C.4 Giving Each User a Virtual Machine
If users cannot afford dedicated
machines, it's possible
to provide each user with a virtual machine, assuming that you have a
very powerful server that can run a few virtual machines on the same
hardware.
There are a number of virtual-machine technologies, both commercial
and open source. Here are some of them:
The User-Mode Linux kernel gives you a virtual machine that may have
different hardware and software virtual resources than the physical
computer. Disk storage for the virtual machine is entirely contained
inside a single file on the physical machine. You can assign your
virtual machine only the hardware access you want it to have. With
properly limited access, nothing you do on the virtual machine can
change or damage your real computer or its software. If you want to completely protect one user from another and yourself
from your users, this is yet another alternative to the solutions
suggested at the beginning of this chapter.
For more information, visit the home page of the project at
http://user-mode-linux.sourceforge.net/.
VMWare technology allows you to run a few instances of the same or
different operating systems on the same machine. This technology
comes in both open source and commercial flavors. The open source
version is at
http://savannah.nongnu.org/projects/plex86/. The
commercial version is at http://www.vmware.com/. VMWare will allow you to run a separate OS for each of your clients
on the same machine, assuming that you have enough hardware
resources.
freeVSD (http://www.freevsd.org/) is an open
source project that enables ISPs to securely partition their physical
servers into many virtual servers, each capable of running popular
hosting applications such as Apache, sendmail,
and MySQL. The S/390 IBM server is a great solution for huge ISPs, as it allows
them to run hundreds of mod_perl servers while having only one box to
maintain. The main drawback is its very high price. For more
information, see
http://www.s390.ibm.com/linux/vif/.
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