OS backup duplicate names
 

I use SD! to make backups of my Catalina (10.15.7) OS drive; they are named "MB2OSXBkp1" and "MB2OSXBkp2". Both backups are volumes within an APFS container on an external HD. When I restart and hold the option key, the "choose start volume" screen shows four drives, named "MB2OSXBkp1", "MB2OSXBkp2", "MB2OSXBkp1", and "MB2OSXBkp2". If I choose either of the first two, boot fails, with the big "Ø", followed by boot to the normal drive. If I choose either of the second two, boot proceeds normally and the system volume ends up being as expected. Why are there duplicate drive names, and how can I get rid of them? I recently upgraded to Catalina.

I don't know where the extra ones are coming from: if you (or we) delete volumes, any support informations should go with it. But certainly if you fully erase the drive (from the hardware) and then re-copy, they'll go away.

I'll try the erase trick. Actually, I was wondering whether this is yet another instance of Catalina's being somewhat half-baked (e.g., the silly removal of Mail column customization). There are two volumes (or some similar entity) for each backup, the main one and the "... - Data" one. Maybe the restart code never got updated to take account of that change.

Good advice! I wasn't sure what you meant by "erase from the hardware", but I used Disk Utility to remove the volume (it automatically removed both parts of the linked OS backup volume, the main one and the "Data" one); I added back a new (single-part) volume in Disk Utility; used SD! to erase then backup (it created the second part, of course); and now option-restart shows only a single disk to boot from and it boots just fine.

Glad to hear it..