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Networked folder cannot be selected as Time Machine backup destination

I have 4 Macs that I would like to backup to a 10 TB drive connected to a 5th Mac on the network.

When selecting a Time Machine destination that is a shared folder on a networked Mac, the following error is displayed.

The selected network backup disk does not support the required capabilities. Please choose a different network backup disk.

The strange thing is that 3 of the Macs have no problem selecting the networked folder, and Time Machine has no problem backing up to that folder. The error described above is only displayed on one of the Macs.

Things I've tried:

Changing the file sharing settings of the Time Machine folder on the 5th Mac to use AFP, AFP and SMB, and SMB. No affect. (Apple recommends SMB.)
Connecting to the 5th Mac as a different user, including connecting as a user that one of the other Macs successfully connect as. No affect.
Creating a new user account on the problem Mac and trying to set up Time Machine using that user account. Same problem.

Posted on Dec 2, 2019 8:42 PM

Top-ranking reply

Mitchell Hoffmeyer Author

Level 1

15 points

Posted on Dec 2, 2019 8:57 PM

Solved it. The problem Mac was using Samba 2.1 to connect to the Time Machine folder. Other Macs were using Samba 3.02.

How to verify the problem Mac was using a different Samba version

Use the Finder to connect to the Time Machine folder on the networked Mac.
Open Terminal and enter "smbutil statshares -a"
Look for SMB_VERSION.

In my case, the Macs that could use Time Machine reported "SMB_3.02" and the problem Mac reported "SMB_2.1".

How to change the version of SMB (Samba) used for connecting to shared folders

Navigate to the top level of your Mac's system drive (Macintosh HD or whatever you've named it).
Make sure hidden files and folders are displayed. Press SHIFT-COMMAND-period if they are not displayed to toggle between show/hide.
Open the following folder: private/etc
Do a "get info" on the file named "nsmb.conf" and change the permissions of this file so that you have Read & Write privileges.
Open the "nsmb.conf" file in TextEditor or some other text editor program.
Change the line that says "protocol_vers_map=2" (version 2) to "protocol_vers_map=4" (version 3). Yes, set it to "4" in order to make the version change to 3.
Save the file, and restart your Mac. (A log out/in might work too.)

This procedure allowed my problem Mac to finally be able to select the shared Time Machine drive.

If you've seen the The selected network backup disk does not support the required capabilities. error message, I hope this solution works for you too.

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Networked folder cannot be selected as Time Machine backup destination

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