A simple script to put in /etc/grub.d/ which makes iso files show up in your grub. This allows you to boot from iso files and use those for reinstalling your computer instead of using an external disk. :) You may need to alter variables to match your platform and the partition containing the iso files needs to be mounted during installation from…

GRUB Boot from ISO

#!/bin/sh
#Written by Remco Haszing: https://plus.google.com/u/0/101152546828331333610/
#Original post: https://plus.google.com/101152546828331333610/posts/8iaeaqd7hhz

for iso in /opt/iso/*.iso; do
    if [ "`isoinfo -f -i $iso | grep '/CASPER/VMLINUZ.EFI;1'`" == "" ]; then
        vmlinuz=vmlinuz
    else
        vmlinuz=vmlinuz.efi
    fi

    iso=`basename $iso`
    echo Found iso $iso >&2

    cat <<EOF
menuentry "$iso" {
    loopback loop (hd0,1)/$iso
    linux (loop)/casper/$vmlinuz boot=casper iso-scan/filename=/$iso file=(loop)/preseed/ubuntu.seed
    initrd (loop)/casper/initrd.lz
}
EOF
done

Yep, done.