This article presents the available programs that can provide, with different technology, a virtualization of Linux computers. We define some usage criteria that allows the reader to chose the relevant virtualization technology according to its specific needs. We focus on the Linux-VServer technology, which is a very lightweight and effective technology for the regular Linux user not interested in Kernel hacking. The Linux-VServer project also supports additional security options and resources limitation that can be very useful. This is also the most mature open-source technology and several users have production servers using this technology for years now.