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User profile for user: ShadowDancer1000
ShadowDancer1000 Author
User level: Level 1
54 points

Time Machine can't connect to the backup disk / OSStatus error 2

I run my TimeMachine backs up wirelessly to my back-up drive attached to my router. Once configured, I've had no problems.


About 24 hours ago I received a pop-up notice from TM that my back-up drive was not formatted in APFS. This has never mattered or been an issue. I closed the notice and instructed TM to run an immediate back-up. The process appeared to start, until the progress bar stopped about 1/2 way and I received another notice that the process could not be completed.


I power cycled my Mac and my back-up drive. The next attempt to reconnect to my back-up drive (which it can see) was met with this message:

"Time Machine can't connect to the backup disk. The operation couldn't be completed. (OSStatus error 2.)"



I'm now stuck at this point. Power cycles. attempts to reset have not changed the outcome. I still receive the "OSS" error message. Doesn't anyone know what's going on?



MacBook Pro

Posted on Aug 24, 2019 8:27 PM

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User profile for user: Barney-15E
Barney-15E
User level: Level 10
117,088 points

Posted on Aug 25, 2019 7:17 AM

You are using an unsupported backup method. It will never work reliably.

These are the only supported backup methods: Backup disks you can use with Time Machine - Apple Support

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User profile for user: ShadowDancer1000
ShadowDancer1000 Author
User level: Level 1
54 points

Sep 19, 2019 9:46 PM in response to Barney-15E

I cannot speak to why the solution worked, but it did.

Below are screen shots of the back-up I am running at this very moment.


I will note that after circling back on your comment re: ExFat not supported, that Disk Utility recognizes my TM partition as MacOS Extended Journal. I cannot emphasize enough that this is NOT what I reformatted the partition in. I chose exFAT.


The only reason I tried exFAT was after attaching a different back-up drive to the router, one which was solely formatted in exFAT for my Windows machine, TM's set-up and initialization process had no problem recognizing the drive through my router and backing up - which in turn is what gave me the idea to reformat the previous backup drive partition to exFAT.


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User profile for user: ShadowDancer1000
ShadowDancer1000 Author
User level: Level 1
54 points

Sep 19, 2019 7:29 PM in response to ShadowDancer1000

After some tinkering around I was able to find the solution.

The Time Machine partition had to be re-formatted in exFAT. Ever since I did the reformat 2 weeks ago, wireless TM over an ASUS router has been working as intended and reliably.


Note: Under no circumstance can the partition be formatted in APFS; APFS not supported by TM.

While exFAT is not the newest, shiniest format (introduced in 2006) it is well supported.

It will allow encryption and in an emergency you can even access the back-up with a Windows machine.


Good luck to all who encounter this issue and find this post in archives. I hope it helps.



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User profile for user: dot.com
dot.com
User level: Level 4
2,455 points

Sep 20, 2019 1:13 PM in response to ShadowDancer1000

If you look closely at the image you posted -- notice that Disk Utility says it's a "disk image volume" which makes me think that a sparse bundle was created on the exFAT formatted volume and that disk image is mounted and used by TM. If you mount that disk drive directly onto the Mac, and look at it's contents, I would guess that you see some sort of file named xxx.dmg.


So, technically you are using an HFS volume, as the sparse image after mounting appears as that type of filesystem which is what TM is then using. It's just a file on the physical drive that is formatted as exFAT.


In fact, while the TM backup is actually happening, do the following in a Terminal window:


diskutil list


and I bet you will see a volume mounted from the router with a big long name that will show what it's using.


Good luck...

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Time Machine can't connect to the backup disk / OSStatus error 2

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