Mac & macOS

Instructions: Use Time Machine on the FritzBox

Using Time Machine with the FritzBox-NAS is not a problem, but requires a little preparatory work.

It doesn't always have to be expensive NAS be: Who a Fritz box from AVM can also use the router as a Time Machine drive with a little tinkering. The advantage: You don't need any additional hardware apart from a USB hard drive. The solution can be set up in just a few simple steps.

1a. Prepare external hard drive for Time Machine

First you need an external USB hard drive. This should have at least the capacity that your Mac has. For Macs with smaller data storage devices, an SSD may also do the trick, but conventional hard drives are cheaper. Then you have to prepare the hard drive for Time Machine use:

You must first format the hard drive in MS-DOS format.
You must first format the hard drive in MS-DOS format.
  1. Connect the hard drive to your Mac.
  2. Opens Disk Utility from the Utilities folder.
  3. Select the hard drive and click Erase. Attention: MacOS no longer shows the disk by default, but only the volume, which can lead to problems. Here you can read how to solve them.
  4. Give the volume a name, select "Format: MS-DOS" and "Scheme: Master Boot Record". Unfortunately Fritze can't do anything with other settings. Then click on "Delete".
  5. Click Done to confirm. After that, quit Disk Utility but leave the hard drive on the Mac.

1b. Create a Time Machine disk image on the hard drive

Now you need to create a disk image on the hard drive that is suitable for Time Machine backups. The Time Machine backups are later stored in this so-called growing sparse bundle. This makes the backup program independent of the file system on the Time Machine volume's base drive. This technology is also used in NAS devices.

With the right sparse bundle you create the actual Time Machine volume for the Fritz NAS.
With the right sparse bundle you create the actual Time Machine volume for the Fritz NAS.
  1. Open Disk Utility again.
  2. Click on "File -> New Image -> Blank Image" in the menu bar.
  3. Select the following settings here: "Format: MacOS Extended (journaled)", "Partitions: Simple partition - Apple partition table", "Image format: growing bundle image". The rest is secondary.
  4. You should set something unique as the name and file name, and the just formatted hard drive as the storage location.
  5. The size jumps to 100 MB with "Bundle image that grows with you" - change this setting to a realistic value, about "1 TB" or something similar, just what the hard drive has to offer. Then click on "Save".
  6. The sparse bundle is now created. You can click Done and exit Disk Utility.

2. Set up FritzNAS on the FritzBox

You can now disconnect the hard drive from the Mac and connect it to the USB port of your FritzBox (ideally the USB 3.0 port!). Now you have to make a few small settings on the FritzBox. To do this, first open the FritzBox admin interface in the browser You can then go to Home Network -> FritzNAS to see if the checkmark is “Storage (NAS) active“ is set and the hard disk has been recognized. Checks the hard drive if it hasn't already done so is the default. The hard drive is now made available in the network by the FritzNAS system. That's it for the preparations - now it's time for the actual Time Machine integration.

Now checks whether the FritzNAS is active and the hard drive has been integrated.
Now checks whether the FritzNAS is active and the hard drive has been integrated.

3. Set up Time Machine with FritzBox

To be on the safe side, first remove all existing Time Machine drives from Time Machine. Then open a Finder window and press (cmd)+(K) to connect to a server. Give as a server smb://fritz-nas a. Then click on "Connect". Now the Finder should show your NAS contents.

You must first mount the Fritz NAS.
You must first mount the Fritz NAS.

Now select the hard disk in the file overview and then the sparse bundle. Double click it. This will mount it in Finder.

Then you double-click on the sparse bundle, which is then mounted.
Then you double-click on the sparse bundle, which is then mounted.

Now open a terminal window from /Applications/Utilities/ and enter the following command there: sudo tmutil setdestination /Volumes/(VOLUMENAME). You have to replace "(VOLUMENAME)" with the name of the sparse bundle volume, in our case "TMSPARSE". So our command is: sudo tmutil setdestination /Volumes/TMSPARSE. Confirm with your Mac administrator password.

With a terminal command you set the bundle as a backup target.
With a terminal command you set the bundle as a backup target.

The hard drive on the FritzBox is now specified as a Time Machine volume. All other backup volumes will be thrown out - you can add them back later. Time Machine should now create the first backup on the FritzBox.

That's it: Time Machine creates the backup on the FritzBox.
That's it: Time Machine creates the backup on the FritzBox.

Attention, craft solution!

