grub: “Missing Operating System”

Question

I tried editing the menu.lst file in order to dual-boot with Windows 7. I simply uncommented the Windows entry and added

map (hd0) (hd1)
man (hd1) (hd0)

according to the Arch Linux wiki. I rebooted and had a Grub menu with 3 options: Arch Linux, Arch Linux Recovery, Windows 7. Exactly as it should be. I selected Windows 7 and nothing happened. I hit Ctrl-Alt-Del and rebooted. Instead of grub, I got "Missing Operating System".

Using the Arch Live USB flash drive, I mounted the /boot/ partition (/dev/sda1) and discovered that I couldn't even get into the grub directory to look at or fix things. The output of cd /mnt/boot and ls -l is:

EXT2-fs (sda1): error: ext2_get_inode: unable to read inode block - inode=10041, block=41221
ls: cannot access grub: Input/output error
total 13667
d????????? ? ?    ?          ?            ? grub
-rw-r--r-- 1 root root 8411722 May  2 19:37 kernel26-fallback.img
-rw-r--r-- 1 root root 1764873 May  2 19:37 kernel26.img
drwx------ 2 root root   12288 May  2 19:12 lost+found
-rw-r--r-- 1 root root 1545080 Apr 22 18:32 System.map26
-rw-r--r-- 1 root root 2198640 Apr 22 18:32 vmlinuz26

So something about trying to boot to Windows seems to have destroyed grub, after things were going so well. (NB: With the 2nd (Windows) drive attached but not represented in menu.lst, Arch worked fine, booted properly, could mount and read partitions on the other drive.)

I can't show you the menu.lst file because I can't see it. It had not been changed from the default except to uncomment the Windows entry and add the two lines given above.

Out put of fdisk -l:

Disk /dev/sdb: 1000.2 GB...
...

       Device Boot     Start       End     Blocks  Id  System
/dev/sdb1              1         5      40131  de  Dell Utility
/dev/sdb2              6      1327   10614784   7  HPFS/NTFS
/dev/sdb3   *       1327     63517  499537920   7  HPFS/NTFS
/dev/sdb4          63517    121602  466567168   f  W95 Ext'd (LBA)
/dev/sdb5          63517    121602  466566144   7  HPFS/NTFS
Warning: invalid flag 0x0000 of partition table 5 will be corrected by w(rite)

Disk /dev/sda: 1000.2 GB...
...

   Device Boot     Start       End     Blocks  Id  System
/dev/sda1              1         5      40131   6  FAT16
/dev/sda2              6      1327   10614784   7  HPFS/NTFS
/dev/sdb3   *       1327     63517  499537920   7  HPFS/NTFS
/dev/sdb4          63517    121602  466567168   f  W95 Ext'd (LBA)

I notice that the partition information for sda1-4 are exactly the same as sdb1-4, which they should not be.

Also, I can't seem to mount anything from sda except /dev/sda1/, which contains the boot files and the unresponsive grub directory. If I do, I'm told mount: you must specify the filesystem type. If I specify -t ntfs, it fails and says it doesn't have a valid NTFS. If I specify -t ext4 (which is what it should be), it says it's the wrong fs type.

I can't think of any other details to include.

Answer 1

From the live CD, run the commands:

/lib/udev/vol_id /dev/sda2
/lib/udev/vol_id /dev/sda3
/lib/udev/vol_id /dev/sda4

And observe the output. If it did not recognize the partition type, then most probably the partition is corrupted.