Well, that was a piece of piss. Blast the image onto an SD card, hook up the USB drive, fire up the Pi, let it sort itself out, find its IP address from the router, log in, change default passwords, partition and format the USB drive, set up users and shares, and bingo. Took less than half an hour, and it was all done through the web interface; I didn’t have to touch the command line once. I am very, very impressed indeed with Open Media Vault. Free software at its best.
Next task is to catalog and organise the zillions of photos and videos I have scattered around various cloud drives and external hard disks. Happily, I came across this nifty little utility, which seems to do it pretty much automagically. It’s worth springing the paltry 9 bucks to get the pro licence.