I.e. files that are at the same time a valid .iso and a valid disk image.
Basically you can add to a normal bootable .iso a MBR taking advantage of the fact that the MBR is first absolute (512 bytes) sector of the device whilst the CD/DVD bootsector is the 17th sector (2048 bytes).
A BIOS will chainload the MBR on hd-like devices (including USB sticks) or the CD/DVD bootsectors (on optical media), then Syslinux/Isolinux, or grub4dos or GRUB2 (among others) will do the rest (chainloading the kernel and initrd and boot the Linux.
I.e. files that are at the same time a valid .iso and a valid disk image.
Basically you can add to a normal bootable .iso a MBR taking advantage of the fact that the MBR is first absolute (512 bytes) sector of the device whilst the CD/DVD bootsector is the 17th sector (2048 bytes).
A BIOS will chainload the MBR on hd-like devices (including USB sticks) or the CD/DVD bootsectors (on optical media), then Syslinux/Isolinux, or grub4dos or GRUB2 (among others) will do the rest (chainloading the kernel and initrd and boot the Linux.