Booting Ubuntu 14.04 Live via iPXE on UEFI

[robinsmidsrod]

The additional initrd=initrd.lz on the kernel command line is because UEFI kernels load their ramdisks from a virtual filesystem, while legacy BIOS already has them described via a pointer provided to the booted kernel.

It might be useful to see the actual kernel panic message to figure out where to go from here. If you're getting a "missing root device"-type error then it is pretty obvious that your initrd is not loaded properly by the kernel. Are you sure you boot vbox in UEFI mode? You might have no issues because you're booting vbox in legacy bios mode and bare-metal in UEFI mode and your issue is purely visible in UEFI mode.