Time Machine and Same Username Bug

We have a couple high capacity drives attached to a Mac mini running macOS Server on High Sierra. Family Macs use Time Machine to back up to these drives. At some point, my wife’s password on her Mac (running Mojave) changed from what was on the mini and Time Machine began to error out. Some foreshadowing: she uses the same username on the mini and her Mac.

After her password on the mini changed, her Time Machine backups displayed the following error messages:

“There was a problem connecting to the server”
“Time Machine can’t connect to the backup disk”
“OSstatus error 65”

Basic troubleshooting called on me to make a manual connection using Finder (command K) from her Mac to the mini – mounting the drive was successful, so I went back to Time Machine and tried from there, but the same errors above barfed out. Frustrating.

From Terminal on my wife’s Mac, I pasted in the following line:

log show --predicate 'subsystem == "com.apple.TimeMachine"' --info | grep 'upd: (' | cut -c 1-19,140-999

I pasted output from the command into Google and came across this post on Apple’s site:

https://discussions.apple.com/thread/7898878

Yes, Satrop’s issue and fix is it! The username on my wife’s Mac is identical to the username on the mini and somehow this disturbs things if the password changes. To get around this issue, I decided to use the following workaround, which is essentially changing the credentials on her Mac for how it mounts the mini. From her Mac I had to:

1. Disable Time Machine by System Preferences->Time Machine->Select Disk…->(click the disk you’re trying to mount)->Remove Disk.

2. In Keychain.app, remove all instances of the saved password to your NAS, in my case the mini. I searched for “mini” and “10.0.1.125” and deleted those instances.

3. From Finder, mount the mini’s disk (Command K) using my own credentials, which obviously differ from hers.

4. After the disk mounts, go back to System Preferences->Time Machine->Select Disk…->(select the mounted disk – I used AFP to mount the disk, so when I hovered over it I could see its address had the AFP protocol).

5. Success! When you quit Time Machine preferences, it should automatically start a new backup (or continue an existing one).

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