My Mac has gotten pretty dirty from all the stuff I've installed and the files I have accumulated these past months. I have tried reinstalling by holding Command-R and following the process. However, doing so has not cleaned up my file system. In fact all it seems to have done is broken some of my already installed programs (e.g. Xcode and MacPorts). Is there a way to reinstall Lion so that it will behave like its just been taken out of the box?

I have previously been an Ubuntu user, and in Ubuntu I think I was presented with the option of scraping the existing file system when I do a reinstallation.

  • So, if I understand correctly, you want to reinstall Lion but keep all your files and folders? And which process have you followed already? – Michiel Jun 18 '12 at 7:41
  • @Michiel No, I want all files and programs to go away. I am afraid that if I blindly delete stuff, I might delete files that are essential for reinstallation. Also sometimes when I manually delete files, I'm not sure if I have deleted all files related to the program. – math4tots Jun 18 '12 at 8:37
  • So, all you want is a 100% clean OS and hard drive? – Michiel Jun 18 '12 at 8:39
  • @Michiel Yes, I dont want any previously saved or installed files to survive – math4tots Jun 18 '12 at 9:41

The different thing to try after booting in to Recovery Mode is selecting the "Disk Utility" program first in order for you to erase your existing OS X install.

  1. Once Disk Utility is open you can select the Macintosh HD or so named hard drive where your existing OS X install is at, then erase the selected drive from with in the Disk Utility.

  2. Quit Disk Utility, and then you should be at Mac OS X Utilites window again as pictured below. Then from there select "Reinstall Mac OS X" as was done before.

  3. This procedure should allow a clean install of OS X, as opposed to a re-install over an existing copy of OS X.

Mac OS X Utilites Window from Lion Recovery Mode


Since Lion doesn't come with a physical installation disk, Apple has invented a way to install Lion over the internet. Apple has dedicated a whole topic about this on their support pages but I found the information there rather unclear.

Instead, I can recommend you this tutorial by MacWorld. It describes everything you need to clean your entire Mac and reinstall Lion in order to get a machine like it was just when you unpacked the device.
Good luck!

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