Getting Started: How to Perform a Clean Install of Mac OSX Mountain Lion

By January 28, 2013 Programming No Comments

Shortly after Dev Bootcamp, I was ready to start doing my own side projects, namely a platform for turning stacks of lab test papers into an online dashboard of coherent health information. Unfortunately, I was running into problems associated with setting up a Postgres database in a development environment, and a mentor said it may be due to problems with Homebrew and that fixing them would “level you up in sysadmin skills”.

I thought upgrading my Macbook Air’s operating system from Lion to the Mountain Lion would fix the issue.

It didn’t, and I ended up being unable to do basic things like run Rspec to test my Rails applications. Because of that…

I decided to do a completely clean install of the OS X Mountain Lion, which would save time and allow one to:

  • develop an understanding of what goes into a properly working development environment
  • not worry about patching up an unknown number of problems that could occur at any point down the road

Although “leveling up” in system administration skills would help any developer, I’m looking to maximize my time spent learning skills more directly related to web development. Being sidetracked by tangential issues can be discouraging, especially for beginners who need to learn core skills first. The idea is to maintain long term motivation with quick wins, only then following with increasing depth of technical knowledge in supporting, non-mission-critical areas such as system administration.

Without further ado…

How to Do a Clean Install of the Latest Operating System for Mac

Total Time: 1:00-1:30 hours.

Tools needed:

  • USB thumb drive with 8GB or more storage
  • hard drive, thumb drive, or online “cloud” storage account with enough space to store all system files


  1. Download, but do not install, Mountain Lion from the Mac App Store. If you already upgraded to Mountain Lion, re-download it. [15-30 min]
  2. Install the latest version of Lion DiskMaker: [1-5 min]
  3. Create a bootable install drive with an empty 8GB USB drive by following instructions on Lion DiskMaker [15-20 min]
  4. Save all system files. With a clean install, everything will be erased and Mountain Lion will be installed in its place, so at minimum, save your documents, media files, and other important files. I saved a copy of everything on my hard drive to Dropbox, thinking it would be cool to use a hardware-free approach, and it took 3 days to sync to the cloud! Next time, I would opt for a hard drive or large thumb drive for near-instant data backup.
  5. Reboot Mac and Rewrite the Hard Drive [30 min]
  • Restart your computer and hold down “Option” key on reboot. This will lead you to the menu.
  • Select “Mac OS X Installer” from the menu.
  • Select “Disk Utility” and choose the hard drive to be formatted on the left hand side. Click the “Erase” tab. Click on “Format” and select “Mac OS Extended (Journaled”).
  • Click the “Erase” button. At this point, consider your data gone forever unless you saved it elsewhere. Beware!
  • Exit out of “Disk Utility”. In the menu, choose the “Install Mac OS X” option. Install Mountain Lion onto the newly reformatted hard drive.

The computer will reboot and you will have a clean install of Mac OS X 10.8!