I have two Macintosh HD volumes and how can I merge them on my MacBook Air

Tugweston wrote:

Somehow, during an attempt to upgrade my MacBook Air from Catalina to sonoma, I have ended up with an extra Mackintosh HD volume.

I have 2x Mackintosh HD volumes and one Mackintosh HD - Data volume. Why would this be? Can I delete one without loss of data? Can I merge these two HD volumes into one?

i keep getting message that I have insufficient space to upgrade so wonder if the fact that I have 2 volumes probably mounted in different locations is the issue.

Can you post a screenshot of disk utility showing all of that?

You cannot merge, nor would there be anything to actually merge, in the two Macintosh HD volumes.

You just need to figure out which one is not your start up volume and remove the other in Disk Utility

Until you can provide us with that Disk Utility screenshot, the most likely reason this happened is that you attempted to install macOS Sonoma inside an existing APFS Volume and not in an APFS Container.

If you were using Disk Utility as part of this process, did you make sure that you used the "Show All Devices," and not "Show Only Volumes" view?