Deploy ISO Image as a File on a FAT32 Formatted USB Stick

In KIWI NG, all generated ISO images are created to be hybrid. This means, the image can be used as a CD/DVD or as a disk. The deployment of such an image onto a disk like a USB stick normally destroys all existing data on this device. Most USB sticks are pre-formatted with a FAT32 Windows filesystem, and to keep the existing data on the stick untouched, a different deployment needs to be used.

The following deployment process copies the ISO image as an additional file to the USB stick and makes the USB stick bootable. The ability to boot from the stick is configured through a SYSLINUX feature that allows you to loopback mount an ISO file and boot the kernel and initrd directly from the ISO file.

The initrd loaded in this process must also be able to loopback mount the ISO file to access the root filesystem and boot the live system. The dracut initrd system used by KIWI NG provides this feature upstream, called “iso-scan”. Therefore, all KIWI NG-generated live ISO images support this deployment mode.

For copying the ISO file to the USB stick and the setup of the SYSLINUX bootloader to make use of the “iso-scan” feature, an extra tool named live-grub-stick exists. The following procedure shows how to set up the USB stick with live-grub-stick:

  1. Install the live-grub-stick package from software.opensuse.org.

  2. Plug in a USB stick.

    Once plugged in, check which Unix device name the FAT32 partition was assigned to. The following command provides an overview of all storage devices and their filesystems:

    $ sudo lsblk --fs

  3. Call the live-grub-stick command as follows:

    Assuming “/dev/sdz1” was the FAT32 partition selected from the output of the lsblk command:

    $ sudo live-grub-stick {exc_image_base_name}.x86_64-1.15.6.iso /dev/sdz1

  4. Boot from your USB Stick.

    Activate booting from USB in your BIOS/UEFI. As many firmwares have different procedures on how to do it, look into your user manual. EFI booting from an ISO image is not supported at the moment. For EFI booting, use the –isohybrid option with live-grub-stick; however, note that all the data on the stick will be lost. Many firmwares offer a boot menu that can be activated at boot time. Usually, this can be reached by pressing the Esc or F12 keys.