Introduction
These pages describe how to setup your computer to dual, or multi-boot Ubuntu, with another instance of Ubuntu, and additional operating systems.
Back Up Your Data
First, backup your data files and settings to an external backup medium (ex. USB hard drive) before attempting any kind of changes.
Recovery CD for existing operating system
It is best to have OEM provided external recovery media prior to making any changes to your hard drive. If you don't have any please contact your vendor for support.
Some Cases
Most operating systems during install automatically check for other currently existing operating systems. They then add the existing ones into a boot-menu along with the new one so that you can choose which OS to boot into. However, Windows does not.
General Case
Usually you already have an existing OS which you use. As you go through the Ubuntu installer you reach a section called "Partitioning Section", this offers you a choice to install Ubuntu alongside your existing OS. This does all the work for you. When you reboot the machine you get to a menu with these choices:
- Ubuntu
Ubuntu in recovery mode = housekeeping & handy fix-it tools
- Old OS 1
- Old OS 2 (if you are making a multi-boot rather than just a dual-boot)
- Memtest
- There might be other options
If you installed Ubuntu first and a different OS last then the menu will look something like this:
- non-Windows other OS
- Ubuntu
- Memtest (usually)
- There might be other options
So, if Ubuntu is not installed last then the "recovery mode" is missed but can be edited into the list.
Windows
For instructions on Windows, please see here.
Mac
Please see section 4 of this guide on Mac Dual-boot. The Mac guide is not as complete as the sections for other Operating Systems but i think it is being worked on.
Xen Server
There is a guide but also this question might help. Note at the end it mentions using "chainloader"