Time Machine backup on macOS Sequoia cannot be completed

I couldn’t make the Time Machine work with 15.0 or 15.0.1, so I used Terminal to add the code snipped from keithfromsalado: "sudo rm -f /etc/nsmb.conf” and restarted the Time Machine set up. It worked perfectly. Thank you, keithfromsalado!!

From completely formatting my previous backup drive did not solve the Time Machine failure to back for me.

I given up. I purchased a 3rd party option for backups. Not the same as TM, yet better than not having anything!

I tried the terminal command stated by keithfromsalado: "sudo rm -f /etc/nsmb.conf” and restarted my Mac. I tried Time Machine again and it worked! This command line completely resolved my Time Machine issue. Thank you, keithfromsalado!!

Unfortunately the terminal command didn't work for me. I've tried turning off Firewall as was implied. I have Removed the drives within the TimeMachine setting and re-added, I have run Disk FirstAid on both. I also run Netgear's Armor and though perhaps the TimeMachine protection within that app was the problem, but turning off hasn't resolved. I guess my next step is to start from scratch with my two APFS disks but that defeats the purpose of having a back up that I can go back months and even years to recover something I don't currently know I might be missing.

I was hoping that a fix would be available to us in the MacOS 18.1 release. Sadly, no. The failure of Time Machine backup to complete still is happening after upgrading my MBP M1. I've changed the frequency to Manual and am now requesting a backup when active on the MBP. Only then does it complete successfully.

Time Machine IMHO is VERY basic backup system! Throughout its history every Mac new Mac OS updates it will Startup a new backup each every time! You better off with your choice of shareware backups that continue though at least two backups until a new version come out and pick up where it left off before the upgrade!

Similar issue here, Time Machine Backup fails after 15.0 update. My TM drive is inside a 2012 Mac Mini (Catalina) on my network. It has worked pretty much without issue for many years until now. Error message is "Time Machine couldn’t complete the backup to XXX" and then "The backup disk image was ejected or disconnected from your Mac while backing up." Of course the drive was not ejected or removed as it is internal to the Mini. I tried the Terminal command fix and it did not work. Time Machine attempts to make the backup, finds the changes, starts copying files and then displays "11.7% done - Calculating time remaining, Zero KB copied." Then that fails and the error message is generated.

My wife's Macbook Air which is on Sonoma not Sequoia, still makes backups to the same Mac Mini, to the same internal drive (different partition) without any problems. So this is without question a Sequoia problem.

Been thinking about getting a new M4 Mac Mini to replace the 2012. I use it for all sorts of home server tasks including hosting Time Machine drives. I hope Apple gets the bugs out of Sequoia soon.

I found a solution for us for the same problem:

we have 2x users installed on our iMac: both with admin rights.

After each OS version update, TM was unable to complete the backup for the respective registered user.

Switching to the other user and restarting the backup there --> everything was OK.

Back to the first user --> then no more problem, the backup runs through.

So the problem obviously seems to have been a rights problem.

All backups are also made twice on different storage devices:

1x on an Unraid server (NAS) as an smb-share

1x to an external drive connected directly to the iMac (AFPS)

Initially, the backup didn't work for either of them. After the switch, the backup worked again for both of them.

So in this case it has nothing to do with the type of connection.

Hope it helps ...

I have the same problem, I removed the WDMyCloud drive from the Time Machine prefs, but, when re-adding it, the "Checking Capabilities of Time Machine backup drive" just hangs forever. Is there any other option?

I can mount and access the backup drive.

thanks.

I have the same problem. After removing the WD MyCloud Time machine drive, then re-adding it, I also got "checking capabilities of drive..." . Wouldn't add it. It would hang forever. Then I tried connecting with a different MyCloud server. It worked this time. .Was able to re-add the disk to TM.

thanks.

As I posted earlier, I was unable to successfully make a TM backup session after installing Sequoia. Today however, I was able to successfully back up after turning off the firewall on my MacBook. I then updated to 15.1 and successfully backed up with the firewall turned on. Can’t really explain this, but Time Machine now works properly.

I was seeing 'Back up Fail' and then I realised that after upgrading to Sequoia Time Machine had decided to remember an old TM disk which it couldn't find because I'd got rid of it - literally thrown it in the bin. The previous system software sensibly just worked with the disk that was actually connected and didn't try and find the old broken one. But Sequoia decided to make it complicated. So it turns out that backups were working fine but the message I was getting was that they'd failed. Once I deleted the old disk from TM settings it was fine.

That's a helpful observation and a reminder that similar symptoms may result from multiple causes. For those of us backing up to a NAS that is otherwise working fine, but failing to complete the backup we will need to seek further.

My suggestion is reformat the drive for Sequoias file system APFS because HFS+ is no longer supported by macOS 15

what does sudo rm -f /etc/nsmb.conf really do

How to disable SMB 1 or NetBIOS in macOS

How to disable SMB 1 or NetBIOS in macOS - Apple Support (CA)