Mac OS X FileVault setup issues

So.. I decided that after numerous random issues with my iMac, I’d do the ultimate clean install, with a reformat of the drives.

Multiple problems later and much googling along with some pseudo-random banging on keys, it finally works.


My initial goal was thus:

  1. Reformat my Fusion drive (stock 128 GB SSD + 1TB spinner)
  2. Enable FileVault

Simple enough, right?

Well, #1 didn’t go so well — Disk Utility would hang whenever I’d click the “format” button, with no error given or warning. I left my computer overnight to see if Smarmy (that’s my computer’s name) would wake up and heal itself.. and nada.

Ultimately, I had to pop open the Terminal and using diskutil, I saw this error:

Error: -69879: Couldn't open disk

Okay. Hmm. Apparently there’s a mismatch in the drive details between the SSD and the spinner, PLUS being a CoreStorage volume, I needed to run a different set of commands. This article helped: StackExchange: Deleting a partition in Disk Utility fails

Here’s what fixed it (help credit to Mac OS X Hints):

  1. diskutil coreStorage list
  2. diskutil coreStorage delete [Logical Volume Group Name]
  3. diskutil coreStorage create [ArbitraryName] [SSD DATA Partition] [Spinner DATA Partition]
  4. diskutil coreStorage createVolume [copy/paste UUID from previous output] jhfs+ [ArbitraryDriveName] 100%


Here’s what my actual commands looked like:

diskutil coreStorage list
diskutil coreStorage delete iMac\ Fusion
diskutil coreStorage create iMac\Fusion disk0s2 disk1s2
diskutil coreStorage createVolume 11111111-2222-3333-4444-555555555555 jhfs+ Macintosh\ HD 100%

This yielded a fresh, clean partition.

Now, install Mac OS X, log in, turn on FileVault.. easy, right? Well… no.

Upon turning on FileVault as instructed in the Apple KB , the reboot resulted in a big “No Entry” sign


Not helpful, Apple.

So I try to run Disk Utility first aid on the drive.. another unhelpful failure.

Popping back into terminal from the install tools.. I see that the drive is still locked. This makes sense, as I haven’t gotten to the authentication page to decrypt the disk.

diskutil coreStorage unlockVolume Macintosh\ HD

Quit Terminal, back to Disk Utility — unmount disk and first aid.. issue finally fixed.

Finally reboot, choosing the “Macintosh HD” startup disk and everything works fine.

NOTE: I would allow the system to finish the disk encryption process before restoring files, etc — it’ll be a LOT faster with an empty disk rather than encrypting all your files alongside converting your disk.


Ultimately, I don’t know why I was having issues and the rest of the internet didn’t seem to be but hopefully this will help you as well.