Background
My friend asked me to look at her early 2011 Mac Mini with OS X 10.8.3. She said that:
- she installed software updates
- she couldn't remember which updates were installed
- when the Mac restarted, it hung at the Apple logo with the spinning gear wheel.
I used Disk Utility to check permissions and the disk. Both checks found a few errors, all of which were repaired. This did not help; after I rebooted, it hung at the same screen.
Several resets of the PRAM did not help.
Successes
A safe boot succeeded, the desktop appeared. I re-checked permissions and the disk; no errors.
Then a normal boot succeeded – this surprised me.
Question
Can anyone guess what was wrong and what was fixed?
Since it's not my Mac, and I don't know how it's really used, I can't guess.
I see Apple article HT1564, Mac OS X: What is Safe Boot, Safe Mode?, I'd like to understand more.
Best Answer
I assume that at least one of the updates required a restart.
As Disk Utility found problems with the file system, it's possible that:
No mention of force from you or your friend, so let's assume that:
In the 2013-05-06 edition of Apple's article:
Not only blue screens.
Alternative symptoms might include hangs of the type seen by you and your friend – the asynchronous progress indicator with the Apple logo.
Also, I do not find that a normal restart recreates that cache. To see whether the cache was recreated, at your friend's Mac in Terminal you might run the following command – be prepared for your friend to enter her administrative password at an on-screen prompt:
sudo update_dyld_shared_cache -verify
If the output indicates that a file does not exist, then there may be:
If the command completes with no visible output, there's no problem (the file exists and is verified).
Reference
update_dyld_shared_cache(1) Mac OS X Manual Page