Hello,

I am busy testing Unraid, so far I really like the software however I am unable to get Time Machine to work.

I have 4x 4TB HDD's running in a raidz1 pool. I am running Unraid 7.2 andI create the SMB share as follows:

• minimum space: 1 KB

• primary storage: name of the zfs raidz1 pool

• secondary storage: None

• export: Yes / Time Machine

• time machine volume size limit: 2048000 MB

• case-sensitive names: Auto

• security: Private

• relevant user has read/write access

I am able to mount the share as a Time Machine volume on my Mac (Sonoma 14.3). I specify to encrypt the backup and set a disk usage limit of 2.0 TB (also tried 1.9 TB to be sure it was less than time machine volume size limit).

When it comes time to backup I get the error that the backup disk image could not be created. Specific text of the error: "The backup disk image could not be created".

I have tried many times, restarted both machines and tried re-creating / re-adding the share. Where am I going wrong?

It shouldn't need anything special because of being on zfs, see if this helps:

I'm having the exact same problems, with a new (trial) install of unraid 7.2.0 with a freshly created 4x8tb ZFS raidz1 pool with no compression or encryption.

I've tried a bunch of different smb options, even going to far as even trying leaving the share public.

For the smb share, it's exported as Yes/Time Machine, size limit of 2000000MB (2tb), case sensitivity auto, and security i've tried everything, it's currently public.

For the SMB global settings, hide dot is off, multichannel is off, enhanced mac interoperability is on, and netbios is off.

Mac is a M1 macbook pro running Tahoe 26.1, using encrypted backups on the mac side.

What's interesting is that it's clear that the mac is definitely mounting and writing to the smb share, as a terminal on the unraid server shows the creation of:

Creates a directory in the share named: mymac\ 2025-11-17-154930.incomplete/

with files:

drwxrwxrwx 4 jeff    users    8 Nov 17 15:49 ./
drwxrwxrwx 3 nobody  users    4 Nov 17 15:49 ../
-rwxrw-rw- 1 jeff    users  575 Nov 17 15:49 Info.bckup*
-rwxrw-rw- 1 jeff    users  575 Nov 17 15:49 Info.plist*
drwxrwxrwx 2 jeff    users    7 Nov 17 15:52 bands/
-rwxrw-rw- 1 jeff    users    0 Nov 17 15:49 lock*
drwxrwxrwx 2 jeff    users    7 Nov 17 15:52 mapped/
-rwxrw-rw- 1 jeff    users 1092 Nov 17 15:49 token*

and when it fails a couple of minutes later with the error:

"The backup disk image could not be created."

Once Time Machine fails, it leaves these files in the share;

drwxrwxrwx 2 jeff   users    5 Nov 17 15:52 ./
drwxrwxrwx 3 nobody users    4 Nov 17 15:52 ../
-rwxrw-rw- 1 jeff   users  575 Nov 17 15:49 Info.plist*
-rwxrw-rw- 1 jeff   users    0 Nov 17 15:52 com.apple.TimeMachine.sync.6DB6F447-3C43-4456-A130-5016634CAD83*
-rwxrw-rw- 1 jeff   users 1092 Nov 17 15:49 token*

The same macbook is backing up to a synology nas just fine. I've tried rebooting everything multiple times.

I'm completely stuck at this point, any suggestions? It sounds identical to the OP's issue.

I’m running into the same issues after upgrading to 7.2.0.
My old Time Machine backup started throwing an error saying it ran out of space. I went ahead and set up a new one, but even with a fresh backup I’m now getting the message that "the backup disk image could not be created."

Have any of you recently upgraded the macOS version, or is it still the same one that worked before?

I’m on MacOS Tahoe 26.1 (25B78).

After digging into this a bit more, it really does look like the issue comes from Tahoe. It seems like SMB3 is misconfigured on the Mac side, which is what’s causing the failures. There are plenty of threads out there showing this happening across different NAS platforms that use SMB for Time Machine. I tried a few of the fixes suggested on the Synology forum, but none of them worked for me. If anyone wants to check it out, here’s the link: https://community.synology.com/enu/forum/1/post/194563

I'm running MacOS Sonoma 14.3 (23D56).

A few weeks ago I was testing Unraid with my 4x HDDs in xfs in an array. I had no issues with the SMB Time Machine then.

The problem has appeared since switching the setup to a zfs pool or possibly due to upgrading from Unraid 7.1.4 to 7.2. Looking at the release notes for 7.2 it does mention changes to the SMB config:

In smb.conf, set smb3 directory leases = no to avoid issues with the current release of Samba

I might try to revert this and see if it helps.

10 hours ago, timeisweird said:

I might try to revert this and see if it helps.

That option didn't exist before, so it was also disabled in previous releases, and having it enabled may cause more harm than good; still, it may be worth a try.

12 hours ago, JorgeB said:

That option didn't exist before, so it was also disabled in previous releases, and having it enabled may cause more harm than good; still, it may be worth a try.

