Virtualization with Xen

Xen is a the No. one choice for Virtualization in Open Source world.

some basic folders

/etc/xen/

/etc/vir

some useful commands

xm create -c /path/to/config - Start a virtual machine.
xm shutdown  - Stop a virtual machine.
xm destroy  - Stop a virtual machine immediately without shutting it down. 
              It's as if you switch off the power button. 
xm list - List all running systems.
xm console  - Log in on a virtual machine. 
              Ctrl-] or Ctrl-5 to leave the guest console
xm help - List of all commands.

Network bridge, we could create a new bridge based on eth0 or some other interface.  Here is a reference: http://forums.oracle.com/forums/thread.jspa?threadID=968625

$ /usr/sbin/brctl addbr xenbr0
$ /sbin/ip link set xenbr0 up
# Think first before using addif, it may hang up the eth0
$ /usr/sbin/brctl addif xenbr0 eth0

Xen networking is a very complex topic, here is a wiki page about it from xen.org: http://wiki.xensource.com/xenwiki/XenNetworking

Here are some interesting talking about KVM, VirtualBox, and VMWare: http://www.linuxaria.com/article/kvm-virtualbox-o-vmware?lang=en

Xen in multi-processor machine

This section is trying to answer the question about how to allocate processors to different xen guest vms.