224 lines
15 KiB
XML
224 lines
15 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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version="5.0"
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xml:id="xen_libvirt">
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<?dbhtml stop-chunking?>
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<title>Xen via Libvirt</title>
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<para>OpenStack Compute supports the Xen Project Hypervisor (or Xen). Xen can be integrated with
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OpenStack Compute via the <link xlink:href="http://libvirt.org/">libvirt</link>
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<link xlink:href="http://wiki.xen.org/wiki/Choice_of_Toolstacks">toolstack</link> or via the
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<link xlink:href="http://xenproject.org/developers/teams/xapi.html">XAPI</link>
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<link xlink:href="http://wiki.xen.org/wiki/Choice_of_Toolstacks">toolstack</link>. This
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section describes how to set up OpenStack Compute with Xen and libvirt. For information on
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how to set up Xen with XAPI refer to <xref linkend="section_hypervisor_xen_xapi"/>.</para>
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<section xml:id="xen-libvirt-install">
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<title>Installing Xen with Libvirt</title>
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<para>At this stage we recommend to use the baseline that we use for the <link
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xlink:href="http://wiki.xenproject.org/wiki/OpenStack_CI_Loop_for_Xen-Libvirt">Xen
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Project OpenStack CI Loop</link>, which contains the most recent stability fixes to
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both Xen and Libvirt.</para>
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<para><link
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xlink:href="http://www.xenproject.org/downloads/xen-archives/xen-45-series/xen-451.html"
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>Xen 4.5.1</link> (or newer) and <link xlink:href="http://libvirt.org/sources/"
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>Libvirt 1.2.15</link> (or newer) contain the most recent OpenStack improvements for
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Xen. The necessary Xen changes have also been backported to the Xen 4.4.3 stable branch
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(not yet released at this stage). Please check with the Linux and FreeBSD distros you
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are intending to use as <link
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xlink:href="http://wiki.xenproject.org/wiki/Category:Host_Install">Dom 0</link>,
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whether the relevant version of Xen and Libvirt are available as installable
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packages.</para>
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<para>The latest releases of Xen and libvirt packages that fulfil the above minimum
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requirements for the various openSUSE distributions can always be found and installed
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from the <link xlink:href="https://build.opensuse.org/project/show/Virtualization">Open
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Build Service</link> Virtualization project. To install these latest packages, add
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the Virtualization repository to your software management stack and get the newest
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packages from there. More information about the latest Xen and Libvirt packages are
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available <link xlink:href="https://build.opensuse.org/package/show/Virtualization/xen"
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>here</link> and <link
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xlink:href="https://build.opensuse.org/package/show/Virtualization/libvirt"
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>here</link>.</para>
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<para>Alternatively, it is possible to use the Ubuntu LTS 14.04 Xen Package
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<emphasis>4.4.1-0ubuntu0.14.04.4</emphasis> (Xen 4.4.1) and apply the patches
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outlined <link
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xlink:href="http://wiki.xenproject.org/wiki/OpenStack_CI_Loop_for_Xen-Libvirt#Baseline"
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>here</link>. You can also use the Ubuntu LTS 14.04 libvirt package <emphasis>1.2.2
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libvirt_1.2.2-0ubuntu13.1.7</emphasis> as baseline and update it to libvirt version
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1.2.15, or 1.2.14 with the patches outlined <link
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xlink:href="http://wiki.xenproject.org/wiki/OpenStack_CI_Loop_for_Xen-Libvirt#Baseline"
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>here</link> applied. Note that this will require re-build these packages partly
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from source.</para>
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<para>For further information and latest developments, you may want to consult the Xen
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Project's <link
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xlink:href="http://lists.xenproject.org/cgi-bin/mailman/listinfo/wg-openstack"
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>mailing lists for OpenStack related issues and questions</link>.</para>
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</section>
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<section xml:id="xen-libvirt-configuration">
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<title>Configuring Xen with Libvirt</title>
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<para>To enable Xen via libvirt, ensure the following options are set in
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<filename>/etc/nova/nova.conf</filename> on all hosts running the <systemitem class="service"
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>nova-compute</systemitem>
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service.<programlisting language="ini">compute_driver = libvirt.LibvirtDriver
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[libvirt]
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virt_type = xen</programlisting></para>
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</section>
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<section xml:id="xen-libvirt-additional-configuration">
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<title>Additional configuration options</title>
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<para>Use the following as a guideline for configuring Xen for use in OpenStack:</para>
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<orderedlist>
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<listitem>
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<para><emphasis role="bold">Dom0 Memory:</emphasis> Set it between 1GB and 4GB by
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adding the following parameter to the Xen Boot Options in the <filename><link
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xlink:href="http://xenbits.xen.org/docs/unstable/misc/xen-command-line.html"
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>grub.conf</link></filename> file.
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<programlisting language="ini">dom0_mem=1024M</programlisting></para>
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<note><para>Note that the above memory limits are suggestions and should be based on
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the available compute host resources. For large hosts, that will run many hundred of
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instances,the chosen values may need to be higher.</para></note>
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<note><para>The location of the grub.conf file depends on the host Linux
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distribution that you are using. Please refer to the distro documentation for
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more details (see <link xlink:href="http://wiki.xenproject.org/wiki/Category:Host_Install"
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>Dom 0</link> for more resources).</para></note>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Dom0 vcpus:</emphasis> Set the virtual CPUs to 4 and
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employ CPU pinning by adding the following parameters to the Xen Boot Options in the
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<filename><link
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xlink:href="http://xenbits.xen.org/docs/unstable/misc/xen-command-line.html"
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>grub.conf</link></filename> file.
