Computer will not start after update. Won't boot. Security Update. Grey.

Question

This is a fix that worked for me. 2 times in the past Automatic Software update has corrupted my hard drive.
When installing using SOFTWARE UPDATE the installer for the security update fails, says it has been moved to trash and to try again. Well if you restart, you get a system hang and much sadness.
I tried the usual stuff, booting from CD(osx) and selecting the disk utility from the top menu. But that didn't fix it. Then I ran DiskWarrior, which usually fixes anything, but it didn't this time.
Here is what did work. I checked my other mac to see what the last security update was, and it had the 2009-001 update (worked on that mac). So I knew now that the one that screwed up was that update.
I downloaded that update to my laptop.
I started my iMac (the one that crashed after update) in "target disk mode" - this treats the whole computer as an external firewire disk drive (it's totally safe as long as you don't erase anything) - you start into target mode by holding down "T" key while turning on, leave it pressed until you see a symbol on the screen that looks like a "Y".
I hooked up a firewire cable from the iMac to my laptop and waited until the iMacs Hard drive appeared on the laptop desktop.
Now you can browse the corrupt drive just like a regular external drive.
If you have an external drive with room, this is a good time to back up the entire corrupt drive to a folder on the other external just in case...
But what I have found is that when the installer for the security update failed, it corrupted the file that mac osx needs to read during boot, so it is an isolated failure, but it is always better to be safe.
at this point you are ready to attempt the repair..
On my laptop I ran the installer for the security update I had manually downloaded from apples site. When asked for destination for the install I select the HD for the iMac (or whatever unit has the no boot situation that got corrupted). (note that if you have not renamed your main hard drives, you will have a choice of 2 with the same name). Usually the drive on the computer you are using will be first in line. Rename the drive on the computer you are using before running the install if you want to be sure there are no mistakes..)
Select the disk you want to (re)install to, and let it go. It is a long update, so be patient and let it finish. It should say preparing install, installing, finishing, and optimizing system performance...
When it says that the installation completed successfully you can eject the corrupt hard drive by dragging to the trash to dismount it. Then unplug the firewire cable.
Shut down the repaired (hopefully) machine by holding the power button until it turns of.
Count to ten.
Prepare a celebratory or misery soothing beverage (but keep it in the other room).
Some people like to start in safe mode by holding down shift key while turning on, but I couldn't get it to work on mine...
Turn the computer back on and wait. The boot process will take longer than usual the first time.
If and when you get to login or desktop, go in and run apple disk utility and repair the disk, and repair the permissions.
If it worked, breathe a sigh, do a happy dance. And from now on when mac os says there are updates available, write them down, then go to apples site, download them manually, and install them manually, one at a time from now on, to avoid hassles.
Hope this helps!
Enjoy!

Answer 1

Thanks for the post/tips newfocus, hope it helps somebody!