How to Do a Clean Reinstallation of OS X Lion

Being in the business of testing and tinkering with computers, it’s no surprise that I have to format and reinstall once in a while. This habit is closely associated with Windows machines, which are larger targets for viruses and other malicious software. Contrary to popular belief, there are occasions where you might find yourself needing to do this with a Mac running OS X. Sometimes, bit rot can set in and things just stop running the way they used to. Habitually tinkering with drivers and other vital components of your system doesn’t help the longevity of your performance, either.

So, if you find yourself in a situation where simply reinstalling OS X Lion over itself doesn’t resolve the issue, it may be time to consider erasing the drive and starting from scratch. This can be a pain in the neck, but thankfully it isn’t quite that bad. OS X Lion has given users the added bonus of not having to scramble around for installation discs. Aside from support software such as iLife, the OS itself is actually baked right into your hard drive on a hidden partition. This works for a lot PCs configured by major distributors that want to save money on providing customers with restore discs.

So, how do you do a clean reinstall of OS X Lion? The process is very similar to restoring, with a just a few extra steps.

How to Do a Clean Reinstallation of OS X Lion

Here’s what you need to do:

  • Back up important data to an external drive. You can do this in many different ways.
  • When rebooting, hold Command+R.
  • Select Disk Utility.
  • Hit Continue.
  • Select the primary partition (Usually Macintosh HD) under the hard drive.How to Do a Clean Reinstallation of OS X Lion
  • Go to Erase tab.
  • Select Erase….
  • Confirm Erase.
  • Click the red X in the upper left corner (Close the window).
  • Select Reinstall Mac OS X.
  • Hit Continue.
  • Select Continue in the pop-up pane that appears.
  • Agree to the terms.
  • Select the primary drive you just erased. This is usually Macintosh HD unless you gave it a custom name.
  • Enter your Apple ID (the one you used to purchase Lion or register your Mac with Lion pre-installed).
  • Let it do its thing. Grab a snack.
  • Choose your country or region and select Continue.
  • Select your keyboard layout.
  • Select Don’t Transfer Now and Continue.
  • Log in using your Apple ID.
  • Confirm your information. This will be used to update registration of the Mac.
  • Click Continue.
  • Enter your name, and an account name that will be used as the name of your home directory.
  • Click Continue.
  • Pick your avatar. You can opt to take a photo using the camera (if one exists) or an icon.
  • Select Start Using Lion.
  • You’re Done!

Once you’ve done this, Lion should be up and ready to go. If you want to reinstall your iLife applications, you can do so using the disc provided with your Mac. Make sure that you check for updates first and foremost, as the installation doesn’t include the latest updates released since your system was manufactured or upgraded to OS X Lion.

There is a lot of controversy out there as to whether or not you need to do a clean install of OS X, ever. While there may be ways to resolve ongoing issues, there are plenty of good reasons to do this. No system is really safe from bit rot, and occasionally, it’s easier to start fresh than dig around and attempt to find the cause of the problem.

For me, it’s much easier to work on any OS if it’s clean. With literally dozens of apps being installed and/or uninstalled from my system on a monthly basis, it’s one of those processes that makes sense after a while — especially when things begin to slow to a crawl.

Additional Notes

Be Prepared to Reinstall Applications
The process of doing a clean install means literally wiping everything you have on the primary drive partition. Everything you have on the drive, including applications, will be lost. If you purchased the majority of your apps through the Mac App Store, this shouldn’t be a big problem at all as reinstalling these applications is a matter of a click of the mouse. For other programs, you’ll need to go through installation all over again.

Make Sure You Need to Do This
There really aren’t a lot of cases where a clean install is warranted. In fact, a lot of people out there (including many experts) would argue that this process isn’t even necessary. As noted previously, sometimes it’s just easier for the individual to start from scratch.

Be Committed
Once you erase the primary partition, there is no turning back. Make sure that you’re committed to going through with the process from that point forward. You can still do a traditional reinstallation that isn’t damaging to your existing files and settings by bypassing the Disk Management portion of the process.

Make Sure You Back Up Before Any Reinstallation Process
Even if you’re just doing the simple reinstall, you should back up your data. Just as a light may suddenly fail when you switch it on, a tedious operation being carried out by your hard drive may bring to light an issue that has been building over time. Besides, it’s a good idea to back up your important data, anyway.

Take Inventory of Your Existing Software
If you’re in a situation where a clean install looks like the best solution, it might be a good idea to take inventory of your software and try to determine what you do and don’t actually need. It’s easy to pick up tons of apps for various things like hard drive management, memory optimization, and other clutter over time. Take note of each app and/or system pane you have installed and determine whether or not you actually need it. The less you have running at any given time, the more clock cycles you can free up for other programs you do need open.

After all, the most important result of any clean installation is to reduce the clutter and free up system resources.

Consider Making an Installation Disc

Craighton Miller, a writer here on LockerGnome, wrote a detailed step-by-step guide outlining how you can create an installation disc for OS X Lion. This is a great way to keep a long-term copy of the OS in the event that your recovery partition becomes corrupted or otherwise compromised.

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