Time Machine couldn’t complete the backup to “TimeMachine”. An error occurred while preparing the backup

Hey there! For this, I may, as I posted before, (Appears the OP’s cause was something different, due to the logs), I would:

Disconnect any external drive you use for Time Machine, (Eject first).

Turn OFF Automatic backups in System Preferences > Time Machine.

Open Terminal in Finder > Applications > Utilities.

Paste this command to clear the Time Machine snapshots, and press Return afterwards.

sudo tmutil thinlocalsnapshots / 999999999999999 4

Once it finishes, Restart, re-connect the external drive, re-enable Time Machine and test again.

PS: Before running the command, also delete the incomplete backup in Finder:

Double click the external drive on the Desktop, or in the Finder Sidebar.

Open “Backups.backup”, open the name of your Mac, scroll to the bottom, (Usually), and move the tile of the incomplete backup, “Usually says In Progress”. Then try the steps above.

Otherwise, how is your Mac and external drive’s storage? Hope that helps!

Hi there!

I’ve come across this multiple times and read the replies to you and the OP.

It sounds like, to me, especially if you can’t backup to any external drive, even after reformatting properly, it may be an OS/content issue as you stated.

First:

Are there any connected drives to your Mac(s) that are also set to be backed up? Of course if so, eject, disconnect and try again.

Your suggestion of excluding files or directories from being backed up is also right on, there is one setting to allow/remove by default, which makes it easier, is I believe System files and Apps, that’s a good test. You can add that to be excluded from Time Machine Advanced Preferences, restart and test.

I know you’ve also probably run first aid, etc. which is another good step if all else fails. Otherwise:

IF the first backup completes okay, but the subsequent ones don’t, then I’d try clearing the Time Machine snapshots, restarting and trying again.

You can do this by opening Terminal from Finder > Applications > Utilities. Then run and enter the following command:

sudo tmutil thinlocalsnapshots / 999999999999999 4

(Yes, that’s 15 9’s)

Restart your Mac and try again.

Otherwise, if all else fails, I may delete the Time Machine plist/restart:

Open Finder > Go > Computer > Macintosh HD (Usually) > Preferences.

Save a copy them delete com.apple.timemachine.plist, then delete the file from that location, restart and test again. If you do this, you will have to choose your backup disks again, however if it is an issue with this property list, it may just fix the problem.

You can also use Terminal to check the Time Machine status, it’s not much, but you can run and enter:

tmutil status

And of course, testing the backup process while in Safe Mode or in another active user account is a good test/solution.

Knowing, of course if another Mac has the same issue with the same external drive, or the same Mac has an issue with another external drive would be revealing. Hope something here helps!

I had similar problems that I could not pinpoint - my problem was due to a corrupted file which was stopping the backup

this worked for me

Get the Time machine logs

https://discussions.apple.com/thread/250226175

look through them and see if you can see a file name or some other error that is causing it

here is my last post in the thread that helped me the most

https://discussions.apple.com/thread/253012759?answerId=255778958022

SOLVED !

ok I removed the snapshots & restarted

still didn't work

tried to find "com.apple.timemachine.plist" but it simply isn't there - maybe BigSur does it a different way

anyhow I sourced the log file again and found the following mention of a file named

"Iggy & The Stooges/1-01 Search and Destroy.mp3"

that file was added from a download around the same time as the problem started

I imagine Iggy Pop corrupting something ... unthinkable !!

anyhow I removed the file and all seems to be working fine now

here is the error showing in the logs

2021-08-24 07:21:57 Failed to copy '/Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/iMac/2021-08-24-071250/Macintosh HD - Data/Users/user/Music/iTunes/iTunes Music/Iggy & The Stooges'to '/Volumes/mac backup/2021-08-24-071251.inprogress/Macintosh HD - Data/Users/user/Music/iTunes/iTunes Music', error: -48, srcErr: NO

2021-08-24 07:21:57 Failed to copy '/Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/iMac/2021-08-24-071250/Macintosh HD - Data/Users/user/Music/iTunes/iTunes Music/Iggy & The Stooges/1973 - Iggy & The Stooges/1-01 Search and Destroy.mp3'to '(null)', error: -8062, srcErr: NO

2021-08-24 07:21:57 Failed copy from volume "Macintosh HD - Data"

I had the same problem early today. Open the time machine preferences, select disk, remove the disk you are using, then if you are on AirPort, make sure the name on the drive you are using is not duplicated on finder locations. if you are using an external make sure the name is not duplicated in finder locations. After that, on backup disk click on the one you want to designate and use that disk. this worked for me without loosing my prior backups.

