Default:- default boot OS from list
Timeout:- how much time it’s wait for user selection, if not press any key then boot default OS.
Splashimage:- GUI of GRUB boot loader.
Title:- name of OS
root (hd0,0):- root partition on Hard disk.
Kernel:- which kernel load during boot.
To set run level in grub conf we put [ 1-5 ] in kernel parameter.
how to pass runlevel during boot time.
Press “e” to edit.
Again press “e” after select kernel part.
Put runlevel [ 1-5 ] in the end of kernel line with one space. Like “5”. Then press enter.
then press “b” to boot.
How to re-restore boot partition. [don’t run this command on running system ]
1st identify boot partition. Like “/dev/sda1”
Then boot OS in rescue mode with help of CD or ISO image.
Press “Esc” on this screen
Type “linux rescue” on command prompt.
Select “CD/DVD” from list.
Select “Network” No.
You can also re-set password of root user.