"User-Mode Linux (UML) is a Linux virtual machine
running on Linux that allows you to boot Linux on a "software"
machine. These virtual machines can be easily created and
destroyed, and allow you do do virtually anything that can be done
with a physical system. Because of this, UML has turned out to have
a wide variety of uses. In this article, I will talk about an
application that has not received anywhere near the attention I
think it deserves.
UML virtual machines are nearly identical to physical machines
in their behavior, except that they are far more convenient to
configure and boot. This makes them ideal for system administrator
training and practice. In particular, they are very well-suited for
creating admin disasters in order to practice recovering from them.
I will be describing the creation of and recovery from three
disasters, plus the creation (but not recovery) of a fourth.
To get started, you will need to download UML and install it. Go
to http://user-mode-linux.sourceforge.net/dl-sf.html and grab and
install either the UML RPM or deb, whichever is appropriate for
your system. These will install UML itself, plus a number of
utilities. You will also need a filesystem image to boot UML on.
These are available from the same page. I will be using the Debian
root filesystem in the examples below. If you are too short of
bandwidth to download that one, get the tomsrtbt filesystem