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<TITLE>RE: Xen 2.0 Virtual Machine</TITLE>
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<P><FONT SIZE=2>Brian Kelsay wrote:</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> I went and read most of the HOWTO on User-mode Linux and</FONT>
<BR><FONT SIZE=2>> I have to say, I'm not sure if it actually gives you a</FONT>
<BR><FONT SIZE=2>> good impression of a new kernel being able to run on your</FONT>
<BR><FONT SIZE=2>> hardware. The host kernel is still in the way. You use</FONT>
<BR><FONT SIZE=2>> virtual devices and filesystems. Sure, it's safe, but it</FONT>
<BR><FONT SIZE=2>> won't tell you definitively if the new kernel works on</FONT>
<BR><FONT SIZE=2>> your hardware. </FONT>
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<P><FONT SIZE=2>If you can boot to a UML kernel, you can work with whatever hardware the underlying kernel has compiled virtual device support for. The whole point is that UML doesn't work on hardware. It runs in usermode on top of a kernel which does.</FONT></P>
<P><FONT SIZE=2>Actually, I'm lying ;) One of the directions UML is moving toward is the ability to compile support for selective direct hardware access. Certain hardware resources could be dedicated to different UML instances. This would allow you to decide where you want to place the virualization performance vs. security etc. tradeoffs.</FONT></P>
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<P><FONT SIZE=2>> Now if you want to test other software on a specific</FONT>
<BR><FONT SIZE=2>> kernel without risking crashing the system, then this</FONT>
<BR><FONT SIZE=2>> appears to be the answer you've been looking for. Or</FONT>
<BR><FONT SIZE=2>> if you want to test features of a new kernel, then this</FONT>
<BR><FONT SIZE=2>> would work. If you want to host an app like a webserver</FONT>
<BR><FONT SIZE=2>> in a controlled/limited environment, giving near root</FONT>
<BR><FONT SIZE=2>> privileges to a user, then this may work also, but a</FONT>
<BR><FONT SIZE=2>> chrooted jail might be better. Then again, I could be</FONT>
<BR><FONT SIZE=2>> wrong.</FONT>
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<P><FONT SIZE=2>Sure... use the right tool for the job.</FONT>
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<P><FONT SIZE=2>I just meant to underscore that chroot isn't always the right tool for the job. It depends on what you mean by a test environment, and whether or not the test environment needs root privileges.</FONT></P>
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<P><FONT SIZE=2>> User-mode appears to use less resources than a Xen, VMWare</FONT>
<BR><FONT SIZE=2>> or Bochs, as does chroot, but that is Linux on Linux only.</FONT>
<BR><FONT SIZE=2>> Each can have its place.</FONT>
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<P><FONT SIZE=2>You're preaching to the choir ;-)</FONT>
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<P><FONT SIZE=2>--</FONT>
<BR><FONT SIZE=2>Garrett Goebel</FONT>
<BR><FONT SIZE=2>IS Development Specialist</FONT>
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<P><FONT SIZE=2>ScriptPro Direct: 913.403.5261</FONT>
<BR><FONT SIZE=2>5828 Reeds Road Main: 913.384.1008</FONT>
<BR><FONT SIZE=2>Mission, KS 66202 Fax: 913.384.2180</FONT>
<BR><FONT SIZE=2>www.scriptpro.com garrett at scriptpro dot com</FONT>
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