Updating from Catalina to Big Sur am getting Checking "(null") and Incompatible Disk messages

Thank you for the helpful response. I am trying to rebuild my teenage grandson's machine - clogged with the residues of 100 video games. I am not an expert and the help has been very welcome. In the end I have succeeded by:

> Taking care to go back and erase absolutely everything in each of the volumes; the first attempt seemed to have left a few GB behind - maybe contributing to the Incompatible Disk message

> NOT using the Reinstall option in the Recovery App (which took me to Mojave) - and expecting to "climb back" through the updates.

> Instead, do a new Restart and use the Option-Command-R route (See Reinstall macOS webpage) to install the latest compatible OS - taking me direct to Big Sur. This seems to have dodged round the Checking "(null)" message.

> This worked - but I got messages suggesting that my WiFi link was not working; maybe I could have persisted, but in line with your message I used an ethernet connection (Happily I have a USB/ethernet adaptor)

> I am left with two "surplus" volumes which have "turned up" so I will need to tidy them up.

Thank you again

Hi,

I can see the "surplus" internal Volumes in Disk Utility (Apps/Utilities) but I can't erase or delete them there. The additional Volumes seem to be a by-product of the OS Restore processes - where I tried several routes. Back at the start of my "clean-up" process I managed to erase the original Volumes (though in two steps), and also to delete one unwanted Volume, using the Disk Utility in the Recovery App.

So I will go back to the Recovery App to remove the unwanted Volumes. Hope this makes sense

A

Hi,

Thank you for your concern

I think I'm OK now - and have avoided doing anything really silly

Thank you again

A