I commented out "smb3 directory leases = no" and made it persistent with a copy command in the /boot/config/go file. Unfortunately it does not solve the Time Machine error.

For what it's worth I also tried without using Time Machine encryption and that also made no difference.

Seeing as I'm still testing Unraid and don't have any important data on my pool, I'm tempted to try with the drives configured in an array again but on 7.2.1. Although I really wanted to make use of zfs.

Edited November 21, 2025Nov 21 by timeisweird

I would try creating a new share first, and make sure you follow this:

https://docs.unraid.net/unraid-os/using-unraid-to/manage-storage/apple-time-machine/

There's a Samba bug that may affect TM with 7.2.x. There was a patch going into Samba 4.23.3, but Unraid uses 4.23.2. Also, the bug has been reopened with an additional patch, and that hasn't been merged yet, so it may be worth retesting with 7.1.4

https://bugzilla.samba.org/show_bug.cgi?id=15926

I'm new to unraid (half-way into my trial), and running Tahoe 26.1.

I can backup with time machine just fine to Synology, and just figured out that I can backup to the timemachine-in-docker container on unraid hack as well, so it appears that the mac is ok.

That seems to point to something wrong with the config of smb on unraid to me...

1 hour ago, jeffbeadles said:

That seems to point to something wrong with the config of smb on unraid to me...

See the post above, there's a Samba bug that breaks TM for some users.

On 11/22/2025 at 3:11 PM, JorgeB said:

There's a Samba bug that may affect TM with 7.2.x. There was a patch going into Samba 4.23.3, but Unraid uses 4.23.2.

I am also affected by this bug on macOS Tahoe 26.1 with Unraid 7.2.2.

@limetech Is there a way to manually upgrade Samba to the 4.23.3 version in Unraid, so that the issue is resolved, or must we wait for a upcoming release?

I am also experiencing the same issue. Also macOS 26.1 with Unraid 7.2.2

11 hours ago, greenflash24 said:

Is there a way to manually upgrade Samba to the 4.23.3

Not that I know of, but note that the release does not resolve all the issues; there's still an additional patch that hasn't been merged yet. If you need TM better to remain on 7.1.4 for now.

@JorgeB Do we need to submit a ticket to Limetech so this can be patched?

54 minutes ago, timeisweird said:

Do we need to submit a ticket to Limetech so this can be patched?

You will need to wait for Samba to release a new version with the latest fix included, then the next Unraid release after that should include the fix. For now, if you need TM, best to use 7.1.4

Samba 4.23.4 was released on December 12, 2025. This patch release should include the final fix for the TimeMachine issues.

Now we need an update procedure for upgrading Samba in Unraid 7.2.2 or we need to wait for a version upgrade from @limetech .

52 minutes ago, greenflash24 said:

or we need to wait for a version upgrade

This, the next Unraid release should include the Samba update.

Unraid 7.2.3 with Samba 4.23.4 has been released, but unfortunately I seem to have the same "The backup disk image could not be created." error.

Edited December 19, 2025Dec 19 by 8GDWLbk9HRKtlJJvaiFG

14 minutes ago, 8GDWLbk9HRKtlJJvaiFG said:

Unraid 7.2.3 with Samba 4.23.4 has been released, but unfortunately I seem to have the same "The backup disk image could not be created." error.

I can’t say for sure if this will fix your issue but over the years it has fixed mine multiple times. Have you tried a full Recovery install of macOS?

2 hours ago, wgstarks said:

I can’t say for sure if this will fix your issue but over the years it has fixed mine multiple times. Have you tried a full Recovery install of macOS?

Tried that and it does not work. Still broken with new unraid release.

...

https://forums.unraid.net/topic/178033-bmartino1-user-scripts/#findComment-1478661

smb extra... make your own time machine share...

#example Apple Time Machine (let apple define quota not unraid...)
[TimeMachine]
    path = /mnt/user/TimeMachine
    browseable = yes
    read only = no
    guest ok = no
    # time machien requires a samba user connected!
    valid users = samba_user root
    writeable = yes
    acl map full control = yes
    acl allow execute always = yes
    map archive = yes
    map system  = yes
    map hidden  = yes
    create mask        = 0660
    force create mode  = 0669
    directory mask     = 0770
    force directory mode = 0770
    force user  = root
    force group = root
    vfs objects = catia fruit streams_xattr
    fruit:encoding = native
    # If you want Unraid to advertise this as a Time Machine target:
    fruit:time machine = yes
    # If you want unraid asigned size quota
    ; fruit:time machine max size = 0
    fruit:metadata = stream
    fruit:resource = stream
    fruit:locking = none
    # ACL + extended attributes
    ea support = yes
    store dos attributes = yes

you must have a smaba user made inthe urnaid web ui and set valid users... then connect to TimeMachine as that users.. then one can use apple time machine on apple sied to set quota and connction via settings...

Please try creating a new TM share to start a new backup.