rpi4-debian-nfsroot.txt

- Install a Debian filesystem using debootstrap on your NFS server (normal x86
  Linux machine, for example):

  $ debootstrap --arch=arm64 sid /home/pi

- Install qemu-aarch64 on host system and set up binfmt_misc to allow for
  chroot

  - depends on host system; Fedora and Arch have packages for this
  - no need to get arm64 libraries on host as the chroot will take care
    of this (but qemu binary should be static)

- Set up via chroot:
  - chroot arm64-root/
  - vim /etc/fstab: add nfs root

	  10.1.1.1:/home/pi / nfs rw,tcp,nolock 0 0

  - set root password; add users
  - install a kernel

	  apt install linux-image-5.9.0-4-arm64

  - install other packages as desired

- Add rpi to DHCP config (this is OpenBSD dhcpd syntax; adjust if needed):

    host pi.my.network {
      hardware ethernet 01:23:45:67:89:ab; # your Pi's MAC here
      fixed-address 10.1.1.2;              # your chosen IP address here
      option host-name "pi.my.network";
      allow booting;
      allow bootp;
      option tftp-server-name "10.1.1.1";
      option bootfile-name "bootcode.bin";
      option dhcp-class-identifier "PXEClient";
      option vendor-encapsulated-options "Raspberry Pi Boot";
    }

- Set up tftp on machine named by tftp-server-name
  - create a directory /var/lib/tftpboot/<RPi serial>
    (watch the logs the first time to find this path)
  - in this directory, extract the latest rpi4 firmware
    - should see a bunch of *.dtb files and start*.elf
  - copy vmlinuz and initrd.img from Debian filesystem's /boot
  - create config.txt:

      hdmi_safe=1
      arm_64bit=1
      upstream_kernel=1
      dtoverlay=upstream-pi4
      kernel=vmlinuz-5.9.0-4-arm64
      initramfs initrd.img-5.9.0-4-arm64-netboot followkernel

  - create cmdline.txt:

      root=/dev/nfs nfsroot=10.1.1.1:/home/pi console=tty1 rootwait

- optional: readonly NFS root (allows sharing between multiple Pis):

  - edit fstab: rw -> ro for NFS mount
  - add fstab entries:

      none /tmp tmpfs defaults 0 0
      none /var/tmp tmpfs defaults 0 0
      none /var/log tmpfs defaults 0 0
      none /var/run tmpfs defaults 0 0