Timemachine Back-up in MacOS 26 (Tahoe) does not work on Synology DS920+ NAS

[Precheck]

Please kindly follow the steps below to change settings on your Mac.

1. Open Terminal on macOS, and edit /etc/nsmb.conf with vi:

• • sudo vi /etc/nsmb.conf

1. Change the value of signing_required from no to yes:

• signing_required=yes
  • 

1. Press the Esc key, then type ZZ or :wq to save the changes and exit vi.
2. Reboot your Mac.

Once you have completed the steps above on your Mac, please continue with the steps below to check settings on both your NAS and Mac.

[On your Synology NAS]

1. Ensure that DSM is properly configured for Time Machine backups. Try creating a new shared folder and set it as the Time Machine backup folder, rather than using the original one.
2. Ensure your NAS has enough free space.
3. Make sure the following options are selected in Control Panel > File Services > SMB > Advanced Settings > General:

• Maximum SMB protocol: SMB3
  • Note: Time Machine backups require SMB3, so please change it back to SMB3 if it was modified.
  • Enable Opportunistic Locking
  • Enable SMB2 Lease
  • Enable SMB Durable Handles (Cross-protocol file locking will be disabled)

1. Confirm the following options are enabled or properly set in Control Panel > File Services > Advanced> Bonjour:

• • Enable Bonjour service discovery to locate Synology NAS
  • Enable Bonjour Time Machine broadcast via SMB
  • Set Time Machine Folders

It works!

The secret was to open the sparsbundle in disk utilities, where I found a longer name for the spartsbundle, where our Swedish characters were used. Exchange those characters to anything else in the span of a-z, hit return, and try two more TM-backups. The second one flies as the wind! Beautiful! Thanks all!

THANK YOU!! The real solution for me was to RENAME the APFS Drive! Thank you SuperMek_original!

I was struggling in the last two weeks to make it work. I tried everything including the solution marked as the famous. That DOES NOT worked for me! Only the renaming worked because my APFS disk name is had also contained special characters like () and áéöő. So I renamed it to TimeMachineHP with the disk manager and immediately started to work. Thank you!

The solution proposed by karel250 worked like a charm. I had the letter "ä" on the volume. An ordinary letter in Swedish but not in English. I changed it to the letter "a". Fixed my time mashine.

Thanks you karel250.

Yes, this worked (karel250)! In czech language system set the route in the .spuresbundle to "Záloha svazku ......" I rename this to "Zaloha svazku...." and TM worked.

Apple have to fix this problem. System automaticaly create route "Backuf of......." translated by language setting with diacritic. It make a problem.

Hi all,

I have been facing the same trouble during the backup - my disc was disconnected. I opened the disk utility as another user in this conversation and I found the backup image bundle name "Zálohy svazku ..." has in it's name the letter "á", so I renamed it to "Zalohy svazku ..." and now the time machine backup works.

Hi all,

I have been facing the same trouble during the backup - my disc was disconnected. I opened the disk utility as another user in this conversation and I found the backup image bundle name "Zálohy svazku ..." has in it's name the letter "á", so I renamed it to "Zalohy svazku ..." and now the time machine backup works.

I had the same issue. "Reservekopieën <computername>" is a name given by MacOS so I guess anyone using MacOS in Dutch (and most likely Flemish) will suffer from this issue. I solved it by translating "Reservekopieën" back to "Back-ups". Note that this only concerned the name of the disk when the sparse bundle is mounted.

This means that this would fail in the Netherlands at all times as it always starts with "Reservekopieën <computername>"?

In my case it did and I had to change the entire name. Thank you @karel250 for the fix!

Did this. Helped against my old Synology DS-414 (had a backup). The new Synology DS-923+ wasn't happy though. Found out I could change my computer name though and this looses all my Swedish characters. Time Machine running now and I'm waiting for success!

Check your netbios and wins name!

You could try deleting the destination in Time Machine settings, then re-adding it (select the option to claim the backups on the re-added drive).

I am experiencing the same issue. Based on the analysis so far, it appears to be a macOS 26 problem rather than an NAS issue. When the existing backup is deleted from the NAS, and a new storage is added followed by starting the backup, the network transmission increases to around 300 MB but then stops shortly afterward. At that point, folders and files are created normally on the NAS. If it had been a permissions issue, the connection would have failed from the beginning.

It seems that the problem occurs during the process of creating a Time Machine backup on macOS.

I hope this can be resolved soon.

Hello,

I have the same problem with a new clean installation of macOS Tahoe 26. I back up data not only to Synology but also to Truenas, using the SMB protocol in both cases. Backups do not work in either Synology or TrueNAS. The backup stops at the "Preparing" stage, regardless of whether encryption, username, or password is enabled. On my other laptop with macOS Sequoia 15.7, backing up using the SMB protocol works without any problems.

In my case, the issue was caused by Korean characters included in the Time Machine image. After changing the image description to use only English, the backup proceeded normally. Thank you. karel250

.

I have a Synology DS223j configured based on Synology's kbase article, and it's backing up my 16" M4 Pro MacBook Pro running macOS 26 just fine, and has been doing so since I installed Tahoe yesterday. Last backup completed a few minutes ago.

Have you tried restarting the NAS?