Apple’s latest version of Mac OS X, Lion, was released on the App Store today where you can buy it for £25. For most people, this is a really convenient way to buy an operating system, providing you have a fast enough internet connection, as it saves you a trip to the Apple store to buy the boxed version, which can sometimes be a pain if there isn’t one near and you have to wait for it to arrive at your home.
For power users though, being restricted to an application for an OS install is somewhat restricting, as it means that you can’t install it on to a new hard drive without first installing Snow Leopard. Don’t you think that’s a bit… backwards? I did, so instead of upgrading I chose to find a way to install it without the need for any application file. Care to know how it’s done? Let’s check it out!
What you’ll need
- A Mac OS X computer
- Mac OS X Lion from the App Store
- A USB flash drive, at least 8GB
Preparing the flash drive
To install Mac OS X from a flash drive, you’re first going to have to format the drive and restore it with the installation image from the .app file.
If the drive isn’t already formatted, then you can do this with Disk Utility in Mac OS X. Simply insert the flash drive, and select it in the left hand column of the window. With the correct drive selected (you don’t want to erase data on the wrong drive, so double check!), navigate to the “Erase” tab in the main window and format the drive as a “Mac OS Extended (Journaled)” partition.
Next, you need to restore the image from the Mac OS X Install image you downloaded from the App Store on to the flash drive. You can’t simply restore the entire .app file to the drive as it would not be bootable, so instead you need to find a .dmg image inside the file called “installESD.dmg”. You can do this by right clicking on the app and selecting “Show package contents” and then running a spotlight search within this folder.
To restore this image, go back to disk utility, and select this .dmg file as the source field. For the destination, drag in the correct USB flash drive partition you just created and let Disk Utility work its magic.
Once you have your flash drive ready, you have a bootable copy of Mac OS X Lion! To boot into the image, insert the drive into your Mac and boot up the machine whilst holding down the option (alt) key. In addition to your existing partition, you will be able to see the image you just created. Select it from the menu to boot from it.
After booting, you will have four options in a menu. If you want to do a clean install of Lion, you can format your drive using Disk Utility before installing. Otherwise, select ‘Reinstall Mac OS X’ and follow the prompts.
Using this method, I was able to install Lion on a blank hard drive without having a previous Snow Leopard installation present on my MacBook, but my Sandy Bridge iMac wouldn’t allow me to install onto a blank hard drive, so although this may not be a 100% solution, there’s a good chance that it could work on your system. Even if you don’t want to install Lion from scratch, you can still use the image as a restore disk anyway.
If you have anything to add to this post, please feel free to leave a comment or email me at johnthompson [at] zath.co.uk.