User-mode Linux (UML) is the port of Linux to Linux. It has demonstrated that the Linux system call interface is sufficiently powerful to virtualize itself. However, the virtualization isn't perfect, in terms of individual UML performance, aggregate performance of a number of UML instances sharing a host, or, in one way, functionality.

This paper discusses the current weaknesses in the ability of Linux to host virtual machines and proposes some ways of correcting those shortcomings.

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