Note: This note was originally in the Raspberry Pi, overlayfs read-write root, read-only NFS base post.
This setup described in the article above also works without the NFS setup.
As we plan to have no 'proper' storage and RAM limits the size of writes we can store there's no point having a swap file.
sudo dphys-swapfile swapoff sudo dphys-swapfile uninstall sudo update-rc.d dphys-swapfile remove
Update Ubuntu and the firmware, etc:
sudo apt-get update sudo apt-get dist-upgrade sudo apt-get upgrade sudo BRANCH=next rpi-update
Create the initramfs:
sudo mkinitramfs -o /boot/initrd
Add the script and make it executable.
sudo curl https://gist.githubusercontent.com/paul-ridgway/d39cbb30530442dca416734c3ee70162/raw/c490df8be1976dd062a8b5f429ef42ed1b393ecb/ro-root.sh -o /bin/ro-root.sh sudo chmod +x /bin/ro-root.sh
initramfs initrd followkernel ramfsfile=initrd ramfsaddr=-1
And now reboot again and it's done, the changes made to the original script to use
/etc/fstab seem to work in both cases.