Booting thru GRUB command line

Lately I have come across many questions , related to GRUB . Most common of the problems are
1. Installed windows after installing Linux , so there is no GRUB to boot to linux . How to get the grub ?
2. In case of GRUB failure , on a machine that has multiple OS , how to boot ?

Well in most of the cases , you have the #grub-install command that will do the job for you . But in order to run the command you need to be in linux env . And in case , where you are not able to boot in to linux might cause problems .

A simple solution for this is to have a grub floppy , that will help you boot in to required OS .

Or if you have a sloaris bootable disk , you get the grub along with it . So no need to try the floppy stuff. Boot from
cd/dvd , enter grub command line .. try the below options . .

ex: In this case if you want to boot into windows

grub> rootnoverify (hd0,0)
grub> makeactive
grub> chainloader +1
grub> boot

If you have more than one OS(in this example lets take Linux and Windows).
Then the kernel needs to be set  : boot to linux (in my machine Linux is at (hd0,4) so
grub> root (hd0,4)
grub> kernel /boot/vmlinuz-2.6.15-8-i386 ro root=/dev/
grub> initrd /boot/initrd-2.6.15-8-i386
grub> boot
 (Change the text in red to suite your system )

 Happy Booting :)