Magic ISO Image Booting with GNU GRUB 2
Recently I needed to prepare a USB thumb drive with several Ubuntu installations. A little research quickly yielded many setup instructions, for example like the one from Pendrivesystem.com . I was really surprised at how well this works and wanted to understand it better. In essence all recipes rely on GNU GRUB in version 2 and the loopback feature that it contains and on the OS's ability to work off an ISO image. The loopback command mounts a CD or HDD image that contains the kernel and initrd from an ISO image. As a result one can put several ISO images on the boot media without the need to extract them. The OS then also mounts the ISO image and uses that instead of a CD/DVD drive. So here is my version of the recipe, the USB thumb drive is in /dev/sdc in my examples: 1. partition & format device I prefer to partition the device with parted because it aligns the partition at 1MB so that it leaves enough space for GRUB to embed itself into the first sectors of