Grub Rescue

 In grub you will see a prompt like this.

grub and grub rescue has slight variations in commands.If you have grub-rescue shell,skip to the end.

grub>

grub> set pager=1

no space between = and 1;it invokes pager for large command outputs.

grub> ls
(hd0) (hd0,msdos2) (hd0,msdos1)

The ls commands shows all partitions.This may vary from computer to computer.
But you will see similar listing of partitions

grub> ls (hd0,1)/


lost+found/ bin/ boot/ cdrom/ dev/ etc/ home/  lib/
lib64/ media/ mnt/ opt/ proc/ root/ run/ sbin/
srv/ sys/ tmp/ usr/ var/ vmlinuz vmlinuz.old
initrd.img initrd.img.old

ls on every partition till you find an output like this.This is the root file system.

grub> cat (hd0,1)/etc/issue
Ubuntu 14.04 LTS \n \l

Use cat to read etc file to dermine the linux if you have multiple linuxes.


Booting From grub>

if root file system is on (hd0,1) and vmlinuz-3.13.0-29-generic(The third line sets the initrd file, which must be the same version number as the kernel.).
And if you have (hd0,1) then root=/dev/sda1;
If you have hd0,1 = /dev/sda1. hd1,1 = /dev/sdb1. hd3,2 = /dev/sdd2.


grub> set root=(hd0,1)
grub> linux /boot/vmlinuz-3.13.0-29-generic root=/dev/sda1
grub> initrd /boot/initrd.img-3.13.0-29-generic
grub> boot


If this didn't work then,try these.

grub> set root=(hd0,1)
grub> linux /vmlinuz root=/dev/sda1
grub> initrd /initrd.img
grub> boot


But if you are on grub rescue then commands vary

grub rescue> set prefix=(hd0,1)/boot/grub
grub rescue> set root=(hd0,1)
grub rescue> insmod normal
grub rescue> normal
grub rescue> insmod linux
grub rescue> linux /boot/vmlinuz-3.13.0-29-generic root=/dev/sda1
grub rescue> initrd /boot/initrd.img-3.13.0-29-generic
grub rescue> boot



Making Permanent Repairs

When you have successfully booted your system, run these commands to fix GRUB permanently:

Caution: Third Line from bottom grub-install /dev/sda.Don't use sda1 or anyother number after it.you
may use sdb but don't include any number


# update-grub
Generating grub configuration file ...
Found background: /usr/share/images/grub/Apollo_17_The_Last_Moon_Shot_Edit1.tga
Found background image: /usr/share/images/grub/Apollo_17_The_Last_Moon_Shot_Edit1.tga
Found linux image: /boot/vmlinuz-3.13.0-29-generic
Found initrd image: /boot/initrd.img-3.13.0-29-generic
Found linux image: /boot/vmlinuz-3.13.0-27-generic
Found initrd image: /boot/initrd.img-3.13.0-27-generic
Found linux image: /boot/vmlinuz-3.13.0-24-generic
Found initrd image: /boot/initrd.img-3.13.0-24-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
done
# grub-install /dev/sda
Installing for i386-pc platform.
Installation finished. No error reported.










Learn python for fun.The popular blog with questions and answers to the python.Solutions to facebookhackercup,codejam,codechef.The fun way to learn python with me.Building some cool apps.