Grub2 can't see partition on a MBR drive but can on GPT drives

Question

I have three hdds, the first two are formatted with GPT and the third MBR so as to boot windows when needed.  I have grub2 installed on /dev/sda and I can boot my Arch partitions just fine.  I can't however boot the windows partition (/dev/sdc1).  I can't even see the partition on it via grub2's console.  First, under Linux:
# fdisk -l /dev/sdc
Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000c14bc
Device Boot Start End Blocks Id System
/dev/sdc1 * 2048 122882047 61440000 7 HPFS/NTFS
/dev/sdc2 122882048 1953523711 915320832 83 Linux
Now in the grub2 console:
grub> ls
(hd0) (hd0,6) (hd0,5) (hd0,4) (hd0,3) (hd0,2) (hd0,1) (hd1) (hd1,2) (hd1,1) (hd2)
Note that there are no entries for (hd2,1) and (hd2,2) for some reason.  Is this because my first two drives are GPT formatted and grub isn't loading a module for MBR... or?
/etc/grub/grub.cfg
# DO NOT EDIT THIS FILE
# It is automatically generated by /sbin/grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
load_env
fi
set default="0"
if [ ${prev_saved_entry} ]; then
set saved_entry=${prev_saved_entry}
save_env saved_entry
set prev_saved_entry=
save_env prev_saved_entry
set boot_once=true
fi
function savedefault {
if [ -z ${boot_once} ]; then
saved_entry=${chosen}
save_env saved_entry
fi
set menu_color_normal=light-blue/black
set menu_color_highlight=light-cyan/blue
insmod ext2
set root='(hd1,1)'
search --no-floppy --fs-uuid --set f20eb010-e657-4364-acd0-45ed3f9f20c1
if loadfont /usr/share/grub/unicode.pf2 ; then
set gfxmode=1024x768x24
insmod gfxterm
insmod vbe
if terminal_output gfxterm ; then true ; else
# For backward compatibility with versions of terminal.mod that don't
# understand terminal_output
terminal gfxterm
fi
insmod ext2
set root='(hd0,5)'
search --no-floppy --fs-uuid --set 0fc7ed20-0b1e-4e26-860c-6e63dd3a35ea
insmod png
background_image ($root)/grub/genesis.png
fi
insmod ext2
set root='(hd0,5)'
search --no-floppy --fs-uuid --set 0fc7ed20-0b1e-4e26-860c-6e63dd3a35ea
set locale_dir=($root)/grub/locale
set lang=en
insmod gettext
set timeout=5
### END /etc/grub.d/00_header ###
### BEGIN /etc/grub.d/10_linux ###
menuentry "Arch Linux, with Linux vmlinuz26-ck" --class archlinux --class gnu-linux --class gnu --class os {
set gfxpayload=keep
insmod ext2
set root='(hd0,5)'
search --no-floppy --fs-uuid --set 0fc7ed20-0b1e-4e26-860c-6e63dd3a35ea
echo Loading Linux vmlinuz26-ck ...
linux /vmlinuz26-ck root=/dev/disk/by-uuid/f20eb010-e657-4364-acd0-45ed3f9f20c1 ro quiet
echo Loading initial ramdisk ...
initrd /kernel26-ck.img
menuentry "Arch Linux, with Linux vmlinuz26-ck Fallback" --class archlinux --class gnu-linux --class gnu --class os {
set gfxpayload=keep
insmod ext2
set root='(hd0,5)'
search --no-floppy --fs-uuid --set 0fc7ed20-0b1e-4e26-860c-6e63dd3a35ea
echo Loading Linux vmlinuz26-ck ...Loading Linux Fallback ...
linux /vmlinuz26-ck root=/dev/disk/by-uuid/f20eb010-e657-4364-acd0-45ed3f9f20c1 ro quiet
echo Loading initial ramdisk ...
initrd /kernel26-ck-fallback.img
menuentry "Arch Linux, with Linux vmlinuz26" --class archlinux --class gnu-linux --class gnu --class os {
set gfxpayload=keep
insmod ext2
set root='(hd0,5)'
search --no-floppy --fs-uuid --set 0fc7ed20-0b1e-4e26-860c-6e63dd3a35ea
echo Loading Linux vmlinuz26 ...
linux /vmlinuz26 root=/dev/disk/by-uuid/f20eb010-e657-4364-acd0-45ed3f9f20c1 ro quiet
echo Loading initial ramdisk ...
initrd /kernel26.img
menuentry "Arch Linux, with Linux vmlinuz26 Fallback" --class archlinux --class gnu-linux --class gnu --class os {
set gfxpayload=keep
insmod ext2
set root='(hd0,5)'
search --no-floppy --fs-uuid --set 0fc7ed20-0b1e-4e26-860c-6e63dd3a35ea
echo Loading Linux vmlinuz26 ...Loading Linux Fallback ...
linux /vmlinuz26 root=/dev/disk/by-uuid/f20eb010-e657-4364-acd0-45ed3f9f20c1 ro quiet
echo Loading initial ramdisk ...
initrd /kernel26-fallback.img
### END /etc/grub.d/10_linux ###
### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" --class memtest86 --class gnu --class tool {
insmod ext2
set root='(hd0,5)'
search --no-floppy --fs-uuid --set 0fc7ed20-0b1e-4e26-860c-6e63dd3a35ea
linux16 ($root)/memtest86+/memtest.bin
### END /etc/grub.d/20_memtest86+ ###
### BEGIN /etc/grub.d/30_os-prober ###
menuentry "Arch (on /dev/sda4)" {
insmod ext2
set root='(hd0,4)'
search --no-floppy --fs-uuid --set f1c45bf7-5da9-4010-89dc-04d2016a6373
linux /boot/vmlinuz26 root=/dev/sda4
initrd /boot/kernel26.img
menuentry "Windows 7 (loader) (on /dev/sdc1)" {
insmod ntfs
set root='(hd2,1)'
search --no-floppy --fs-uuid --set 1b03a3fc528a9b6c
chainloader +1
### END /etc/grub.d/30_os-prober ###
### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###
### BEGIN /etc/grub.d/40_custom.pacsave ###
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom.pacsave ###

Answer 1

Your problem is that the MBR module of grub2 is not loaded.
Try
menuentry "Windows 7" {
    insmod part_msdos
    insmod ntfs
    set root=(hd2,1)
    chainloader +1
Manually in the grub2 prompt try
grub> insmod part_msdos
grub> ls
(hd0) (hd0,6) (hd0,5) (hd0,4) (hd0,3) (hd0,2) (hd0,1) (hd1) (hd1,2) (hd1,1) (hd2) (hd2,2) (hd2,1) # your output should be like this
grub-install when setting up grub2 in the mbr (meaning the 1st 440 bytes boot code region alone) region detected GPT partition map in your system and copied that module alone to the core.img, not MBR (msdos) module. Hope this helps.
Last edited by skodabenz (2010-11-23 13:53:28)