Grub

Sometime you can issue some problems with your grub often when your server dosen't want to start, there are no needs to reinstall it, just to fix your grub.

fix the GRUB from the startup command line

Normally if grub can not start and your system is nice, you have a minimum order prompt ... otherwise go to Chapter 2.

root (hd0,0)
Filesystem type is ext2fs, partition type 0xfd

setup (hd0)

Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 d (hd0)"... 16 sectors embedded
succeeded
Running "install /grub/stage1 (hd0) (hd0)1+16 p (hd0,0)/grub/stage2 /grub/grub.conf"...
succeeded
Done.

reboot

to /dev/sdb you implement of one, similar to the following disks (sdc, sdd, sde ....)

root (hd1,0)
setup (hd1)

We must install grub on all other drives to give the capacity to operate the system. to reach the boot menu of the bios, well it depends on your hardware ... F12 under dell, Acer Esc, F11 from msi .... my sme is with Raid1 so I have two drives, you will need to adapt my example to your the number of disks.

fix the GRUB with the systemrescuecd

	Note:
	We go to work with SystemRescueCd which is a Linux system rescue disk available as a bootable CD-ROM or USB stick for administrating or repairing your system and data after a crash.Download. The goal is to get mounted your logical volumes on /mnt where you can save them on a usb disk.

• start the system with your system rescue cd or you usb stick, choose your keyboard settings

• then start the server X

startx

• open a terminal to verify if your raid is initiated.

cat  /proc/mdstat

• if you are lucky the output will look like this

# cat /proc/mdstat 
Personalities : [raid1] 
md99 : active raid1 sdb1[1] sda1[0]
      104320 blocks [2/2] [UU]
      
md100 : active raid1 sdb2[1] sda2[0]
      262036096 blocks [2/2] [UU]
      
unused devices: <none>

• so we need to launch the LVM

vgchange -ay

• afterward if the LVM is launched without error messages, we can mount the LVM in /mnt

	Tip:
	if you have a name of logical volume who is not /dev/main/root, you can type this command for knowing all your logical volume, and adapt this to your configuration.

lvdisplay

• Now you have successfully mounted your LVM then do this

mkdir /mnt/sysimage
mount /dev/main/root /mnt/sysimage
mount -o bind /dev /mnt/sysimage/dev
mount -o bind /proc /mnt/sysimage/proc
chroot /mnt/sysimage /bin/bash

• We will have to mount the /boot of your system, which is normally contained in / dev/md1.

To do this you must send a

cat /proc/mdstat

• note the md(X) the smallest (about 100 megs) then in your root terminal do this:

mount /dev/md(X) /boot

and then

grub
root (hd0,0)
setup (hd0)

you can restart and continue the tutorial

Installation of grub on the other disks

• once your Sme started, you need to login in Root

then type

grub

device (hd0) /dev/sda

root (hd0,0)

setup (hd0)

device (hd1) /dev/sdb

root (hd1,0)

setup (hd1)

quit

• same for other drives, you implement one each time

from there you can reboot your server and check that the grub is installed on each hd. it is simple, with the boot menu or bios, you say on what hd you want to boot . to reach the boot menu of the bios, well it depends on your hardware ... F12 under dell, Acer Esc, F11 from msi ....