Linux Journal: User-Mode Linux: A Book Excerpt

“One of the largest efforts involved with software engineering
is testing the software to make sure that it works as designed.
Testing can require several different types of system
configurations and could require multiple instances of Linux. One
way to create this type of environment is to use a virtual
machine.

“User-Mode Linux (UML) is a fully functional Linux kernel. It
runs its own scheduler and virtual memory (VM) system, relying on
the host kernel for hardware support…”

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