Upgrading from Mac OS X Snow Leopard to Lion: Installation guide

Not everyone who supports Macs in the enterprise is a Mac expert. This step-by-step installation guide includes tips and recommendations for the download-only upgrade to Mac OS X Lion.

With the recent release of Lion, I'm sure most of you are wondering what to expect. Team Cupertino changed the game this time around by providing its next major release as a download-only upgrade. How is this going effect your upgrade process? More importantly, how should you prepare? Well don't fret, I've got your back with this Mac OS X 10.7 Lion quick start upgrade guide.

This guide will focus on getting a typical Mac that meets recommended system requirements ready for a standard download and upgrade of Lion. So let's jump right in.


First we need to determine if the Mac(s) being considered for upgrade are going to meet Lion's minimum system requirements. Apple suggests that you have:

  • Either Intel Core 2 Duo, Core i3, Core i5, Core i7, or Xeon processor types;
  • 2GB of RAM;
  • Mac OS X 10.6.6 with the App Store installed;
  • At least 4 GB of additional disk space available; and an internet connection. This excludes a couple of early Intel based Macs, such as the first generation iMac and Mac Mini; however, if you purchased a Mac on or after 2006 your machine should support Lion.

To determine if you have the suggested system requirements, open up the About This Mac pane by clicking on the Apple Icon in the Menu Bar. Then select About This Mac. Here you will see your processor type, system allocated memory, and the installed version of Mac OS X. If your machine is running Mac OS X 10.5 Leopard, you will be required to upgrade to 10.6.6 Snow Leopard in order to proceed.

Software compatibility

Now that we know the machine meets suggested system requirements, the next step is an important one. We want to make sure that all of the software running on the current setup is going to be compatible with Lion. As of Lion, Apple will no longer be supporting PowerPC architecture, and has removed the Rosetta emulation layer from the OS. In essence, any installed software that isn't an Intel or Universal binary will no longer work. One thing you might want to re-evaluate is what software is a priority for your users. There may be some PowerPC applications installed; however, if the user doesn't require them, then it shouldn't be a hurdle when upgrading.

The best way to find out if the software you are running is capable of working under Lion is to open System Information (formally System Profiler). System Information can be found in the Utilities folder within the Applications folder, or you can click the Apple icon in the Menu Bar, select About This Mac, and click More Info. Once open, scroll down the left hand column and select Applications. Here you will see all applications installed on this machine, their version numbers, and their type; PowerPC, Universal, and Intel. Scroll through the list and determine if there are any installed applications running as a PowerPC binary and whether or not these are applications that the user will require. Additionally this information can be found in Activity Monitor and in the Get Info pane of any installed application as well.

Backups and updates

The next step is to back up your drive and run Software Updates. I recommend running a back up before running Software Update. Though rare, sometimes an update can cause unforeseen complications or even leave your system in a non-bootable state. Having run a back up first will provide a safety net in the event something goes awry. As far as backing up goes, Leopard offers lots of options. Time Machine is by far the easiest and most effective way to back up your Mac, and the one we will use for this guide.

Plug in an external drive with equivalent disk space or greater available to the drive you're backing up and set the drive to be used as backup when prompted. This creates a full back up of all the contents of your drive and can easily be used with Lion to restore any data during or after installation. Another option is to use the Apple-supplied Disk Utility app, located in the Utilities folder of your Mac's hard drive. If you've never used the Disk Utility app, I'd recommend sticking to a Time Machine back up, since using Disk Utility requires using additional hardware. There are plenty of third-party applications such as SuperDuper! that can be used as well but suffice to say, Apple supplies an effective and easy-to-use tool in Time Machine.

Installation recommendations

Now that we have all of our ducks in a row, its time to install Lion. Apple recommends that you have 4 GB of space available for the download and install of Lion; however, I suggest that you have a minimum of 8 GB just to be safe. Upgrading sometimes leaves behind a Previous System folder that will often take up what little bit of space is available on the drive. If you're left with 1 GB or less after the upgrade, it can cause your Mac to become sluggish or unresponsive.

Apple has made the upgrade process simple enough, with one minor draw back. Downloading Lion can take some time. Lion is a 4 GB install, so it's a good idea to set your download in motion and grab some coffee. To start the process, open the App Store either by locating it in the Applications folder or by clicking on the Apple icon in the Menu Bar and selecting App Store. Purchase your copy of Lion and start your download. Once downloaded, Lion will automatically launch the installer. Follow the on-screen prompts, agree to the software license, select the destination drive for your upgrade, and click Upgrade. Once the upgrade has completed reboot, log in, and take your new OS for a spin.