iSCSI boot and XEN hypervisor

[robinsmidsrod]

I'm a bit confused. Did you install the Xen hypervisor on the machine that is iSCSI-booted? If you're using iPXE and sanboot to boot this machine, then I'm going to assume a different kernel+initrd is in use. It might also be a bug in the Ubuntu initramfs when used together with iSCSI boot and Xen. I'd suggest you use just text console and increase the debug level to ensure you actually see the kernel log as you boot. Most likely you're getting some kind of kernel panic because of the Xen/iSCSI boot interaction.

If you're able to get into grub and the kernel is able to execute then I think this might be a Linux/Ubuntu problem, not an iPXE problem. I'd suggest you try and grab some debug information and post it here.