User Mode Linux

User Mode Linux

User Mode Linux is a way of running more instances of Linux on your existing Linux system. It runs as a program, called simply, linux. It might help to see a picture:

{{{  __________________________ |                          | |      Linux (host)        | |   ________________       | |  |                |      | |  |   User Mode    |      | |  |     Linux      |      | |  |________________|      | |__________________________|

}}}

Why would anyone want to do that?

It’s a safe way to test things without installing Linux on another machine, or fiddling with disk partitions or having to reboot your working machine. For example you might want to:

• Try out a different distribution
• Play with the latest kernel
• Design network layouts involving many machines and learn more about networking
• Find out what happens when you do something silly and then work out how to recover from it

OK, How Do I Get Started?

There is a wealth of information available on the UML development website and UML community website

If you’re using Debian, SimonCapstick has written a very easy to follow guide, available in RTF and PDF that will get you started.

Simon now has a couple more guides in RTF and PDF format about using SKAS mode. SKAS, or Separate Kernel Address Space, is a patch to the kernel, to keep kernel and process memory separate. It means that it is harder to tell if a Linux system is running UML – very useful if you would like to run a honeypot.

Instructions on how to build Debian root filesystems with rootstrap using the packages in your APT cache. Written by GrahamBleach.