There might be situation with FileVault where the OSX might not be booting normally or sometimes OS X does not allows you to erase or turnoff the encryption ( Performed using Disk Utility.app available with OS X installer ). This can be a problem with FileVault 2-encrypted volume which will not let you either unlock or decrypt it. In such cases the following method will help you in deleting the core storage( FileVault encrypted) volumes on the system.
To perform this :
- Connect the OS X installer USB/Disk to Mac.
- Power on the Mac.
- Hold option key on keyboard and boot into OS X Installer.
- Open the Terminal.app from Utilities in OS X installer application.
- Run the following command to get the details about the FileVault encrypted volume.
This will show detailed information about the core storage volume available on the system.Unless you have more than one volume on the OS X system which is encrypted as well, you should have only one volume listed as core storage volume under Logical Volume Group(LVG). Please refer to the below screen shot volume for identifying the LVG information.
6. Now run the below command to delete the Logical volume group from the system.
diskutil cs delete LVG-ID
The above command will delete the corestorage volume and reformat the disk as plain HFS+ volume.
7. Quit the Terminal Application , Continue with the regular OS X installation steps.