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

I am now on my second iMac in 3 months. The first one had the time machine issue out of the box- had to call the first day I had it. I spent hours and hours troubleshooting over a few weeks- on the phone with apple, different cords, new drives, reinstalled the OS, etc. That iMac became an insane nightmare to the extent that it was crashing every 5 minutes. I just got my replacement. Used a brand new drive to run a time machine backup, managed to make one and I'm right back to the error message about not making another backup-- error occurred while creating the backup folder. Ultimately, I was told it is some kind of bug in the OS and I just have to wait. I am so disappointed in Apple. This is such an important part of my data management as a professional photographer. This has been going on for months and they still have no fix. They need to stop rushing to get these OS upgrades out without testing them enough for issues. The upgrades have become more and more troublesome over the years.

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.

Thanks for your note. I don't know about the exact formatting, but until this last Monday I was running Mojave, upgraded from perhaps Sierra (??) before that. I'm running a Mid-2015 iMac and the external drive (MyBook for Mac) has backups back to 2016. What you note is basically where I'm at. I have a new external drive arriving Friday and had just planned to start over (so that I didn't eliminate a restore option by reformatting the old disk). What is giving me pause is that if there's some other glitch in the Big Sur installation and I get the same error with the new disk, then I'm out $180 for no reason. That's why I'm wondering if this "removing snapshots" recommendation is worth a try before tearing open a new disk. If I have to do a restore to Mojave and then re-install Big Sur to get TM functioning, I need that MyBook backup not to be corrupt (BTW, I can enter TM and see the backups as usual, just can't get it to make a new backup). Any thoughts will be most appreciated. Thanks.

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.

Thanks for all the help. I'm way out over my ski tips on this one. . .

I tried a backup and copied the log. It is quite long, so tried to paste below where it appears to start to go wrong. I've removed the name of my computer and replaced with XXXXXXX. Otherwise this is exactly as it appears. I'm going to try the other steps this weekend, but wondering if any of the following sheds light on the issue:

2021-09-09 21:37:04  Cached event database was unreachable at /Volumes/My Book for Mac/Backups.backupdb/XXXXXXX iMac (79)/2021-09-09-213658.inProgress/C309C9CB-6C9A-4A34-933E-01F603BB81A8/.87EB482A-B6F5-3F9A-9C2A-FD1E652BE9C9.eventdb

2021-09-09 21:37:04  Possible strategies for "Macintosh HD - Data" (device: /dev/disk2s1 mount: '/System/Volumes/Data' fsUUID: 87EB482A-B6F5-3F9A-9C2A-FD1E652BE9C9 eventDBUUID: E59C3A04-F682-4779-BB78-0AD01E37922B) (<EventMarker 2021-09-06 20:59:35 +0000 75743201 E59C3A04-F682-4779-BB78-0AD01E37922B 0>): first backup, deep scan, FSEvents,

2021-09-09 21:37:04  Using FSEvents for source: "Macintosh HD - Data" (device: /dev/disk2s1 mount: '/System/Volumes/Data' fsUUID: 87EB482A-B6F5-3F9A-9C2A-FD1E652BE9C9 eventDBUUID: E59C3A04-F682-4779-BB78-0AD01E37922B)

2021-09-09 21:37:04  Read 0 clone families from /Volumes/My Book for Mac/Backups.backupdb/XXXXXXX iMac (79)/2021-09-06-174437/.87EB482A-B6F5-3F9A-9C2A-FD1E652BE9C9.clonedb

2021-09-09 21:37:04  Buffering events...

2021-09-09 21:37:04  Unrecoverable zero fileid - path: 'Users/XXXXXXX/Library/Containers/com.apple.Safari/Data/Library/Caches/com.apple.Safari/WebKitCache/Version 16/Blobs/97829D2F9B149F4B0DBD93B1D000E22F51831C81', flags: 00100200

2021-09-09 21:37:04  Event collection stopped because of error: Error Domain=com.apple.backupd.ErrorDomain Code=303 "(null)"

2021-09-09 21:37:04  Failed to collect events for "Macintosh HD - Data" (device: /dev/disk2s1 mount: '/System/Volumes/Data' fsUUID: 87EB482A-B6F5-3F9A-9C2A-FD1E652BE9C9 eventDBUUID: E59C3A04-F682-4779-BB78-0AD01E37922B), error Error Domain=com.apple.backupd.ErrorDomain Code=303 "(null)" UserInfo={FailedStrategy=16}

2021-09-09 21:37:07  Unmounted local snapshot: com.apple.TimeMachine.2021-09-09-213702.local at path: /Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/XXXXXXX iMac (79)/2021-09-09-213702/Macintosh HD - Data source: Macintosh HD - Data

2021-09-09 21:37:07  Mountpoint '/Volumes/My Book for Mac' is still valid

2021-09-09 21:37:07  Mountpoint '/System/Volumes/Data' is still valid

2021-09-09 21:37:07  Backup failed (303: BACKUP_FAILED_PREFLIGHT_STAGE_GATHER_EVENTS)

Any thoughts are greatly appreciated.

Thanks.

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.

I am using Big Sur. Interestingly, cannot find a folder called Containers by searching through the file directory. When I use the Go to folder "~/Containers", I get the message: The folder can't be found. Could it be hidden, somehow? Don't know that I've ever used that command in Finder before, but I'm entering it exactly as noted above.

True, it is hidden by default. Just open Finder, While holding Option on the keyboard, click Go on the top menu and choose Library, (About half way through the menu). As long as you hold down Option, the Library will show.

So you can:

Quit Safari.

Save then delete ~/Containers/com.apple.safari.

Restart Mac, and launch Safari again to re-create the corrupted file, and try backing up again. Worth a try anyhow.

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.

great thanks - plenty of options there ;-)

will give them a try tomorrow

plenty of space on both drives (1tb free on backup & 2tb free on mac)

as I said above - problem has been solved

Good to hear! Thanks. 👍