Installing GRUB using grub-install

go to linux rescue mode then.to reinstall grub.conf follow this one of the method..
1)check that grub.conf exists r not.
check in the cmd pmt about older kernel version,then install same kernel and enjoy...then automatically you will get grub.conf

if not then install grub by this method;
if it has server with nfs image then select user mode 1
for eg:
chroot /mnt/sysimage
grub install /dev/sda
exit
then type grub
grub> root (hd0,0)
grub> setup (hd0)
quit
restart