So I got a new MacBook for work and I didn't realize upon next reboot, the enterprise profile had mandated FileVault encrypt the start up disk, and Apple had recommended an upgrade to macOS Sierra at the same time! You can imagine triggering both simultaneously upon reboot didn't go well at all!

FileVault vs Sierra Update

Here is what happened:

  1. I triggered an OS update from the Install Sierra app. Rebooted.
  2. Greeted with prompt to enter my admin password for FileVault to start. Entered.
  3. Wrote down the FileVault Recovery Key, and closed the FileVault message that I could continue to use the machine while FileVault worked in the background.
  4. Then the macOS Sierra update app ran, and from here on it's a blur - the machine rebooted but went to macOS Recovery mode instead (read more About macOS Recovery).

macOS Utilities Recovery Mode Reinstall macOS

  1. Choosing Reinstall macOS from the Recovery menu has the start up disk greyed out - because FileVault encryption is in progress.
  2. DiskUtility does not have any options to check the status or progress of FileVault.

Perhaps if I had let Step 3 above continue without closing the message, it would have completed and then only gone on to Step 4 and begun the upgrade process. Who knows?

The Fix - Let FileVault Complete

The solution is given by the guru "mewiki" over at the Apple forum post, Unable to Install OS X El Capitan FileVault conversion in progress.

  1. In Recovery mode, run Terminal from the menu (if it doesn't start, hold Cmd + R during boot).
  2. In terminal, type diskutil cs list. I got the last screen below, and the key is that Conversion Progress: Paused
diskutil cs list
        +-> Logical Volume XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
            ---------------------------------------------------
            Disk:                  disk1
            Status:                Online
            Size (Total):          249779191808 B (249.8 GB)
            Conversion Progress:   Paused
            Revertible:            Yes (no decryption required)
            LV Name:               Macintosh HD
            Volume Name:           Macintosh HD
            Content Hint:          Apple_HFS
            LVG Type:              Sparse
  1. I re-started the conversion by typing /usr/libexec/corestoraged
    • In mewiki's guide, he first searched for the correct folder, with file / -name 'corestoraged',
    • But instead, I'm assuming it's in the same location for all of us...
  2. That terminal will now be busy, so open a new Terminal.
  3. And check the conversion progress, with diskutil cs list:
    • Mine started with just a percentage, e.g. Conversion Progress: 62%,
    • Then it re-started the percentage, but this time, optimizing, e.g. Conversion Progress: Optimizing 82%
diskutil cs list
        +-> Logical Volume XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
            ---------------------------------------------------
            Disk:                  disk1
            Status:                Online
            Size (Total):          249779191808 B (249.8 GB)
            Conversion Progress:   62%
            Revertible:            Yes (no decryption required)
            LV Name:               Macintosh HD
            Volume Name:           Macintosh HD
            Content Hint:          Apple_HFS
            LVG Type:              Sparse
  1. When it has completed optimizing, reboot...
  2. And if all is well, you'll be able to continue the Sierra installation!

Conclusion

There are real apple geniuses out there... and they don't work for Apple. Apple really left out this scenario in the macOS Recovery options - one should be allowed to check on the progress of FileVault, and either finish it or undo it - without resorting to console commands!

Whew!