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Your Mac Won’t Reboot when Installing Mac OS X Lion – Reset Your PRAM

Mac OS X LionOverseeing the Mac OS X Lion upgrade of all the Macs at Work, I’ve seen the Lion installs generally be the easiest OS X Upgrade ever. But I wasted almost two days upgrading one of our Mac Pros. We have several Mac Pros with the same configuration, 2008 Vintage Dual Quad Core’s with Software RAID 1 drives.

The first ones we did had no problem at all. But one of them gave the dreaded multi-lingual kernel panic display on the initial reboot after the user ran the Lion Updater.Multi-Lingual Kernel Panic Screen of Death

At first I suspected the fact that the unit had Software RAID as the initial Googling showed that many folks had similar issues with Software RAID. When I booted from the Lion boot DVD I had created from the Lion installer download and ran the Disk Utilities, it reinforced the assumption that there was some issue with Lion and the RAID as the Disk Utility wouldn’t do anything with the disks (the various First Aid buttons were greyed out). But then I had some similar problems with the Snow Leopard DVD Disk Utility, so I assumed that the disk[s] had gotten corrupt. I spend most of the next day using Disk Warrior to recover the disks, tried various attempts of using Disk Utility and command line diskutil to make the RAID work with Lion.

Of course the itterations were long since it required reboots from DVD, etc. Eventually I got some new drives and did a totally fresh install and would just end up with the Grey Screen with the circle with a line thru it instead of the Apple Symbol on boot.

That was when I realized it probably wasn’t the RAID issue (also found plenty of folks including ourselves where Lion and Software RAID did work). So some different Googling found one article that mentioned resetting the PRAM. And of course, that worked. I had previously done the “hold down the power button till the power led blinks rapidly and hear the reset tone” assuming that reset everything that needed to be reset on modern Macs.

I haven’t had to CMD-OPTION-P-R keyboard chord reset the PRAM in ages. I had thought that it was no longer a thing with Modern Macs and the push and hold the power button had replaced it. But low and behold what was need the was the old fashioned PRAM Reset.

So if you have a problem where your Mac won’t reboot after the initial install of Lion, give the old PRAM reset power chord a try.


  1. max max January 6, 2012

    OK. similar problem here. several macs updated to lion via thumb drive start up etc that went perfectly.

    Then I tried to do CLEAN Lion install as my main book was giving me various problems. could not get it to launch properly (from the Lion thumb drive) to save my life. More trouble shooting and test of different drives when PRAM issue came to light and I got it to load smoothly with alt drive. So…the original hard drive was now suspect. I go out and get new one, load it and first attempt to run Lion install and I get a hang up on install. UGHH…thought we had this beat. Then I went straight to PRAM reset again and violla….smooth install.

    So new HD is running and PRAM hint is big deal when you run into Lion on top of lion clean install and having basic launching problems. My concern is to whether or not I now have some more basic problem in the machine that is requiring PRAM resets and if it is going to become an ongoing issue, if that’s even possible and what it might portend??

    Nice article and thanks for any feedback. MS

    • Robert J Berger Robert J Berger Post author | January 6, 2012

      There doesn’t seem to be any danger doing the PRAM reset often other than the hassle and like you said the suspicion that something is bad requiring this.

      The only problem I’ve had before and after the Lion upgrade that has been causing me to do a PRAM reset has been bluetooth freezing up. It happens to me several times a month if I’m using bluetooth headset to stream music. The system thinks there is no bluetooth hardware. I find if it gets in that state I have to shutdown and do a PRAM reset….

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