1) I have the two hard disk, /dev/sda and /dev/sdb.
2) When Both Hard disks are present it is booting Perfectly.
a) When I remove the Second Hard disk /dev/sdb I got " Operating system not found"
b) When I remove the First Hard disk I got "Grub"
Reason:1) Booting files /boot/grub/grub.conf are located in /dev/sda
2) MBR Grub is located in /dev/sdb
Some Other criteria
1) Hard disk does not contain the any Operating System,
Due to this only we got the following Error Message.
Operating System Not Found -Error Message
SolutionTo resolve this problem First we have to change the grub MBR into First hard Disk.
1) First I boot From Linux CD the Rescue mode.
2) Rescue Mode mount Hard disk File system under /mnt/sysimage
Try the following command to resolve
If File you Got "Error 15: File not found" then try
Then You will get like (hd0,0) or (hd0,4)
It will install grub Boot loader in (hd0,0)
Then restart the server your system will be booting perfectly. Operating System not found. Grub Error-How to Resolve.