Unfortunately, this solution is a real handicraft solution. This means that we cannot guarantee that the backups will work afterwards, nor that they will actually happen regularly! If you want to be on the safe side, you shouldn't use a pure network solution as the exclusive backup solution for Time Machine anyway. Although some NAS systems dominate as the devices by Synology and Western Digital TimeMachine. However, it is better to always run a USB hard drive as well. That's not a problem, because Time Machine allows mounting multiple drives.

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Product prices and availability are correct as of the date/time shown and are subject to change. All pricing and availability information on at the time of purchase applies to the purchase of this product.
Product prices and availability are correct as of the date/time shown and are subject to change. All pricing and availability information on at the time of purchase applies to the purchase of this product.
Product prices and availability are correct as of the date/time shown and are subject to change. All pricing and availability information on at the time of purchase applies to the purchase of this product.

Christian Rentrop

Graduate journalist, born in 1979. First attempts at walking in 1986 at the Schneider CPC. In 1997 it went online. Ever since then as a scribbler in deadwood forests and on digital highways. Often also on the Vespa or with the caravan on the way. Daughter father since 2020, so always very happy about one small coffee donation.


  1. Had problems too.
    After finally mounting the file, I had an "unnamed" drive. I then had to rename this to TMSPARSE. Then sudo tmutil setdestination /Volumes/TMSPARSE and after that Time Machine was set up directly.

    Maybe the one person just needs to rename the Lw.

    Thanks for the instructions, otherwise I wanted to sell the last mechanical hard drive because it wasn't a sensible use.

  2. Hello Christian Rentrop,
    excellent description. Almost everything worked - except for the last action.
    I can see the drive on the Fritzbox via Terminal and "df -h". Unfortunately, I can't see it in TimeMachine.
    Is there another tip for this?
    Otherwise, as I said, a great description.
    Best regards,
    Thomas Itterman

  3. Hallo,

    thank you very much for your helpful article. I have 2 questions about this:

    Can you remove the USB disk from the fritzbox at any time and run the Timemachine directly on the Mac (e.g. take the disk with you on vacation)
    Can the disk be portioned, for example to have media storage in addition to the Timemachine, and consequently to classify both the Timemachine and the media access via the router?

    BG M

  4. Hi, I mounted the sparsebundle and the hard drive shows up in the finder, but in the time machine settings the hard drive doesn't show up. What can be the reason?

  5. Hallo,

    I find the quality and the wealth of detail in the instructions extremely positive. I have just one problem that I can't solve. I have a 12TB hard drive (WD My Book 25ED Media) and am failing to format it to "Format: MS-DOS" and "Scheme: Master Boot Record". Disk Utility on my MacBook Air M1 with Ventura 13.2.1 doesn't let me do this successfully. There is always the following error message: The storage medium is too large to be supported by the specified partition scheme. : (-69659).

    That's to be expected, since in my opinion the limit for this format is 32 GB. (like that "MS-DOS (FAT): Select this option if the hard disk is 32 GB or less."

    I am all the more surprised that a Toshiba hard drive with 2 TB was formatted so successfully here in the tutorial!?

    I would be very happy about a short hint, because I have not found a solution despite an intensive search.

    Thank you very much

  6. Hallo,

    I'm just despairing. The instructions are really good and easy to follow. However, I get the following message: "tmutil: setdestination requires Full Disk Access privileges.
    To allow this operation, select Full Disk Access in the Privacy
    tab of the Security & Privacy preference pane, and add Terminal
    to the list of applications which are allowed Full Disk Access.”

    In the settings for full hard disk access, I cannot authorize the sparse bundle separately.

    Can someone support me? The problem is probably between the keyboard and the chair =D

    I use a FRITZ!Box 6591 Cable (lgi) with Fritz!OS:7.29
    and macOS Catalina (10.15.5)

    Thank you!

    1. Hello, you simply have to go to System Settings, then to Security and Privacy, then to Full Disk Access, you have to add the Terminal App and then you only have to confirm sudo tmutil setdestination /Volumes/(VOLUMENAME) with Macbook PW and your hard disk should be recognized immediately

  7. unfortunately i only came across your site now and thank goodness in time at the age of 81. I'm currently in the process of replacing the vodafone cable router with one from avm, but I have to wait until it's finally available again. meanwhile i looked around here and learned more in a few days than in the last few years. By the way, I still earn my money with the internet – since 1995.

  8. Hellöle, thanks for the great guide. That all worked for me too. It's just stupid that the record keeps getting thrown out after a while. Especially if the first backup is to be created, that's stupid. Does anyone have similar experiences? I switched off the energy saving function, that doesn't seem to be the cause.

