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Question: Time Machine failing to complete backup - Failed to unmount local snapshot?

I have an external USB drive to which I have been doing my Time Machine Backups for about 5 years now. Recently, it started refusing to complete the backup.

When I connect the drive and choose to create a backup, it either:

  1. Stay in "Preparing backup" state for a long time and then goes back to idle (does not start the backup at all)
  2. Starts the backup, after a couple of GBs it goes back to idle (as if nothing happened)

I tried scanning the disk with

fsck
, which reported everything being fine. I have also tried multiple other solutions, icluding removing the
.inProgress
file and rebooting the mac (this one looked promising, started preparing the backup and ran for about 5/30 GB, only to stop "back to idle" then).

I do see my previous backups listed on the disk with Time Machine, just creating the new ones seems to be a problem. It should not be disk space, as there is 250GB available (and the entire Mac's disk is 64 gigs).

After the backup fails, I see in its log:

Copying items from "Macintosh HD" (device: /dev/disk1s1 mount: '/' fsUUID: 031D3803-B01C-3414-9912-9C615E0AE313 eventDBUUID: C58D9E07-C0C6-44F6-B27F-522C5C3895A7) 26 c :ERROR:-128, copy /Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/namehere/2017-11 -05-133152/Macintosh HD to /Volumes/Time Machine/Backups.backupdb/namehere/2017-11-05-133153.inProgress/FB9A54C7-8DC5-40 1C-ABE0-7131A79EF624

Finished copying items for "Macintosh HD" (device: /dev/disk1s1 mount: '/' fsUUID: 031D3803-B01C-3414-9912-9C615E0AE313 eventDBUUID: C58D9E07-C0C6-44F6-B27F-522C5C38 95A7) Time elapsed: 22 minutes, 58.000 seconds Copied 180065 items (5.69 GB) Copy stage canceled Backup canceled. Total time elapsed: 44 minutes, 26.000 seconds

After the first retry, the log looked similar (this time copied about 3 GB). Finally, trying to run the backup once again, resulted in the following log:

Running preflight for "Macintosh HD" (device: /dev/disk1s1 mount: '/' fsUUID: 031D3803-B01C-3414-9912-9C615E0AE313 eventDBUUID: C58D9E07-C0C6-44F6-B27F-522C5C3895A7) Scanning nodes needing deep traversal Deep event scan at path: /Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/namehere/2017-11 -05-191243/Macintosh HD reason:must scan subdirs|new event db| Calculating size of changes Backup canceled during preflight. Should copy 0 items (0 KB) representing 0 blocks of size 4096. 49066159 blocks available. Preflight complete for "Macintosh HD" (device: /dev/disk1s1 mount: '/' fsUUID: 031D3803-B01C-3414-9912-9C615E0AE313 eventDBUUID: C58D9E07-C0C6-44F6-B27F-522C5C3895A7) Time elapsed: 2 minutes, 28.000 seconds Backup canceled. Total time elapsed: 2 minutes, 31.000 seconds

In Console logs, I see:

17:01:34.124199 +0100 powerd Process backupd.624 TurnedOff BackgroundTask "Time Machine backup" age:00:16:03 id:47244673428 [System: PrevIdle DeclUser kDisp] 17:01:34.126417 +0100 powerd Process backupd.624 TurnedOff PreventUserIdleSystemSleep "Time Machine backup" age:00:16:03 id:4295000469 [System: PrevIdle DeclUser kDisp]

20:55:21.690979 +0100 backupd Claim 954EE5FE-C4AA-481E-8DE2-3B7462EEFDF5 was revoked

20:55:25.099189 +0100 backupd Failed to unmount disk mounted at '/Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/namehere/2017-1 1-13-202006/Macintosh HD', error: { Action = Unmount; Target = "file:///Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/namehere /2017-11-13-202006/Macintosh%20HD"; }

20:55:25.101240 +0100 backupd Failed to unmount snapshot: com.apple.TimeMachine.2017-11-13-202006 source: Macintosh HD

20:55:25.376956 +0100 powerd Process backupd.257 TurnedOff BackgroundTask "Time Machine backup" age:00:35:41 id:47244673059 [System: PrevIdle DeclUser kDisp] 20:55:25.378105 +0100 powerd Process backupd.257 TurnedOff PreventUserIdleSystemSleep "Time Machine backup" age:00:35:41 id:4295000100 [System: PrevIdle DeclUser kDisp]

20:55:42.788218 +0100 backupd Received claim 70B146B7-2002-4C35-B235-F23A6F07EAD7 20:55:42.789623 +0100 backupd Claim 70B146B7-2002-4C35-B235-F23A6F07EAD7 granted in server 20:55:42.789715 +0100 backupd Claim 70B146B7-2002-4C35-B235-F23A6F07EAD7 invoked in server

It seems that Time Machine fails to unmount a local snapshot?

I have tried running backup in safe mode, but with no results either. What could I do to complete a backup again?

MacBook Air, macOS High Sierra (10.13.1), null

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Answer:

Following some advice from Time Machine failing to complete backup - Ask Different, I have found a solution.


I have disabled Spotlight, which apparently was preventing Time Machine from unmounting the local snapshot. Once Spotlight was disabled, backup was complete within a few hours.

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Nov 14, 2017 12:46 AM in response to Kappy In response to Kappy

Hi Kappy,


Thank you for your answer. Do I understand correctly that my current solution is only to wait for Apple to figure out Time Machine working with APFS?


I am a bit confused, reading that

you can back up an APFS formatted drive using Time Machine, as well as restore files from a Time Machine backup to an APFS formatted drive

But on the other hand:

Luckily, installing macOS High Sierra won’t automatically convert Time Machine drives to APFS, but it’s possible to change the drive’s format to APFS from within Disk Utility or via the Terminal app

Should I try to change the format/somehow migrate my TM to APFS or just the opposite?

Nov 14, 2017 12:46 AM

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Nov 14, 2017 11:41 AM in response to 3yakuya In response to 3yakuya

I recommend that you NOT format drives using APFS. There is limited compatibility with HFS+ drives. If you do desire to use APFS then use it only on an SSD that is used for a startup drive. Here are two articles that may be of help: Troubleshooting Time Machine- stuck preparing backup, and the deep event scan and Why have my Time Machine backups stopped or become irregular?.

Nov 14, 2017 11:41 AM

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Question marked as Solved

Nov 14, 2017 1:02 PM in response to 3yakuya In response to 3yakuya

Following some advice from Time Machine failing to complete backup - Ask Different, I have found a solution.


I have disabled Spotlight, which apparently was preventing Time Machine from unmounting the local snapshot. Once Spotlight was disabled, backup was complete within a few hours.

Nov 14, 2017 1:02 PM

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Question: Time Machine failing to complete backup - Failed to unmount local snapshot?