My preferred method: Clean install MOUNTAIN LION from a clone with prior initialization of the main hard disk and data recovery and settings with "Migration Wizard"

If you are an avid reader of OS X Easy, you already know that I highly recommend to create a clone on an external hard drive (see page dedicated to "Backup and clone OS X"). This clone allows you to start a completely identical backup your hard drive / master volume. This is an excellent insurance when your main OS X volume is broken and no longer want to start, and / or if your primary hard drive had to give up the ghost.
But the clone has other virtues. Due to the disappearance of the installation DVD, why would not use the clone as MOUNTAIN LION media to install on the hard disk / volume dedicated? Rather than annoy to go through a USB or a DVD? I see at least four reasons to use this simple, reliable and practical method to install MOUNTAIN LION:
- It's easier and faster to boot from an external hard drive on a USB drive and a DVD.
- This avoids complicating their lives if necessary to re-install MOUNTAIN LION. The installer MOUNTAIN LION being "warm" in the "Applications" folder on the clone, just start on the clone and run the installer to reinstall MOUNTAIN LION on its hard drive / master volume. No need to download again MOUNTAIN LION on APP STORE, and no need to make a bootable USB drive or an installation DVD.
- This eliminates the need for the Recovery HD partition (see "Recovery HD") which is, in my opinion, a wheel ultimate fallback, nothing else.
- You can make this method a "clean install" (clean install) with ease.
How to proceed? It must of course have a bootable clone on another hard drive.
a) Purchase and download MOUNTAIN LION on APP STORE.
b) Once the download is complete, the installer is in your "Applications" folder.
c) Update your clone, so that the installer is also present in the "Applications" folder on the clone.
d) Start the clone.
e) Launch "Disk Utility" and proceed with the hard disk initialization / main volume, where you will install MOUNTAIN LION (see tip "Initialize, format and partition the disk" for more information on this operation). If you have the interest, you can also make a partition on your main hard drive and dedicate a partition to MOUNTAIN LION (see above section on partitioning).
f) Once your hard drive / master volume completely erased, run the installation from the MOUNTAIN LION downloaded installer (which is therefore now well into the "Applications" folder on the clone).
g) Follow the installation procedure by selecting well your main drive (or partition dedicated) disk, where the MOUNTAIN LION to be installed, then click "Install."

h) The installation starts. Your Mac will re-start by itself, do not interrupt the process and let it go until the end. Once MOUNTAIN LION, you need to set (as always) some windows:

i) "Migration Assistant" then launches AUTOMATICALLY. You will therefore be able to get on all your data, applications and settings. Select "From another disk" in the first window that will appear on the screen, then select (in the window that follows) your clone (this is where all the data is to be transferred), then make sure that all boxes are ticked in the window that then opens. Click on each small arrow to the right to move to the next step.
NB: It is also possible to select the disk dedicated to "TimeMachine".

j) The data transfer can be longer or shorter depending on the individual configurations. Do not interrupt the process.

k) Once the transfer is complete, it is you are under MOUNTAIN LION. Set the latest windows as you like: you can enable or disable location services (personally I activated because it allows some applications require to determine your location, run), and choose to set the time zone automatically.