Mostly note to my self for future reference.

What they don’t tell You in the tar backup tutorial is that it’s not enough to edit /etc/fstab (and their instructions for grub are for grub-legacy).

Because after restoring you probably have new partition UUIDs, you must:

• boot livecd
• mount your root fs
• mount -B /dev /rootfs/dev, etc. (with proc and sys at least) to be able to chroot from livecd to your root fs
• chroot /rootfs
• edit /etc/fstab and change UUIDs there (new ones you can get using blkid
• do sudo dpkg-reconfigure -plow grub-pc to automatically upgrade grub config files, just let it install to the drive(s) it was on
• do update-initramfs -u so UUID stored inside initramfs get updated, too

Then you should be able to boot it.