install Buster on 120gb usb

[Joe Curtis]

I have a RPI 3B2+ running under Stretch from a 120gb USB which I would like to upgrade to Buster. I understand that it is best to install Buster from scratch but if I write the Buster image directly to the USB, will it boot from there (bearing in mind that the boot from USB bit is already set on the RPI) or do I have to go through the microSD route first?

[B.Goode]

if I write the Buster image directly to the USB, will it boot from there

Yes.


But of course it will irreversibly overwrite ALL the existing content of the usb storage device: System, configuration, documents, projects... In that sense it is NOT an 'upgrade', it is a new installation of a more recent release of the Operating System.

[Joe Curtis]

Thanks, I understand that, but I've had considerable trouble trying in-situ upgrades on other machines with MicroSD's that I have decided that the 'install from scratch option' having backed up my data is the only sensible way forward.

[B.Goode]

Thanks, I understand that, but I've had considerable trouble trying in-situ upgrades on other machines with MicroSD's that I have decided that the 'install from scratch option' having backed up my data is the only sensible way forward.

That is the recommended course of action from Raspberry Pi themselves. I see no reason to disagree...