OSX: Format an Encrypted Drive

If you need to format an encrypted disk on OSX, you’ll need to use the command line diskutil as Disk Utility won’t let you do anything with the device.

First, find the ID of the disk you wish to format, using:

diskutil list

Which will list your disks, for example I wish to format the 2TB drive, I’d use disk2

/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *250.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            249.2 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS Data                    477.0 GB   disk1s2
   3:                  Apple_HFS Scott                   522.8 GB   disk1s3
/dev/disk2
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk2
   1:                        EFI EFI                     209.7 MB   disk2s1
   2:                  Apple_HFS Time Machine            2.0 TB     disk2s2

We can then go ahead and format the drive (remember this will format your drive and remove all data from the disk):

diskutil eraseDisk JHFS+ Test disk2

Replace the label Test with the name you wish to give the new partition. After you’ve done this, you can edit the disk normally with Disk Utility.