Dual Boot - Grub2 not detecting Ubuntu Server (10.4, 64 bit) after installing Ubuntu Desktop (12.04)

Requirement
I have a computer which runs Ubuntu 10.4.3 (64 bit server) installed over LVM and /boot filesystem and I wanted it to dual boot to Ubuntu 12.04 (desktop, 32 bit).

Completed Successfully:

1. Creating a free partition to installed desktop version- Followed procedures/discussions in this question and freed up 200 GB out of 200GB hard disk. This was successful.





2. Installing Ubuntu 12.04.1 desktop version (32 bit) - Successfully installed OS iun to newly created free space as /dev/sda6 (extended)

The problem:

1. During install, Desktop version failed to see Ubuntu Server's presence and asked me if I want to use who system. I used manual install to over come install correctly.




2. Grub did not detect my Ubuntu Server install and set it up directly to boot to Ubuntu 12.04.

What I tried to fix this:

1. I used Grub2 recovery procedures described in this question using Ubuntu 12.04.2 64 bit server CD and could get only server install back. Grub did not detect my desktop version in a different partition.




2. I used the same procedures with Desktop CD and then Grub only detected and installed my desktop version, did not detect my server version.

Edit 1

3. Downloaded rescatux CD and tried to 'Update GRUB configuration' and 'Restore Grub'. Update Grub configuration failed when I chose the LVM and succeeded when I chose sda6 (non-lvm ubuntu 12.04) and restore grub forced me to choose one partition and depending upon the partition I choose, I could boot only that version linux.
   Question
   How to get this to boot as dual boot option ?

Try to use Boot-Repair Tool.

Many cases of problems relating to the boot are a mal-function or bad-installation of Grub or something related to the MBR and partition table, noticing that Boot Repair Tool was created aiming to give an easy way to fix this common problem, recommended by Ubuntu team.

Obs.: If you don't get access to the internet during use of Boot-Repair you won't get the URL mentioned below that can give us important details about your problem in case the recommended repair doesn't work.

Install Boot-Repair in Ubuntu

In your case, as you are able to boot to Ubuntu, you can install boot repair with these commands:

This step can be followed through Live-CD/DVD/USB's "Try Ubuntu" section too

sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
sudo apt-get install -y boot-repair && (boot-repair &)

Then, start Boot-Repair and just click the "Recommended repair" button. When repair is finished, note the URL (paste.ubuntu.com/XXXXX) that appeared on a paper, then reboot and check if you recovered access to your OSs.

If the repair did not succeed, indicate the URL to us as it will give us more information about the error.

Get a CD including Boot-Repair

This way is for who isn't able to start any installed OS in the computer, there are two options:

1. Use this ISO to create a bootable Live-CD/USB of Boot-Repair Tool


2. Boot your pc from Linux Security Remix where Boot-Repair Tool will be included by default

Choose one of the optionsm start Boot-Repair and click the "Recommended repair" button. When repair is finished, note the URL (paste.ubuntu.com/XXXXX) that appeared on a paper, then reboot and check if you recovered access to your OSs.

If the repair did not succeed, indicate the URL to us as it will give us more information about the error.

For more details and info about advanced options please read this Ubuntu help page.