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I have an iMac w/ OSX, occasionally it hangs on boot (doesn't even have the apple logo or the animated spinner icon) and I would like to troubleshoot this to see what the problem is. I have to hold the on/off button so it shuts down, and then the next time it almost always boots fine.

Is there a way to have it display unix-style verbose text during bootup?

A friend of mine said I should look at /var/log/system.log and I did but couldn't see anything obvious this time. I'll try to be more thorough next time it happens, but it would be more helpful to see where it locks up.

edit: Please note -- 95% of the time my computer boots fine and runs fine. I just want to figure out what's going wrong the rest of the time.

update: happened again. Got the chord and the gray screen, no apple logo, no /var/log/system.log entry. It is an Intel Mac. I'll try the troubleshooting docs....

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For Intel Macs, see support.apple.com/kb/HT2674. The Command-V verbose boot option will really only take affect once the kernel gets going. It sounds like your system is stalling sometime before it gets to the kernel. If you have seen the Apple logo, it is found a boot partition. If you see the spinning gear, it is loading the kernel. It might be that your boot disk is having problems and causing a hang. Check its SMART status in Disk Utility. –  Chris Johnsen Nov 25 '09 at 2:57
    
consider changing that comment to an answer? –  Jason S Nov 25 '09 at 3:56

2 Answers 2

You can start it up in verbose mode by holding down the command (apple) and V keys.

Your description leaves more questions unanswered, as it sounds like it's not even made it to the OS yet. How long do you wait during this hang? Did you pick the boot choice in System Preferences » Startup Disk? What happens if you hold down the option key at boot (to provide you with boot options): does it not show anything or does it work properly?

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...but the thing is, I can't start it in verbose mode after I already have started it up; and I don't want to hit command-V every time I boot. –  Jason S Nov 25 '09 at 1:29
    
Never shut off the computer? They have sleep mode. I'd follow jweede's suggestion of the resetting the PRAM. –  Nerdling Nov 25 '09 at 18:35

Weird behavior like this sometimes is the result of something below the UNIX-level operating system on your Mac. Try resetting the PRAM.

When you start your computer next time, hold the Command, Option, P, and R keys until the screen goes black again and you hear the chime. Some people hold these keys until the computer has rebooted 2 or 3 times. When you feel your PRAM is sufficiently zapped, release the keys and let your computer resume its normal boot routine.

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hmmm... what information am I going to lose if I do this? it sounds risky. –  Jason S Nov 25 '09 at 1:30
    
The linked document tells you what all will be reset. –  Chris Johnsen Nov 25 '09 at 2:53
    
No user data is lost by a PRAM reset. –  jweede Nov 25 '09 at 17:20

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