I am considering upgrading my Mac to the new Mountain Lion operating system. What steps should I take to make sure the process goes as smoothly as possible?

  • Can I make this a more general question? I know that you asked a more specific question, but I think that this can be opened up to apply to all machines. Upgrading from Snow Leopard is no different than upgrading from Lion, except that you need to at least run 10.6.8. – daviesgeek Jul 26 '12 at 6:36
  • Sure, go ahead. I specified that I'm running 10.6.8 in case there were any instructions that applied only to machines running other OS X versions. Thanks. – Sam Weinberg Jul 26 '12 at 9:41

According to The Tech Scoop and Lifehacker, there are a number of things you should do before upgrading.

  1. Make sure your computer will actually run Mountain Lion. Here is a list of all the Macs that will not support Mountain Lion.
  2. Run Software Update. Go to the Apple menu > Software Update and make sure you have all the current updates installed. Make sure that you are at least running Snow Leopard 10.6.8 (as required on Apple's website).
  3. Make sure you have enough space on your drive. Mountain Lion requires 8GB of space, so make sure you at least have that amount free (preferably more though). If you don't have the space required, you can use a disk visualizer such as DaisyDisk ($9.99) or Disk Inventory X (free) or use AppCleaner to remove old, unused applications. More detailed information on that is available from Lifehacker
  4. Check that all your applications wil run on Mountain Lion. RoaringApps is the best place to check. It has a status indicator, and a feature list of what feature the application supports
  5. Repair disk permissions and disk. If you are running Snow Leopard, start from the install disc and open Disk Utility. If you are running Lion, shut down and restart while holding Command ⌘ + R (restart into the Recovery partition). In Disk Utility, click on your main hard drive and then click "Repair Permissions". When that's done, click "Repair Disk". Thanks to cksum for commenting that repairing permissions before an install is not necessary. "You don't need to repair disk permissions prior to installing Mac OS X over a previously-installed OS. The installer will do this automatically." (Apple KB doc about repairing permissions)
  6. Backup your computer. This is the most important step. If something goes wrong while installing Mountain Lion, you want to have a backup to go back to. Also, if for whatever reason you want to revert to Lion, backing up your computer will make it a million times easier to revert. The Tech Scoop recommends using Disk Utility to backup your computer. Lifehacker recommends using either Time Machine or Carbon Copy Cloner to backup your computer. My preference is Carbon Copy Cloner, freeware software for cloning a hard drive. If you want to use the other options, check out the links above. Open Carbon Copy Cloner, select the source and the target and click "Clone". Wait for it to backup your computer...

If you've completed all the above steps, your Mac is ready for Mountain Lion! Go to the App Store and install Mountain Lion.

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  • (4) is not required. All Apple installers (this includes OS X, but technically any package released by Apple) will check and repair permissions before they proceed with the actual installation. – user10355 Jul 26 '12 at 7:24
  • After a bit of searching, I found this Mountain Lion OS X App Compatibility table. Would you mind adding this to your list? – Sam Weinberg Jul 26 '12 at 10:02
  • @SamWeinberg yes, I realized late last night I needed to add that as a step. I do apologize for not adding that and making you go find it. :-) that was the exact table I was going to add. – daviesgeek Jul 26 '12 at 17:15
  • @cksum okay. I will edit that in the step, though both Lifehacker and The Tech Scoop recommended it. – daviesgeek Jul 26 '12 at 17:16
  • They are wrong in doing so. support.apple.com/kb/HT1452 "You don't need to repair disk permissions prior to installing Mac OS X over a previously-installed OS. The installer will do this automatically." – user10355 Jul 26 '12 at 22:02

In addition to the above, and over-and-above any backup strategies, if your iCal connects to any third-party Cal-Dav servers you'd be well advised to export a copy of those calendars to a .ics file first as I found the upgrade to Mountain Lion nuked all my non-iCloud calendars apart from my default Google calendar. All calendars I had linked to Google Groups got nuked too.

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On point 6. Backup your Computer of @davisgeek's answer, I'm just adding SuperDuper as a backup option. Its free and tremendously useful (Creates a bootable backup). Read about it here:


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You can't be sure:

I've had ML for almost 2 weeks like most of you. The video/sound stuttering, no sound at all, and paused video started immediately after I installed ML. In this and other forums, I shared a long list of everything I tried. I sent this list to Apple also. Since then, I've tried at least a dozen other things (from ripping out files and external devices to installiing ML on a newly-formatted external HD to...well, the list goes on and on.)...

I agree, there is something wrong with the system, it doesn't' matter what I am running! I'm glad I cloned my hard drive before all this so I can go back to Lion...

When I got Mountain Lion, the first thing I noticed was some slowness. Ok, after indexing, reboots, PRAM resets, disk permissions, etc... It is runnable, but I STILL CAN'T PLAY MUSIC ON ITUNES!!!! STUTTERS STUTTERS STUTTERS!! I FEEL LIKE I WAS DOING COOPER WITH A DISCMAN.

My hardware is a 2011 iMac with a 3.4 GHz I 7 processor, solid-state hard drive, 2 GB AMD 6970 video card, and 16 gigs of RAM. Anyone else having this. Also, the stutter under ML seems to be more frequent and more rubber banding. Not sure if that is the OS or Diablos fault


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  • I have the same iMac but not seeing that issue. – Dave Sag Aug 7 '12 at 2:34

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