Time Machine snapshot could not be created for the disk "%@"

Ok, I resolved the issue, and Time Machine is now backing up correctly.

To recap: This computer never had Catalina on it. Went straight from Mojave -> Big Sur. After upgrade to Big Sur, no Time Machine backups would work at all (to external USB hard drive or to a network store). They all failed with a message like "Time Machine could not back up the disk "%@" because a snapshot of the disk could not be created."

On the misbehaving machine, I had to remove the /Volumes/com.apple.TimeMachine.localsnapshots directory. This is a hidden directory, but you can delete it via the terminal if you have sudo or root permissions. I noted that in this directory were some snapshots from *before* Big Sur was installed.

sudo rm -r /Volumes/com.apple.TimeMachine.localsnapshots

Once that was deleted, I also deleted all the local snapshots using this terminal command (note that this listed and deleted snapshots from *after* Big Sur was installed:

sudo tmutil deletelocalsnapshots /

As soon as I did both of the above, Time Machine started working correctly.

I think the "%@" is a bug. It's used in the programming languages that Apple uses (Swift and Objective C) to say "put this variable in this string. I think they just forgot to put the disk name there.

If you look at the Console app right after this happens do you see any error messages that might help?

Found a new fix - without having to wipe your existing computer ;-)

You need to wipe out the external backup drive using APFS. If you want to use the external drive to backup multiple computers, you need to create individual volumes for each backup on the external drive.

Now the issue is Airport Time Capsules. Looking for a way to format the TC to APFS. I tried a factory wipe, but that didn't help.

Hey TJMatson - what happens when you run this command in a terminal?

sudo tmutil deletelocalsnapshots /

Any error messages from that? If it runs successfully, then try rebooting the computer to get it to actually free up the space. If that does not work, go into TimeMachine preferences and turn off automatic backups, then wait about an hour to see if your free disk space increases.

Ultimately, though, you may need to move some data off your drive to free up enough space for both TimeMachine to do its thing and for the upgrade from Catalina to Big Sur.

I'm running into the exact same issue, trying to backup a machine which was upgraded directly from Mojave to Big Sur (skipped Catalina) to a Synology Disk Station. Other Big Sur macs which were upgraded from Catalina have no problem backing up to the same destination.

I'm betting the problem is related to permissions on the local snapshot directory.

Hi,

Thank you very much for your long and fast reply. It's very appreciated!

Something very strange happened from my side. The day after, without doing anything, time machine error disappeared and started working like a charm...

Can't explain what happened but so far so good.

Just to let you know, my time machine device is a 2TB Western Digital USB disk connected via USB to an old AirPort Extreme station and I am running a Late 2018 MBP.

Hope you will enjoy you newly installed Mac OS.

Cheers,

Nicolas

I'm having this same issue when trying to backup to one of my Time Capsules. Always worked fine in Mojave, just upgraded to Big Sur yesterday. I tried erasing the disk, no change. Any other suggestions?

Mid 2015 MacBook Pro 15". I'm having the same issue, same error message after Big Sur upgrade. Time Machine was working fine before upgrade. Disk Utility First Aid says external drive if fine. Just to be sure I erased and reformatted it. Tried a variety of APFS formats, all failed. Oddly enough my 2018 MacBook Pro was also updated to Big Sur and Time Machine is working as expected. Working with Apple Support escalation team to get an answer. Right now they are moving it so some higher level engineers. I've given them a link to this forum topic. I'll report back if I learn anything.

Somebody get @KimballLarsen a medal! I've been living with this for a month just waiting for a smartypants to find a fix. Running those two terminal commands fixed the issue immediately. This should be posted more places. Seems like it's a common issue with the Big Sur update.

The terminal commands I posted above to remove the old TM backups from prior versions of the OS should have done the trick. If not, then the complete disk erase and clean install described by @KoolKiwi *will* definitely fix the problem (though it's quite a bit more work to do).

Did you get any error messages when you tried the solutions posted above?

Yea, the terminal codes didn't work. Received no errors when during the terminal command, so I was hoping that would have done the fix.

I haven't gone through the steps of performing a backup and system wipe of my laptop. Just can't do that during the week.