    Have a MacBook Pro with 10.11.6 & a Fritzbox 7590 with current FRITZ!OS: 07.25

    1. I have the same problem too! The disk is correctly integrated into TM, backup is started and simply aborted after an indefinite time! The energy-saving mode is deactivated in the Fritzbox settings! Does somebody has any idea?

  9. Hallo,
    it works great, thanks for the guide.
    I do have a small request: in the Finder, the image only shows a size of 4 GB and the disk on the Fritz.Box only seems to be occupied by this size - but the TimeMachine backup should be 150 GB in size. This also agrees with the availability that is displayed in Time Machine - and the backup also ran the entire GB. Where is the mistake? Can the Finder & FritzBox not measure the size of the image correctly or is the image really that small and the backup is not properly available?
    Best Regards

  10. I always get the error "Cannot connect to a recent Time Machine backup disk" at the very end when opening Time Machine. All previous steps worked without any problems. Does anyone have an idea or a similar problem?

    I use a FritzBox 7430 with FritzOS 7.21
    and a 2017 MacBook Pro running Big Sur 11.0.1

      1. What could be added to the super instructions would be the required release rights for the terminal. The terminal requires full disk access (security / data protection)

      2. After Mac OS Big Sur 11.3 update, the FritzNAS is no longer recognized.

        Do you have an idea what could be causing this?

  11. Thank you very much for the tutorial, it worked right away with Mojave and Fritzbox 7490.
    Quick question, I'm completely new to using Timemachine. Can I also back up two Macs to this volume / image now?
    Both in the same image or should I then create a second image in the same procedure on the volume on the Fritzbox?
    Can I automate the Fritz.Nas connect and mount image process? (Of course, just don't know how yet ;-)

    Thank you!

    1. Hello Christian,
      a little googling and trying later I can answer everything myself:
      In order to save two Macs to the disk on the Fritzbox via Timemachine, I have to create two sparse bundles. If I only have one, it can only be used by one computer at a time, which sounds logical.
      I created both bundles on one computer and integrated them using your method. Each computer accesses its own bundle and the image contained therein after mounting. The backups also run in parallel at the same time.

      As far as automatic mounting is concerned, it's very simple. After manual mounting, I make sure (Finder settings) that the Nas disk and the mounted image are displayed on the desktop.
      Then I go to Control Panels/Users and Groups/Login Items and drag both in there. Then it usually works after a restart. I can also hide the objects from the desktop again in the Finder settings.

      However, mounting the image vis login items did not work very reliably. So I tried whether I could also push the sparse bundle file into the login items (it's on the NAS disk, after all) and that works, the file is then opened automatically and the image is mounted as a result. Seems to be more stable that way.

      As an almost Mac newbie, I am very happy now, see you next time. ;-)

  12. Hello, I have already been able to set up a hard drive as a TimeMachine drive using the instructions described above and the current Labor version. I've been trying to do the same thing for a new hard drive for a few weeks, but to no avail. After entering "sudo tmutil setdestination /Volumes/TMSPARSE" I always get the following error"
    /Volumes/TMSPARSE: Invalid destination path. (error 22)
    The backup destination could not be set.

    I formatted the disk several times and created the image as instructed. The Fritzbox recognizes the plate. The Image/Sparsebundle file can also be opened manually in the Finder. Only setting the path no longer works. Can someone help me on this. I could also provide appropriate screen shots.

    1. Hi Hans,

      I have the same problem. Were you able to solve this problem in the meantime?

      Kind regards

      Oliver Setzer

      1. Hi Oliver,
        unfortunately not. It's a shame because that was a great solution. I'm grateful for any advice/reference in this matter.


    2. Hi,

      I had the same problem,

      /Volumes/TMSPARSE: Invalid destination path. (error 22)

      The backup destination could not be set.

      but was able to solve it: go through the steps to connect the disk, and then mount the TMSPARSE.sparsebundle.
      You should now find the individual Time Machine backup folders in the Backups.backupdb folder.

      In addition to the folders, I had an update that was "in progress". The file ends with ".inProgress". After I moved them to the recycle bin, the backup worked again as described in the article.

      Hope this helps!

  13. Setup works perfectly - very good idea with the nested image!

    Has anyone ever successfully restored a backup from the craft solution?

    1. I also used the method described and am just wondering how to restore the image with the created Timemachine backup. Finally, it has not yet been said whether the Mac Os Boot recognizes the image as a permissible storage medium.

