How to fix boot into initramfs prompt and “mount: can’t read ‘/etc/fstab’: No such file or directory” and “No init found”?

Installing a new system using a GPT partitioned disk dedicated to a single partition, ext4 formatted, extlinux (version 4.05) as bootloader, Ubuntu Core version 13.10 amd64 as rootfs, and Ubuntu linux-image-3.11.0-18-generic as kernel, and extlinux-update to generate bootloader configuration.