Xen
===
To manage xen domains with libvirt you have to set:

(xend-unix-server yes)

in /etc/xen/xend-config.sxp.

For xend HTTP access (not recommended) you also have to set:

(xend-http-server yes)
# only allow access from localhost:
(xend-address localhost)

Note that *every* user on the system has access to xend then. Better use
libvirtd to access xen with unprivileged users and add the users to the
"libvirt" group (see "Acess Control" below).

Debugging
=========
Use LIBVIRT_DEBUG=1 to enable libvirt's debugging output, e.g.:

LIBVIRT_DEBUG=1
export LIBVIRT_DEBUG
virt-manager

The default NAT network
=======================
To ease network configuration libvirt defines a NATed network named "default".
VMs using this network end up in 192.168.122.1/24 and DHCP is provided to them
via dnsmasq. This network is not automatically started. To start it use:

 virsh net-start default

To make the default network start automatically use:

 virsh net-autostart default

In order for things to work this way you need to have the recommended packages
dnsmasq, bridge-utils and iptables installed. However Debian's default dnsmasq
configuration conflicts with the way libvirtd wants to invoke it. You have two
possibilities:

    * don't start dnsmasq via /etc/init.d/dnsmasq during system startup and let
      libvirtd handle dnsmasq completely

    * use "interface=lo" and "bind-interfaces" in dnsmasq.conf 

See http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=504605 for more information.

Access Control
==============
Access to the libvirt socket is controlled by membership in the "libvirt" group.
If you want to manage VMs as non root you need to add a user to that group.

 -- Guido Guenther <agx@sigxcpu.org>  Thu, 15 May 2008 14:13:03 +0100