RPi ROM on SD card, hard disk image on USB thumb drive

Is there any way to have a RPi ROM on the SD card, but the disk image on USB thumb drive as with RISC OS 5.18 on a BBxM?

I’d prefer to be able to do this as I have a collection of (old, small and slow) SD cards which I want to use to have different versions of RISC OS on, and some fast big USB thumb drives which work well on my BBxM.

If I have to use the RPi SD card for both ROM and disk image then I have to make sure that all my SD cards have a complete disk image on them as well. If I add components to !Boot then I have to remember to copy !Boot to all other SD cards to keep it up to date.

It should just be a question of using the correct configure options, like booting from SCSI on an RPC, for example.

Something like “Configure filesystem scsi”
I just tested it and it works.

This came in handy when I had to change my boot location on a BB-xM:

Have you done *OPT 4,2 on the new drive to make it bootable?
From the supervisor prompt try: -
*conf.files.scsifs
*conf.scsifsdr.4
*dir scsi::4.$
*opt 4,2
*!boot
Then restart.

(depending on what number your SCSI drive has of course!)

Thanks for the replies. So far I have been unable to get my RPi to boot from a USB thumb drive. Tomorrow is another day.

The crucial thing is to set the configured filesystem as scsi. It will then boot off the pen drive. To check whether you have succeeded in writing the ‘new CMOS values’ to the SD card, do a *STATUS command after the next boot and see whether ‘filesystem’ still says ‘SDFS’ or whether the change to ‘SCSI’ has taken effect. Opt 4,2 is unnecessary on a pen drive.