[Samba] macOS monterey unable to back up to Samba 4.14.12

[Florian Fainelli]

Hi all,

I have been trying different configurations to get one of my macOS 
Monterey machine to back up to a samba4 installation on a Raspberry Pi 
4B using OpenWrt. Since this is an OpenWrt installation the package is 
heavily stripped to its minimum so here is the list of vfs modules being 
installed:

ls /usr/lib/samba/vfs/
cap.so            commit.so         default_quota.so  fake_perms.so 
fruit.so          offline.so        recycle.so        shell_snap.so 
virusfilter.so    worm.so
catia.so          crossrename.so    dirsort.so        fileid.so 
io_uring.so       readonly.so       shadow_copy2.so   streams_xattr.so 
widelinks.so      xattr_tdb.so

The error reported by the Mac client is that a sparsebundle file gets 
created but ultimately the backup preparation does not go through and 
shows "The backup disk image could not be created".

During the short time where the .sparsebundle folder is created and 
visible (it gets deleted upon failure), the permissions all look similar 
to those of the other working backup.

The Mac does complain about not being able to read a number of files 
under the .sparsebundle folder that I can create just fine using Finder 
or the OpenWrt device itself, so it sounds like as if the files were 
attempted to be created with attributes that are unsupported and we 
failed to read them back.

The same samba 4 installation works great on older Macs though. 
Underlying filesystem is ext4.

My relevant smb.conf section for that share is below:

[TimeMachine]
         path = /mnt/backup/TimeMachine
         create mask = 0666
         directory mask = 0777
         read only = no
         guest ok = yes
         guest only = yes
         fruit:encoding = native
         fruit:metadata = stream
         fruit:veto_appledouble = no
         fruit:nfs_aces = no
         fruit:posix_rename = yes
         fruit:wipe_intentionally_left_blank_rfork = yes
         inherit permissions = yes
         fruit:time machine = yes
         vfs objects = catia fruit streams_xattr  io_uring

Thanks for reading me!
-- 
Florian