Time Machine: "Oldest backup: None," "Latest backup: None" after temporarily changing backup disk

Joshua5684 wrote:

I've been using an external USB hard drive attached to my iMac shared over the network as my MacBook Time Machine. I was testing if I could do something similar using my Windows desktop as the server. In doing so, I had to change my Time Machine disk in my MacBook's Time Machine settings. I'm done testing and now I want to go back to using my iMac as the server, but when I select the disk, it shows as the title suggests. When I open the backupbundle file, I can see the all of the backups are there, but it seems that my MacBook TimeMachine app is not detecting them.

I've tried "Verifying Backups" but nothing changes.

I presume if I start a backup, it'll make a whole backup instead of an incremental one, which is undesirable.

What should I do?

Try holding the Option key and click open the TM icon in the menu bar, see if "Browse Other Backup Disk" gets you any closer

Joshua5684 wrote:

I've been using an external USB hard drive attached to my iMac shared over the network as my MacBook Time Machine. I was testing if I could do something similar using my Windows desktop as the server. In doing so, I had to change my Time Machine disk in my MacBook's Time Machine settings. I'm done testing and now I want to go back to using my iMac as the server, but when I select the disk, it shows as the title suggests. When I open the backupbundle file, I can see the all of the backups are there, but it seems that my MacBook TimeMachine app is not detecting them.

I've tried "Verifying Backups" but nothing changes.

I presume if I start a backup, it'll make a whole backup instead of an incremental one, which is undesirable.

What should I do?

Leroy has provided some good suggestions on trying to recover your Time Machine history.

FYI, in the future, there is no need to disconnect from the existing Time Machine backup when you want to try a new Time Machine disk. Time Machine will happily back up to multiple disks, it just cycles through them for the backups, "taking turns" so to speak. So you could leave the old one working with its full history while trying a new disk.

Joshua5684 wrote:

I was testing if I could do something similar using my Windows desktop as the server. In doing so, I had to change my Time Machine disk in my MacBook's Time Machine settings. I'm done testing and now I want to go back to using my iMac as the server...

When I do that, the disk I want shows up as it does already, but when I select it, it still says "Oldest backup: None" and "Latest backup: None."

Starting over would be the way to resolve your current issue.

general Trouble Shooting—

 https://support.apple.com/guide/mac-help/time-machine-troubleshooting-mh15653/mac

Always recommend to have a robust backup plan, example:

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

If you value your user data you should never be in a situation where you are desperate to recover a single backup source.

Time Machine is great when it works, not so much when it does not.

Time Machines strong point is that it creates recursive backups—enabling you to restore a specific file or the entire drive— from a certain point in time. It is not consider archival since when the disk gets full it starts to prune the oldest data.

Joshua5684 wrote:

Because the files are there. If I had deleted my old backups, I'd agree with you, but since the problem is of identification rather than data loss, I don't think it makes sense to start over. There must be some way to force it to use the existing backups.

Try some the suggestions here http://oldtoad.net/pondini.org/TM/17.html or use other parts of that suite of Time Machine help pages, keeping in mind that Pondini created this guide several MacOS versions ago and it has not been updated in years (the author, Pondini, passed away in 2013 but he was a great resource for Time Machine use).

Joshua5684 wrote:

Start over, as in, create a new backup?

Sure, why not.