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[Solved] Time Machine using MacMini connected drive  



I have headless MacMini 2018 being currently setup as a server for my home.  I have portable hard drives connected for media (Plex), misc data, and a Time Machine backup drive.  The TM drive is currently being used for the MacMini and I would like to use it for a wirelessly connected backup drive for my MacBook Pro.

I have found how to add the drive to the shared list and even opted into using it as a Time Machine destination.  The problem is when I try to use it on the MacBook Pro.  I select the drive and then it asks for the user information.  I've tried all the options and either they fail or say:

You do not have the necessary read, write and append privileges on the selected network backup disk.

I have added myself as a read/write user and even gone as far as to give the Guest user the same options and tried using Guest.  I've tried using my Login Name and Apple ID selection and always get the same result. 

This is the first time I've setup this type of system so I'm not sure what I have overlooked.

Any help would be greatly appreciated.

2 Answers

I suspect, repeat... I have a suspicion, that the issue may be you're trying to allocate (ie share) the whole drive for this function (Time Machine network destination) rather than a particular folder on the drive?

As mentioned above by @datafornothinandbitsforfree, Time Machine backing up over the network is less than reliable - but it is certainly much more convenient than plugging in an external drive & remembering to eject that drive before unplugging. So certainly you can use the Mac Mini as a TM destination, but also have another backup mechanism in place.

That was the problem.  After I added a folder in the drive and set that folder inside the drive as the MBP backup it worked.  Thank you for the quick reply.


A) my history with using a Mac mini as a Time Machine network back device has not been good.  I'll explain in a bit.


B) You need to use an Admin account when connecting to the Mac mini in order to mount the Time Machine file system.  Read/Write access is not enough, as you will need to have permission to change file ownership on the Mac mini and only an admin can do that. 


When I used my Mac mini as my Time Machine network backup device, my Time Machine backup file kept getting corrupted, mostly because I would pick up my Macbook Pro, close the lid and take it out of the house.   This interrupts the backup, possibly in the middle of doing some file system metadata operation, corrupting the Time Machine backup.  While this does not happen often, statistically when I'm doing this 5 days a week when I'm going to work, taking my Macbook Pro with me, it eventually happens.


The important thing to keep in mine, when Time Machine is backing up across the network, it is creating a Sparse Bundle disk image and the Macbook Pro is treating that Sparse Bundle as a local file system and the Macbook Pro is doing all the metadata operations on the Sparse Bundle.


When it happens, the Macbook Pro ends with Time Machine preparing, which under the covers was the Macbook Pro running fsck_hfs to repair the Time Machine backup, but it would never end.


Years ago, I stopped using Time Machine over a network.  I still use Time Machine with desktop Macs (such as the Mac  mini that is always running, and my iMac, and my Mom's iMac), but for Mac laptops, I had switched to CrashPlan until last year when they discontinued the ability to use your own systems, and now I'm using Carbon Copy Cloner across the network to the Mac mini.


Since the Mac mini is in charge of the file system, closing the Macbook Pro lid and taking it out of the house does not mess with the file system, nor interrupt any file system metadata operations because the Mac mini is still up and running.


While I use CCC, there are other solutions you could use as well.

I just want to be clear about my Carbon Copy Cloner use.  It is going across the internet to the Mac mini in the basement with a Drobo attached.  I use the Source is a "Remote Macintosh" and let the Mac mini pull the files from the Macbook Pros (1 for me and 2 for my wife).


But I can also use the Destination is a "Remote Macintosh" and push the files from a Macbook Pro to the Mac mini.


I use Carbon Copy Cloner's scheduling so this happens automatically.


The network connection is over an encrypted secure shell (ssh) connection.


If you play the right kinds of games with your home router and port forwarding, you can even backup across the internet.  I also backup my Mom's iMac 300 miles away using this approach.


I agree with @kiwigraham that attaching a physical disk to the Macbook Pro and then de-attaching, wash, rinse, repeat is a pain that often times stops happening just before you need it the most.