You will need:
- A Pi 4B
- A USB-C power supply (probably the official one)
- An ethernet cable
- A microsd card
- An SSD, I used the Samsung T7 2TB
- A powered USB hub (THIS IS ABSOLUTELY REQUIRED OR YOU WILL HAVE TOTALLY UNPREDICTABLE FAILURES AND CORRUPTION)
Flash the SSD with the NixOS .img file you downloaded from Hydra (intended to flash on an sd card, but you can just flash it straight to the SSD using the following command):
(Obviously change the filename to the one you downloaded)
sudo dd if=nixos-sd-image-24.11pre635424.e8057b67ebf3-aarch64-linux.img of=/dev/sdb bs=4096 conv=fsync status=progress
Make sure you allow USB boot first with the RaspiOS official imager. Update the firmware first:
# nix-shell -p raspberrypi-eeprom
# mount /dev/disk/by-label/FIRMWARE /mnt
# BOOTFS=/mnt FIRMWARE_RELEASE_STATUS=stable rpi-eeprom-update -d -a
Then just flash the microsd card with the "change the boot order" image.
I did sd card first, then USB if sd card is missing. That way we can install using the sd card and then boot from USB once the install is complete.
Now update the config as detailed in these instructions here
For some reason when I did the rebuild I could no longer access the ethernet network.