Boot into the system in question and in order to determine the grub version, in a terminal run the command:

sudo grub-install --version

or if that fails try:

sudo grub2-install --version

If this returns "GNU GRUB version 0.97" (possibly with a custom suffix), then it is using GRUB (otherwise called GRUB legacy) not GRUB2 and your system should be correctly identified by Mageia during installation and added automatically to the menu.

If this returns (GRUB) 1.98 or 1.99 or 2.xx, then you are using GRUB2.

Make a note of the version and enter this command to identify the root partition:

df /

This will output something like :

Filesystem Size Used Avail Use% Mounted on

/dev/sdb11 15G 7.0G 7.0G 50% /

The "sdb11" part is the root partition - make a note of it.

You can now shut down the system and install Mageia.

In your new running Mageia system, open a terminal and as root edit the file /boot/grub/menu.lst. as follows:

To become root use:

su

(enter root password)

To open the file in an editor use:

kwrite /boot/grub/menu.lst

(replace "kwrite" with "gedit" if you are using Gnome)

Add the following entry for your (e.g. Ubuntu) system possibly as the second stanza:

title Ubuntu

root (hd1,10)

kernel /boot/grub/core.img

If the GRUB2 version is 2.xx then change the last line to :

kernel /boot/grub/i386-pc/core.img

If you needed to use "grub2-install" earlier then change /grub/ to /grub2/ in the last line.

Save the file and re-boot. You should now see your "Ubuntu" entry in the menu and be able to boot from it.