If I attempt to boot GRUB 2 on my laptop over a USB drive, GRUB hangs after the "Welcome to GRUB!" message. Both GRUB 2.00 and Bazaar trunk behave in the same way.

After it hangs, the PC fan spins up, and CTRL-ALT-DEL doesn't work.

This might be the same problem reported at comment #5 of this bug report: https://bugzilla.redhat.com/show_bug.cgi?format=multiple&id=805747

The laptop is model DV7-6190, Sandy Bridge-based with 8 GB RAM and switchable Ati/Intel graphics. Its BIOS is UEFI-based itself, but it only boots OSes in legacy mode.

The problem seems to be related to the BIOS' "USB legacy support", because if I boot GRUB from a CD, it works fine, and it can load Linux successfully. If I boot GRUB from a CD while having a USB drive attached at power up, it still works as long as I don't access the USB drive. For instance, if I type "ls" at the GRUB prompt, it will hang.

I installed GRUB with --debug-image=all, and the messages I get before the crash are:

| kern/disk.c:230: Opening 'hd0, msdos1' ...
| partmap/msdos.c: 181: partition 0: flag 0x80, type 0x7, start 0x800, len 0x12a18000
| Detecting ntfs ...

I tried renaming the i386-pc directory. This way, GRUB does start in rescue mode without crashing, even when booted via USB. I then tried to manually insmod some random modules. Some of them load, others crash the machine in the usual way.

Working: adler32, crypto, extcmd, hexdump, search_fs_uuid, terminal, time

Crashing: hashsum, lsusb, lspci, mmap, normal, search, usb

Hexdumping the crashing modules' files does work, so GRUB is able to load them before crashing.

Sometimes I also get this additional error message:

disk/i386/pc/biosdisk.c: 303: Read error when probing drive 0x82

but it doesn't crash the machine, and it doesn't always happen.