normal circumstances fsck might find some errors, fix them, and end with a message that the disk has been modified. If this is the case, run it again until you get a message stating that the disk appears to be okay — this might take up to four times. When you finally get the okay message do a:


…and all should be okay. If you are hosed in a way that fsck cannot recover from it will simply fail and not modify the disk. So, here we split into two paths:1) fsck is ending fine but I still cannot boot. The process proceeds when I reboot to end on a blue screen with the beach ball cursor spinning and just sits there forever. In this case boot in single-user mode again and navigate to the /Library/Caches folder and delet all of the *.csstore files.

cd /Library/Caches
rm *.csstore

If you a technical user and want to poke around before doing the above you can try to see the system.log file in /var/log and see what might be going on in /Library/logs/CrashReporter as well.

After the cache files are removed do a “reboot” and hopefully all should be well.

2) If fsck is saying the disk is in trouble there is really only one way that I would recommend to continue from here and that is with DiskWarrior. If you are not prepared you might be lucky and find a copy at a local computer store or Apple store that is fresh enough to be able to boot in your system — but if there is an Apple store in the area you might as well just bring in your system! This will certainly work – however relying on finding a copy, or better yet an Apple store, locally is not a great idea. The second best thing to do is keep a DVD with you — however, traveling with a DVD and keeping it scratch free along with betting on nothing is wrong with your DVD drive is too much risk for me.

Here is what I suggest doing obviously well in advance before anything bad happens:

Buy a copy of DiskWarrior.

Buy a DataTraveler 200. (32GB is far big enough for a rescue stick)

At your leisure format the DataTraveler using DiskUtility with one partition and a GUID Partition Table in the Options… button. Of course I am assuming you are running an Intel Mac and if you do not select the proper partition format you will not be able to boot from your USB drive. From here install a fresh copy of Mac OS 10.5 on it and let the updater do whatever it needs to bring the system up to date. (This will take a long time via a USB flash drive) When you have a working copy of Leopard installed you can then add DiskWarrior to the drive along with any other recovery tools you might want to have with you on the road.

So, you had the above prepared but how do you boot from it? Simply plug it in a USB port and boot with the option key held down. You will be presented with the boot manager a

llowing you to select the rescue stick you created ahead of time. From here you can run DiskWarrior which has been my savior for many a disk problem. While I was away it found a good number of errors it was able to correct and a few orphaned files that I had to put back where they belonged after it ran. Fortunately nothing was actually corrupted. (Hint, if you are using a DiskWarrior DVD then boot from it by holding down the ‘C’ key)

Not much is going to save you from a dead or massively corrupted hard drive on the road but the above might just get you working in most cases. Why a USB flash drive instead of a portable hard drive? As attractive the small hard drives are in today’s world — heck, with a large capacity one you would probably be able to create a small rescue partition (as defined above) as well as maintain either a Time Machine backup or better yet a SuperDuper! image on the same drive. The real answer comes down to how much are you going to take on your travels and how reliable do you want your tools to be. For me the idea of something that takes up almost no space and has no moving parts to break is a perfect concept.

One final warning! DiskWarrior as with any other disk recovery program can work as much magic as it can do harm. If you are stuck (and have the peace of mind of a backup at least somewhere in the world) then working directly on a bad disk may pose little risk…otherwise, good luck, you are really on your own.