After jsg@ mentioned that booting a Raspberry Pi 3 from a USB device might be possible, I decided to find out how deep the rabbit hole is. As it turns out, it's currently a bit convoluted, but it can be made to work with OpenBSD. First off, USB boot support is just now getting fully ironed out. You'll need to update the firmware on your Pi to make it work. I installed the latest (2017-03-02) Raspbian image to an SD card and booted the Pi from that. While booted in Raspbian, update the firmware:
sudo apt-get update sudo apt-get install rpi-update sudo rpi-update It's then necessary to actually enable USB boot support. Add the following 2 lines to /boot/config.txt to enable USB boot mode and set a 5-second timeout to allow time for USB device initialization: program_usb_boot_mode=1 program_usb_boot_timeout=1 NOTE: Apparently these variables are set in the Pi's OTP memory, which means once they're set, they can't ever be unset. Reboot for the changes to take effect. At this point the Pi should be ready to support USB booting. While you still have a working Raspbian install, grab a copy of the /boot/bootcode.bin and /boot/start.elf files for later use; apparently we need these special versions of those two files for USB boot support. At this point we're done with Raspbian and can shut it down to install OpenBSD. Next, write the OpenBSD miniroot60.fs to an SD card, plug in your USB drive, and boot the Pi. You should be greeted with the usual OpenBSD installer, and you should be able to install to your USB drive (probably sd0). Once the installer is done, run 'halt', unplug the Pi, and remove the SD card and USB drive. To make your USB drive bootable, you'll need to plug it into another system and mount its 'i' partition (the FAT32 boot partition) to make a few changes. Replace the bootcode.bin and start.elf files with the ones from Raspbian, and add the u-boot.bin file from the 'i' partition of your miniroot60.fs SD card. With those changes made, your Pi should be able to boot OpenBSD directly from a USB drive with no SD card needed. Note that it seems to take around 10 seconds for the Pi to reach the OpenBSD bootloader and fire up the kernel. Hope this information is helpful to someone... -- Joe Gidi j...@entropicblur.com "You cannot buy skill." -- Ross Seyfried
