According to this thread from Apple Developer Forums, an APFS volume created on macOS 10.12.1 is not mountable on macOS 10.12.2, because of the incompatible changes.

I put some important files in my external drive formatted as APFS, and now I would like to access the data. I tried this:

diskutil apfs list


sudo fsck_apfs disk1s2

And this:

diskutil apfs addVolume disk1s2 APFS MyVolume

The error message is similar to what mentioned in the above thread:

$ diskutil apfs -IHaveBeenWarnedThatAPFSIsPreReleaseAndThatIMayLoseData list

   apfs call: sizeForContainer: err=-69808="Some information was unavailable during an internal lookup"
   apfs call: freeSpaceForContainer: err=-69808="Some information was unavailable during an internal lookup"

$ sudo fsck_apfs disk1s2

** Checking volume.
** Checking the container superblock.
error: nx_incompatible_features has unsupported flags: (0x1)
   Container superblock is invalid.
** The volume disk1s2 could not be verified completely.

My questions are:

  • Is there an official utility that help me to mount the volume?
    • Or to upgrade the old APFS to the new APFS?
  • Is there any way to downgrade my macOS 10.12.2 to 10.12.1?
    • I don't have "Install macOS Sierra.app" in hand, is there any "secret" way to download a previous version of macOS? (I mean previous versions of Sierra, not El Capitan or earlier releases)
    • I don't have Time Machine backups or similar. I would like to fresh install macOS 10.12.1 on my old MacBook, mount the volume, and copy it elsewhere.


1 Answer 1


I guess you'll have to try find someone still on 10.12.1, or who has the installer.

Lessons learned:

  1. Don't use betas for mission-critical tasks.
  2. Keep installers.
  3. Keep backups.
  • Thanks for your warm suggestions! I do keep installers and that's why I need to mount the external drive! The installers are too huge so that I put all of them in the external drive! Commented Jan 3, 2017 at 16:46
  • @SiuChingPong-AsukaKenji- But if you needed to use any of the installers on a computer running a version of OS X older than Sierra…??
    – Tuesday
    Commented Jan 3, 2017 at 21:01
  • 1
    @timothymh : All my macOS devices use Sierra. When I need to use the images, I just burn them on USB thumb drive, or mount them directly as a drive in a VM. And yes, I know there's a warning saying that APFS is pre-release software, but according to my previous experience in using btrfs or ext4, there was no incompatibility problems. I trust Apple and I thought the warning was no more than a warm reminder. I was wrong. Commented Jan 3, 2017 at 23:33

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