Explanation: Amazon Machine Images that use paravirtual (PV) virtualization use a system called PV-GRUB during the boot process. PVGRUB is a paravirtual boot loader that runs a patched version of GNU GRUB 0.97. When you start an instance, PV-GRUB starts the boot process and then chain loads the kernel specified by your image’s menu.lst file.
Reference:
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/UserProvidedKern…