OMV / timemachine - share name contains invalid characters?

1st Official Post

    New OMV 7.x install on raspberry pi 5. Configured a SMB share called tmback that I am able to access and see from Finder. When running timemachine backup it errors out with "Backup Failed", although it does connect and I see bundle files created on the OMV share. In the samba logs on the pi 5, I see a number of errors like this, I assume it is choking on the . (dots) here, cifs._smb._tcp.local./, but where did they come from??


    [2025/01/05 10:03:42.008895, 0] ../../source3/param/loadparm.c:3436(process_usershare_file)

    process_usershare_file: share name /cifs._smb._tcp.local./tmback contains invalid characters (any of %<>*?|/\+=;:",)


    On the time machine logs from the mac, I see a number of these errors as well:


    2025-01-05 10:16:35 Failed to read capabilities for '/Volumes/tmback', error: Operation not permitted

  • macom

    Approved the thread.
    • Official Post
    Quote from ljhardy

    [2025/01/05 10:03:42.008895, 0] ../../source3/param/loadparm.c:3436(process_usershare_file)

    process_usershare_file: share name /cifs._smb._tcp.local./tmback contains invalid characters (any of %<>*?|/\+=;:",)

    This looks like related to mDNS/Zeroconf. But other than that i have no idea where the problem comes from nor how to fix it.

    Does OMV support time machine backups to volumes formatted HFS+ or APFS? It seems to work if I format EXT4, but that's not recognized by Mac. I would like to do the initial backup with the disk directly attached to the Mac, and then subsequent backups to OMV. I tried the initial backup to OMV, but there is a lot of data and it was going to take 6 hours, it was interrupted mid-way by a network glitch. ( everything is ethernet attached )


    When I formatted the drive HFS+ or APFS and did the initial backup on the MAC, the file system isn't recognized by OMV.

    Yes, I understand that. But can you do the initial backup via time machine to the disk directly from the Mac, and then move that drive to OMV for subsequent backups? If yes, how does that drive need to be formatted to work with both Mac directly, and with OMV as a time machine target? It appears that OMV will not recognize the disk if it already contains the initial time machine backup, formatted either APFS or HFS+.

    • Official Post

    You have to use a Linux filesystem like EXT4, XFS, BTRFS. APFS is not supported on Linux afaik. HFS is supported, but you have to test that.

    If you want to use all features from OMV then the filesystem has to be POSIX compliant and support extended attributes.

    Quote from ljhardy

    Yes, I understand that. But can you do the initial backup via time machine to the disk directly from the Mac, and then move that drive to OMV for subsequent backups?

    Simply said: NO, not possible.

    Raspi 4B, 4GB RAM, SSD-Boot, 2TB & 1TB SSD as data-disks in Sata/USB enclosure, IcyBox USB3-Hub

    Like 1

    To clarify, Time Machine operates differently when backing up to a network share compared to local storage. In the former case it places everything in a sparsebundle disk image, but in the latter it uses regular files and folders, so moving a drive between those 2 'connections' simply would not work.


    The actual disk format of any network storage is transparent to the 'client'. So whether OMV storage uses ext4, XFS, etc makes no difference. TM is simply operating over SMB and knows nothing about the disk format used for that storage. However, that can affect how the files might be treated which is why TM uses a sparsebundle in those situations as that 'disk image' can be created as an APFS volume which TM knows how to deal with and make use of features it requires such as snapshots or hard linking directories, while being abstracted from the actual disk format of the storage and even the network protocol to a certain extent.


    TM's sparsebundle is a lot of relatively small files for which ext4 is ideally suited and seems to be the recommended format for TM storage on a network share.

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