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Old 01-15-2019, 07:09 PM
wildthing wildthing is offline
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Join Date: Dec 2011
Posts: 36
Disk Utility First Aid says 'invalid btn_btree.bt_key_count' on APFS volume

Before APFS, when I did a SuperDuper backup I used to regularly click Repair Disk in Disk Utility to check the health of my drives and see if anything needed repairing.

After updating to APFS I no longer do this, because I got the impression APFS has many integrity checks and other features that make that unnecessary.

However today, just for fun I tried running "First Aid" in Disk Utility on my primary drive, which has been on APFS for some time. To my surprise it showed an error:

  Verifying file system.
  Volume could not be unmounted.
  Using live mode.
  Performing fsck_apfs -n -l -x /dev/rdisk1s1
  Checking the container superblock.
  Checking the EFI jumpstart record.
  Checking the space manager.
  Checking the space manager free queue trees.
  Checking the object map.
  Checking volume.
  Checking the APFS volume superblock.
  The volume [redacted] was formatted by hfs_convert (748.21.6) and last modified by apfs_kext (945.230.6).
  Checking the object map.
  Checking the snapshot metadata tree.
  Checking the snapshot metadata.
  Checking the extent ref tree.
  Checking the fsroot tree.
  error: btn: invalid btn_btree.bt_key_count (expected 8569255, actual 8569307)
  fsroot tree is invalid.
  The volume /dev/rdisk1s1 could not be verified completely.
  File system check exit code is 0.
  Restoring the original state found as mounted.

  Operation successful.
When I googled this error, most of the replies advise to boot into Recovery Mode and run First Aid to repair the volume.

As suggested I booted into Recovery Mode and ran First Aid - but it just reports the same error again, and gives no sign of attempting to repair anything.

So my question is: do I need to worry about this error? Or, based on the fact that First Aid says "exit code is 0" and "Operation successful", and does not attempt any repairs, do I not need to worry about it?

I realize this is not strictly a SuperDuper question - but I think you've acquired some knowledge of APFS, so I was hoping you might have some insights

Thanks for any pointers.

Last edited by wildthing; 01-15-2019 at 07:11 PM.
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