DokuWiki » Infrastructure » Disaster Recovery

h1. Grub2 disaster recovery

h2. Requirements

To install such a system you will need the following:

* Download @Fedora 18 Live DVD@ or a newer version of Fedora supporting Grub2 and burn it on an empty CDROM (the .iso can be found here: http://fedoraproject.org/get-fedora)

* a bootable CDROM-drive

alternatively you might use a bootable USB-drive created with the @Fedora LiveUSB Creator@

h2. Preliminary Note

It is assumed that

* the first harddrive (@sda@) is the system-drive.

* the root filesystem to be recovered is in a logical group/volume called @/dev/vp_p2600f18/lv_f18_root@

* the boot filesystem to be recovered is in a partition called @/dev/sda8@

These settings might differ for you, so you have to replace them where appropriate.

Some very important information is take from https://fermilinux.fnal.gov/documentation/tips/mount-bind-chroot

*Many times when you are fixing a machine, you need to chroot into it. Many of those times the programs you run (such as grub-install) will need the /proc, /dev, and /sys directories to be alive and well. This is when you need to use bind.*

h2. Start Fedora 18 Live DVD

list all partitions

<pre><code class="bash">

fdisk -l

</code></pre>

list all logical volumes

<pre><code class="bash">

lvdisplay

</code></pre>

create a base directory for the system to be rescued

<pre><code class="bash">

mkdir /mnt/f18

</code></pre>

mount the 'root'-filesystem

<pre><code class="bash">

mount /dev/vp_p2600f18/lv_f18_root /mnt/f18

</code></pre>

mount the 'boot'-filesystem

<pre><code class="bash">

mount /dev/sda8 /mnt/f18/boot

</code></pre>

bind the /proc, /dev, /sys into the to be rescued 'root'-filesystem

<pre><code class="bash">

mount -o bind /proc /mnt/f18/proc/

mount -o bind /dev /mnt/f18/dev/

mount -o bind /sys /mnt/f18/sys

</code></pre>

chroot and install Grub2

<pre><code class="bash">

chroot /mnt/f18

grub2-install /dev/sda

exit

</code></pre>

restart the machine and test the result