Anyway to reinstall a clean Mountain Lion without erasing my personal data? Actually I really need a clean ML on my Macbook, will the Internet Recovery function delete the system folder (not user folder) and replace a clean installation to it?

I need a clean system with no third party software installed and I need to keep my personal folder (I have almost 800GB of my data in my harddrive and I currently have no space to backup my data using Time Machine)

Thanks.
A clean install is just that - it wipes out everything.

You can't do an "in place" clean install (as far as I'm aware). Even if developers wanted to provide it it would be a nightmare. I'm not just blowing it out of proportion (I'm a developer) - it would be a nightmare.

PRIOR TO ANY OF THIS MAKE A FULL SYSTEM BACKUP. Hard drives are cheap. If you can't afford a hard drive for backup, then DO NOT ATTEMPT THIS - NO SERIOUSLY. AND WHEN I SAY SERIOUSLY I MEAN SERIOUSLY SERIOUSLY.

That said, you CAN do a reasonable clean install and still maintain MOST of your information. Here's how:


Create a bootable DVD, flash drive or hard drive with the ML installer.

1a. Make sure it really is bootable!
Back up your personal data. (and any other users)
Back up your applications.
DO NOT BACK UP system info (this is the downside). Note that some applications put info in weird or unusual places - you may have to reinstall that software.
Reboot the system using the DVD, flash drive or hard drive.
Run the ML installer.
Copy all the user data and applications back.
Determine what no longer works correctly and reinstall those applications (yes - seriously NOT fun).


I did this with Lion (but not ML) but AFAIK it should work.

Clean installs "break" applications (many install libraries to work correctly or create 'hidden' directories).

Good luck (and remember: FULL SYSTEM BACKUP FIRST)