Format Filevault Encrypted HD

Discussion in 'OS X Mountain Lion (10.8)' started by wngraham, Sep 26, 2012.

  1. wngraham macrumors regular

    Jun 8, 2006
    Nashville, TN
    I've decided to do a fresh install of Mountain Lion on my MacBook Pro (using a USB flash drive with the install disk on it).

    My only concern is my harddrive has been encrypted using Filevault 2. Will this pose any issues? My plan was to boot into the USB drive then format the internal HD using Disk Utility, just as I always have when previously doing fresh installs.

    Do I need to decrypt the disk first?

    Any help or advice will be greatly appreciated.
  2. EmpyreanUK macrumors regular

    Mar 6, 2011
    You can indeed format an encrypted drive using the disk utility included in the OS X installer.

    Before you're able to re-partition/format the drive, you have to unlock it first. When in Disk Utility, click on the drive you're planning to format, and then choose the toolbar option that says something along the lines of 'Unlock' or 'Verify'. You'll be issued with a password prompt: enter the password, and the drive will then mounted normally so that you're able to re-partition it, ready for the OS X installation.
  3. richardsim7 macrumors regular


    Oct 17, 2007
    ...and if you don't know said password?
  4. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    If you are booted from a USB key you can just select the drive name at the top (like Seagate 500GB) and erase the entire disk from there. No PW is needed.
  5. ikev85 macrumors member

    Mar 6, 2012
    You can also open terminal type

    sudo diskutil cs list

    find the UUID at the top and type

    sudo diskutil cs delete <UUID>
  6. Bear macrumors G3

    Jul 23, 2002
    Sol III - Terra
    You don't need to decrypt the disk. You do want to erase the whole disk and not just the partition. After that the installation should work as normal. You will then need to enable FileVault 2 after the installation is finished.

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