  14. Unfortunately no longer possible at the moment, since AVM only supports the super old SMB1 and no SMB3. AVM For this:

    "In order to enable SMB access again, we are working on SMB3 support through FRITZ!OS and will provide this in an update for the FRITZ!Box. We cannot give a date for the update yet. Until the update is available, you can access the storage via or the FTP protocol, e.g. with Cyberduck"

    But this is not an alternative for Timemachine.

    1. With the current lab it is possible which supports SMB3. I have successfully integrated an EXT4 external hard drive and set it up as a TimeMachine data medium.

  15. Hallo,

    I did everything exactly as instructed. Mounting the sparse bundle worked, changing the destination in the terminal window too. But now when I try to open Time Machine, I get the error message "Cannot connect to a recent Time Machine backup disk".

    What am I doing wrong?

    1. Has done, I repeated the setup twice and got the same error message when opening. Now the backup just started in the background without any error message...

  16. Hallo,

    thanks for your tutorial. Actually everything worked fine so far. But in the terminal I always get the error message: Disk does not support Time Machine backups. (error 45)

    But the format is Mac OS Extended (Journaled)

    What could be the problem?

  17. Hello Christian,
    I was so happy to replace my old AirPort Extreme, which can no longer be used, with the FRITZ!Box 7430.
    Everything done as described. Show all devices, set TMDISK->FAT32->MBR.
    Creates a growing bundle image (APFS not Mac OS Extended).
    Mounted and tried in terminal to add as TM.
    Unfortunately, I get "Disk does not support Time Machine backups. (error 45)".
    Could it be the APFS?

      1. Yes, I was not at the computer to answer you. Yes, it's APFS, directly on the Mac, the corresponding drives even format to MacOS Journaled, because Time Machine can't handle it yet. Maybe in the next MacOS in autumn then...

        PS: Make sure you run a Time Machine on a normal USB drive, because the story might not be that reliable.

      1. I did it!

        1- Generate the .sparsebundle files in macos and put them in desktop.
        2- Format the USB Drive to ext4 in Windows.
        3- Connect the USB drive in Fritzbox.
        4- Simply upload the .sparse bundle through FRITZ-NAS.

        Finished! :)

        The next problem now... How to set up automouting for the sparse bundle?


  18. Hello and thank you for the guide. Sounds very useful. However, there are also Fritz.Boxes with internal memory. That's at least 1,5GB - which would be very suitable for backups. Unfortunately, you can't see this "HDD" in the hard disk utility, so I can't format it either.
    Do you have an idea with which hack this is possible?
    Thank you!

  19. Hallo,

    Thank you for the great instructions, coffee is on the way.

    However, I have one final problem. If I entered "sudo tmutil setdestination /Volumes/TimeMachine" the following error message appears after entering the password:

    /Volumes/TimeMachine: Invalid destination path. (error 22)
    The backup destination could not be set.

    what am i doing wrong

      1. Hallo,
        I assigned the names exactly as in the instructions, but I also get the error message!?
        What could be the problem?

      2. I had the same problem! Solution: when mounting it didn't name the drive correctly. I had to rename the mounted drive correctly again - et voila it worked...

  20. Hi! Unfortunately, I always get an error message when I try to connect to the server smb://fritz-nas... Where can this come from and how can I fix it? I have followed all the other instructions, and the plate was also recognized by the Fritzbox, I can't explain why. maybe someone here can think of something?

      1. Hallo,

        Question: I have set up the rights, then follow... Enter smb://fritz-nas as the server. Then click on "Connect". …. then a window opens to connect to the Fritzbox with a user and PW query. The Mac does not take the data stored in the FritzBox and therefore there is no mounting...! Where is my mistake, possibly assignment of rights on the Mac?

      2. Hallo,
        it could be your OS X version. The Fritz boxes use SMB1 while the latest versions of OS X only use SMB 3. I had the same error with my new MBP. There are Fritz AVM laboratory versions that support SMB 3.

  21. Hallo,
    First of all, thanks for the instructions, it worked great. I've got one more question.
    1. If I reset the Mac, is there a way to access the Time Machine backup via NAS or is that not possible?
    Greetings Leon

    1. The Mac should actually be able to find and use the backup during the new installation or when setting up via NAS. Otherwise that makes little sense ;) But as I said: DIY solution, no guarantee.

  22. Thanks for the tip. I got a lot of useful information from your site!

    Isn't that the way to set up a cloud?
    I am thinking of hanging an FP on the Fritze as you described and then the data with it
    Synchronizing ChronoSync – would that work?

    Greetings and have a nice Sunday.

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