Editor's note: This article is the first in a series of upcoming articles on installing Mountain Lion. We'll publish a complete guide to the new version of OS X once the update becomes available.
The word on the street is that Apple has released to developers the golden master of Mountain Lion (OS X 10.8)--the final non-public version. And that means the official public release of Mountain Lion isn't far off. Speculating on the specific date of release makes for interesting discussion--all Apple has said publicly is that the new version will arrive in July--but those aiming to upgrade as soon as the new OS drops have more pressing matters: Getting their Macs ready for Mountain Lion.
As with Lion (OS X 10.7) last year, Apple is advertising Mountain Lion as dead-simple to install. But as with every major upgrade to OS X, there are a few things you can do before Mountain Lion is released to ensure that your Mac is ready for the new release.
What you need
Apple says Mountain Lion requires one of the following computers, already running OS X 10.6.8 or any version of OS X 10.7:
MacBook (Late 2008 Aluminum, or Early 2009 or newer)
MacBook Pro (Mid/Late 2007 or newer)
MacBook Air (Late 2008 or newer)
iMac (Mid 2007 or newer)
Mac mini (Early 2009 or newer)
Mac Pro (Early 2008 or newer)
Xserve (Early 2009)
(Note that while the above computers can install Mountain Lion, some features, such as Power Nap, AirPlay mirroring, and AirDrop, have stricter requirements.)
Apple also says you need 2GB of RAM (memory), although in my experience, you'll enjoy better results with at least 4GB. If you have only 2GB installed, you might consider a hardware upgrade before installing OS X 10.8. A word of advice here: If you don't buy your RAM directly from Apple, be sure you get RAM that's specifically designed for use in Macs. Some third-party RAM that's not up to Apple's specs will cause problems when you upgrade your OS. Most reputable vendors will make it clear which RAM they offer is specifically compatible with Macs.
Similarly, Apple recommends having at least 8GB of free space on your Mac's drive, but I recommend playing it safe by aiming for 15GB or more--the Mountain Lion installer itself is over 4GB and you'll need some room for temporary files. You may also find, especially if you're upgrading from Snow Leopard, that some of Mountain Lion's features require more "everyday" free space, as is the case in Lion. If you need to free up space on your drive, you can use a utility such as WhatSize or GrandPerspective to help you find big files you can get rid of; and we recently provided some specific suggestions for freeing up drive space.
Not sure which Mac you own or how much RAM or free drive space it has? Choose About This Mac from the Apple Menu, and then click More Info. In Lion, the resulting window displays your computer model and year/version; click the Storage tab to view your drive's free space, and click Memory to check its RAM amount. In Snow Leopard, you get a System Profiler window--select Memory to check the RAM amount; select Serial-ATA, and then select your drive's name on the right, to see your free drive space.
Unfortunately, Snow Leopard's System Profiler window doesn't display your Mac's actual model year/version. What it will show you, in the Hardware Overview screen--click Hardware on the left--is a Model Identifier, which consists of a Mac name and two numbers separated by a comma. For example, my Mid 2010 iMac's model identifier is iMac11,3. You can then use the excellent Mactracker (Mac App Store link) to find your official Mac model name: Just launch the app, click All Models on the left, and then type your Mac's model identifier in the search field at the bottom of the Mactracker window; the list of Mac models will be filtered to display just yours.
The requirement that your Mac be running OS X 10.6.8 or any version of OS X 10.7 is also important. The main reason for this restriction is that, like Lion, Mountain Lion will be available only via the Mac App Store--the Mac App Store requires Mac OS X 10.6.6, and OS X 10.6.8 provides a number of enhancements that make upgrades to 10.7 or 10.8 go more smoothly. In addition, Apple recommends that you install the very latest updates to Snow Leopard or Lion before upgrading to Mountain Lion, so be sure to check Software Update for any available updates. (See "Pre-install checks," below.)
What if you've got an otherwise compatible Mac that's still running Leopard (OS X 10.5)? The easiest option is to purchase Snow Leopard for $29 and install it now, then upgrade to Mountain Lion when it's released. You'll still be paying less than $50 for a huge OS upgrade. If that isn't an option for you, for whatever reason, stay tuned--we'll explain how to install 10.8 over Leopard, assuming you have the right to do so, much as we did with Lion last year. (If you've got one of the two Mac models that originally shipped with OS X 10.4 Tiger and support Mountain Lion, and you're still running Tiger, you definitely want to go the Snow Leopard -> Mountain Lion route--the alternative is very messy. Also, wow.)
Finally, although it's not a requirement, if you've got a desktop Mac, I highly recommend picking up Apple's Magic Trackpad if you don't already have one. The systemwide gestures introduced in Lion last year are only going to become more pervasive as OS X evolves, and you likely won't enjoy the full benefits of Mountain Lion without a trackpad. (MacBook users, of course, all have a trackpad already.) I personally prefer a mouse or large trackball for general "mousing," but I keep a Magic Trackpad within reach, as well, just to take advantage of OS X's gesture-based features. I call it my Magic Gesturepad.