I hope this help!

Nothing to do with Mac OS. After researching what could be causing the error, I excluded (check your time machine settings, options...) the OneDrive folder from backups... It works like a charm and now time machine resumed with its hourly routine.

[Edited by Moderator]

SOLVED !

ok I removed the snapshots & restarted

still didn't work

tried to find "com.apple.timemachine.plist" but it simply isn't there - maybe BigSur does it a different way

anyhow I sourced the log file again and found the following mention of a file named

"Iggy & The Stooges/1-01 Search and Destroy.mp3"

that file was added from a download around the same time as the problem started

I imagine Iggy Pop corrupting something ... unthinkable !!

anyhow I removed the file and all seems to be working fine now

here is the error showing in the logs

2021-08-24 07:21:57 Failed to copy '/Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/iMac/2021-08-24-071250/Macintosh HD - Data/Users/user/Music/iTunes/iTunes Music/Iggy & The Stooges'to '/Volumes/mac backup/2021-08-24-071251.inprogress/Macintosh HD - Data/Users/user/Music/iTunes/iTunes Music', error: -48, srcErr: NO

2021-08-24 07:21:57 Failed to copy '/Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/iMac/2021-08-24-071250/Macintosh HD - Data/Users/user/Music/iTunes/iTunes Music/Iggy & The Stooges/1973 - Iggy & The Stooges/1-01 Search and Destroy.mp3'to '(null)', error: -8062, srcErr: NO

2021-08-24 07:21:57 Failed copy from volume "Macintosh HD - Data"

How is your TM drive formatted? We know that if starting from scratch with Big Sur Time Machine will format the drive APFS. If your drive is formatted OS X Extended (journaled), rather than get a new drive reformat the drive to APFS and see if that will work.

However, if you have files that you need on the TM drive that are not on you working boot drive you may not want to go that route.

How much free space do you have on your boot drive? If there's not enough for a new local snapshot Time Machine won't backup.

You certainly can try removing the local snapshots and then see if TM will work. TM will just create new local snapshots as it goes along.

Just a note on new drives. If you keep that drive reformat it to APFS w/GUID partition before using it and do not use any software that may come with it. The OS does not need it to manage external drives.

If you’re 100% sure the drives (with right format and potential repair in dusk utility to be double sure), cables and USB ports are fine, here’s what the complete amateur I am would suggest:

• Check that the folders you want to backup can’t create conflicts and exclude others from the backup options (linked files, cloud-based backup drives like OneDrive, Box or Google Drive)
• Restore your OS and latest backup
• Consider upgrading to a more recent version of OS (if your machine can take it)

I used terminal

this code give you the logs

printf '\e[3J' && log show --predicate 'subsystem == "com.apple.TimeMachine"' --info --last 6h | grep -F 'eMac' | grep -Fv 'etat' | awk -F']' '{print substr($0,1,19), $NF}'

copy & paste the log info somewhere

then "exit" terminal

Hey there!

Everyone’s backup issue could be from a different cause. Although you are hesitant to remove the local snapshots, due to the same issue happening on two separate external drives......just know that the snapshots are stored locally on your Mac, NOT on your external drives, so this would be a valid step for you to try, likewise considering the logs you sent. Hope it works out for you as well.

Someone else maybe able to shed more light on the Safari Container reference though. Although thinning the snapshots is a fairly simple possible solution unless you didn’t mind delving deeper into the troubleshooting abyss. 😁.

I'm clutching at straws a bit here but this line seem to be the issue as it appears just before everything stops

2021-09-10 17:55:00 Unrecoverable zero fileid - path: 'Users/XXXXXXX/Library/Containers/com.apple.Safari/Data/Library/Caches/com.apple.Safari/WebKitCache/Version 16/Blobs/97829D2F9B149F4B0DBD93B1D000E22F51831C81', flags: 00100200

I looked in my system and could not find a "containers" folder in my system library - but you may be using a different version of the OS (I'm using big sur)

Have a look and maybe you can temporarily change the name of that folder or file and see if the error message changes -

or

in Timemachine Preferences > Options - add one of the directories in that error listed above and see if it work then

also

maybe clear your safari cache ??

https://clear-my-cache.com/en/apple-mac-os/safari.html

To get to the Containers folder:

Open Finder > Go > Go To Folder and enter:

~/Containers

Then press Go or hit Return

Not sure if modifying/deleting the file in that path would fix the problem, but worth a shot I suppose, I would just save the file, delete original and restart if doing so.