How can I install Ubuntu on my Nexus 7 while being able to recover from an Nandroid backup?

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http://askubuntu.com – I use CyanogenMod and ClockWork Recovery on my Nexus 7. How can my existing full nandroid backup be used to restore my device after installing Ubuntu? The instructions assume "recovery" would mean re-flashing the vanilla image, at factory, data-wiped condition. It would be useful to provide a .zip that can be flashed via Clockwork (or other) recovery usin ROM Manager or booting into recovery and back to whatever Nandroid backup there is - much as any other ROM is provided/used. (HowTos)