While Apple describes the process of upgrading to Mountain Lion as a simple download and install, those of us who've been doing this for a while know that a major OS update is never that simple. Perform the following tasks before the upgrade and you'll have a much better chance of actually enjoying a pain-free experience.
Make sure your Mac's startup drive is in good health: To do so, open Disk Utility (in /Applications/Utilities), select your startup drive in the list on the left, click the First Aid tab to the right, and then click Verify. If Disk Utility finds problems, you'll need to boot from a different volume to perform the actual repairs using the Repair Disk button. If you're upgrading from Lion and your Mac can use Lion Recovery, you can boot into recovery mode (by holding down Command+R at startup) and use Disk Utility from there; alternatively, if you created a bootable Lion-install drive for older Macs or for newer Macs, or created a separate Lion Recovery drive, you can boot from that drive and use Disk Utility. If you're upgrading from Snow Leopard, you can use Disk Utility when booted from either your Snow Leopard Install DVD or the OS X install DVD or thumb drive that shipped with your Mac. If you're feeling especially cautious, you can also opt to run Apple Hardware Test.
Back up your Mac, and test that backup: Let me say that again: Back up your Mac, and test that backup--before installing Mountain Lion. (See our article on Mac backup plans for more info on backing up your Mac.) I personally recommend creating a bootable-clone backup (using SuperDuper or Carbon Copy Cloner) for the task, although a Time Machine backup will do, as well. To test a clone or other bootable backup, use the Startup Disk pane of System Preferences to boot from the backup drive. To test a Time Machine or other non-bootable backup, try restoring several files--both older ones and newer ones--to make sure you can recover your data should disaster strike.
Snow Leopard users should disable FileVault: If you're upgrading from Snow Leopard (OS X 10.6) and you're using FileVault, OS X's built-in account-encryption feature on any of your Mac's accounts, I recommend disabling FileVault before upgrading to Mountain Lion. Mountain Lion, like Lion before it, uses a different (and much-improved) approach to encryption, called FileVault 2. Apple says you can keep using the Snow Leopard implementation for previously-encrypted user accounts, but FileVault 2 is the better way to go, and what better time to make the switch than now? (As I noted in my Lion-upgrade guide last year, I also prefer to not test Murphy's Law by risking any incompatibilities between the two versions of FileVault.)
Disable third-party disk encryption: If you're using third-party full-disk encryption software, you may want to temporarily disable that encryption before upgrading your Mac's OS. Most of these products interact with your drive and the OS at a low level, and an incompatibility with Mountain Lion could leave you unable to boot your Mac or, worse, unable to access your data at all. Once Mountain Lion is up and running and you've verified (with the developer) that your encryption software is compatible, you can re-enable encryption. However, given that FileVault 2 also encrypts your entire drive, you might consider this an opportunity to migrate to FileVault 2.
Run Software Update: To be sure you're running both the latest version of Mac OS X--version 10.6.8, for example, includes fixes to Snow Leopard that are required for upgrading to Mountain Lion--and the latest versions of any other Apple software that might be affected by the upgrade, you should run Software Update (from the Apple menu). You should also check for updated firmware for your particular Mac model.
Check for Mountain Lion-compatible updates to third-party software: As with any major upgrade to Mac OS X, you'll likely find that some of your third-party software needs to be updated to work with Mountain Lion. If you take some time to check compatibility before installing OS X 10.8, you'll be in a position to get up and running immediately, rather than being frustrated by your favorite apps and add-ons not working.
To check app compatibility, you can visit each developer's website, but I recommend first checking RoaringApps' growing list of Mac software and Mountain Lion compatibility. (The list shows both Lion and Mountain Lion compatibility--be sure to look at the Mountain Lion column.)
If an app has an update available, you'll want to download and install that update. For apps you've obtained via the Mac App Store, this is as simple as launching the App Store app, clicking the Updates button in the toolbar, clicking Update All, and providing your Apple ID and password when prompted--this will download and install all available updates at once. For non-Mac App Store apps, you'll need to manually install updates. Some apps provide a built-in update feature (often accessed by choosing Check For Updates from the application's Application Name menu or its Help menu); for those that don't, you'll need to visit the developer's website.
The biggest offenders here--in terms of being incompatible with Mountain Lion--will be programs and system add-ons that integrate with (or hack) OS X at a low level. Kernel extensions, for example, are notorious for being incompatible with major new versions of OS X, but you may also find that utilities that tweak the Finder, add-ons that enhance Mail, and other plug-ins and "enhancers" won't work under Mountain Lion, even if they worked fine under Lion. (This will be a bigger issue for people upgrading from Snow Leopard.) So be sure to check vendor websites for OS X 10.8-compatible updates for your favorite software before upgrading. (Don't forget to check third-party System Preferences panes and Mail add-ons.) If it turns out that a particular bit of software is incompatible with Mountain Lion and doesn't have an update available, uninstall or disable it until a compatible version is released.