OpenStack Configuration Example

From Xen

The SUSE Cloud project contains a fully operational OpenStack implementation for Xen Project. It is an example of how to successfully employ Xen Project in OpenStack. This page attempts to document the Xen Project-specific configuration elements as an example of what a functional implementation might look like. As such, this page is less a "How To" and more a "What Is".

Where to Find the Configuration Files

The bulk of the Xen Project-specific entries will be in the Barclamp section of the Nova project within OpenStack. Most of these files can be found in the following trees:

Recipes files

The following portions are the Xen Project-specific segments from compute.rb:

def set_boot_kernel_and_trigger_reboot(flavor='default')
# only default and xen flavor is supported by this helper right now
 default_boot = 0
 current_default = nil

 # parse menu.lst, to find boot index for selected flavor'/boot/grub/menu.lst') do |f|
  f.lines.each do |line|
   current_default = line.scan(/\d/).first.to_i if line.start_with?('default')

   if line.start_with?('title')
   if flavor.eql?('xen')
    # found boot index
    break if line.include?('Xen')
    # take first non-xen kernel as default
    break unless line.include?('Xen')

  default_boot += 1

 when "xen"
  %w{kernel-xen xen xen-tools openvswitch-kmp-xen}.each do |pkg|
   package pkg do
    action :install

 service "xend" do
  action :nothing
  supports :status => true, :start => true, :stop => true, :restart => true
  # restart xend only when xen kernel is already present
  only_if { %x[uname -r].include?('xen') }

 template "/etc/xen/xend-config.sxp" do
  source "xend-config.sxp.erb"
  group "root"
  owner "root"
  mode 0644
   :node_platform => node[:platform],
   :libvirt_migration => node[:nova]["use_migration"],
   :shared_instances => node[:nova]["use_shared_instance_storage"],
   :libvirtd_listen_tcp => node[:nova]["use_migration"] ? 1 : 0,
   :libvirtd_listen_addr => Chef::Recipe::Barclamp::Inventory.get_network_by_type(node, "admin").address
  notifies :restart, "service[xend]", :delayed


The following portions are the Xen Project-specific segments from xen.rb:

node.set[:nova][:libvirt_type] = "xen"

Template Files

Note that these examples use libvirt to integrate into OpenStack, not XAPI (aka XenAPI). Many of these files have extensive XenServer integration logic based on XAPI; this is not pertinent here.

The following portions are the Xen Project-specific segments from nova.conf.erb:

# Whether to use cow images (boolean value)
<% if @libvirt_type.eql?('xen') -%>
<% else -%>
<% end -%>
# Libvirt domain type (valid options are: kvm, lxc, qemu, uml,
# xen) (string value)
# Deprecated group/name - [DEFAULT]/libvirt_type
virt_type=<%= @libvirt_type %>
<% if @libvirt_type.eql?('xen') -%>
<% if @libvirt_migration and @shared_instances -%>
# Migration target URI (any included "%s" is replaced with the
# migration target hostname) (string value)
# Migration flags to be set for live migration (string value)
# Migration flags to be set for block migration (string value)
<% end %>
# Override the default disk prefix for the devices attached to
# a server, which is dependent on virt_type. (valid options
# are: sd, xvd, uvd, vd) (string value)
# Deprecated group/name - [DEFAULT]/libvirt_disk_prefix
<%= "disk_prefix=xvd" if @libvirt_type.eql?('xen') %>
# Location where the Xen hvmloader is kept (string value)

The following portions are the Xen Project-specific segments from xend-config.sxp.erb:

(xend-unix-server yes)
<% if @libvirt_migration -%>
(xend-relocation-server yes)
<% else %>
(xend-relocation-server no)
<% end %>
<% if @libvirt_migration -%>
(xend-relocation-address '<%= @libvirtd_listen_addr %>')
<% else %>
(xend-relocation-address '')
<% end %>
<% if @libvirt_migration -%>
(xend-relocation-hosts-allow '')
<% else %>
(xend-relocation-hosts-allow '^localhost$ ^localhost\\.localdomain$')
<% end %>
<% if @node_platform == "suse" -%>
(network-script )
(vif-script vif-bridge)
<% else %>
(network-script network-bridge)
(vif-script vif-bridge)
<% end %>
(dom0-min-mem 256)
(enable-dom0-ballooning yes)
(total_available_memory 0)
(dom0-cpus 0)
(vncpasswd '')

The following portions are the Xen Project-specific segments from libvirtd.conf.erb: