Agnello George wrote:
now suppose i have Two OS install -- debian Etch and the centos ...and grub is the default boot loader ( and grub file is located in /etc/grub.conf ..which has instruction / menu screen for booting the various OS ) but i don't seem to understand one thing - How is /etc/grub.conf made available to the boot loader even before a OS is selected ( explanation not very clear in the article )
/etc/grub.conf?
Though there may be 2 or more OSes in a system, only one grub.conf or menu.lst is used to point to all these systems. The grub in the MBR simply points to the partition that contains the grub files and grub.conf or menu.lst. This list file contains entries of all the installed OSes.
You can manually alter grub to point to any OS's list file of your choice without any order of installation.
As an experiment you can boot a live Ubuntu cd by hitting F6 at the live boot menu, type 'single' without any quotes and hit enter. After the bootup, you will be taken to a root prompt. There run the command 'grub' and study it.