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<programlisting language="ini">dom0_max_vcpus=4 dom0_vcpus_pin</programlisting></para>
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<note><para>Note that the above virtual CPU limits are suggestions and should be based on
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the available compute host resources. For large hosts, that will run many hundred of
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instances, the suggested values may need to be higher.</para></note>
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</listitem>
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<listitem>
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<para><emphasis role="bold">PV vs HVM guests:</emphasis> A Xen virtual machine can
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be paravirtualized (PV) or hardware virtualized (HVM). The virtualization mode
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determines the interaction between Xen, Dom 0, and the guest VM's kernel. PV guests
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are aware of the fact that they are virtualized and will co-operate with Xen and
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Dom 0. The choice of virtualization mode determines performance characteristics.
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For an overview of Xen virtualization modes, see
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<link xlink:href="http://wiki.xen.org/wiki/Xen_Overview#Guest_Types">
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Xen Guest Types</link>.</para>
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<para>In OpenStack, customer VMs may run in either PV or HVM mode. The mode is a
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property of the operating system image used by the VM, and is changed by
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adjusting the image metadata stored in the glance image service. The image
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metadata can be changed using the nova or glance commands.
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</para>
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<para>
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To choose one of the HVM modes (HVM, HVM with PV Drivers or PVHVM) use nova or
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glance to set the vm_mode property to hvm</para>
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<para>To choose one of the HVM modes (HVM, HVM with PV Drivers or PVHVM) use one of
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the following two commands
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<screen><prompt>$</prompt> <userinput>nova image-meta <replaceable>img-uuid</replaceable> set vm_mode=hvm</userinput></screen>
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<screen><prompt>$</prompt> <userinput>glance image-update <replaceable>img-uuid</replaceable> --property vm_mode=hvm</userinput></screen>
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To chose PV mode, which is supported by NetBSD, FreeBSD and Linux, useone of
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the following two commands
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<screen><prompt>$</prompt> <userinput>nova image-meta <replaceable>img-uuid</replaceable> set vm_mode=xen</userinput></screen>
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<screen><prompt>$</prompt> <userinput>glance image-update <replaceable>img-uuid</replaceable> --property vm_mode=xen</userinput></screen>
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</para>
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<note><para>The default for virtualization mode in nova is PV mode.</para></note>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Image Formats:</emphasis> Xen supports raw, qcow2 and vhd
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image formats. For more information on image formats, refer to the <link
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xlink:href="http://docs.openstack.org/image-guide/content/ch_introduction.html"
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>OpenStack Virtual Image Guide</link> and the <link
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xlink:href="http://wiki.xenproject.org/wiki/Storage_options"
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>Storage Options Guide on the Xen Project Wiki</link>.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Image Metadata:</emphasis> In addition to the vm_mode property
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discussed above, the hypervisor_type property is another important component of the image
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metadata, especially if your cloud contains mixed hypervisor compute nodes. Setting the
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hypervisor_type property allows the nova scheduler to select a compute node
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running the specified hypervisor when launching instances of the image. Image
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metadata such as vm_mode, hypervisor_type, architecture, and others can be set
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when importing the image to glance. The metatdata can also be changed using the
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nova or glance commands:
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<screen><prompt>$</prompt> <userinput>nova image-meta <replaceable>img-uuid</replaceable> set hypervisor_type=xen vm_mode=hvm</userinput></screen>
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<screen><prompt>$</prompt> <userinput>glance image-update <replaceable>img-uuid</replaceable> --property hypervisor_type=xen --property vm_mode=hvm</userinput></screen>
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</para>
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<para>For more more information on image metadata, refer to the <link
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xlink:href="http://docs.openstack.org/image-guide/content/image-metadata.html"
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>OpenStack Virtual Image Guide</link>.
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</para>
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</listitem>
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</orderedlist>
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<para>To customize the libvirt driver, use the configuration option settings documented in
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<xref linkend="config_table_nova_xen"/>.
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</para>
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</section>
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<section xml:id="xen-libvirt-troubleshoot">
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<title>Troubleshoot Xen with Libvirt</title>
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<itemizedlist>
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<listitem>
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<para><emphasis role="bold">Important Log Files:</emphasis> When an instance fails to start, or when
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you come across other issues, you should first consult the following log files:
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<itemizedlist>
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<listitem><para><filename>/var/log/nova/compute.log</filename> (for more information refer to
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<xref linkend="section_nova-logs"/>).</para></listitem>
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<listitem><para><filename>/var/log/libvirt/libxl/libxl-driver.log</filename>,</para></listitem>
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<listitem><para><filename>/var/log/xen/qemu-dm-${instancename}.log</filename>,</para></listitem>
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<listitem><para><filename>/var/log/xen/xen-hotplug.log</filename>,</para></listitem>
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<listitem><para><filename>/var/log/xen/console/guest-${instancename}</filename> (to enable see <link
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xlink:href="http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen#Guest_console_logs"
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>Enabling Guest Console Logs</link>) and</para>
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</listitem>
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<listitem><para>Host Console Logs (read <link
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xlink:href="http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen#Host_console_logs"
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>Enabling and Retrieving Host Console Logs</link>).</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>If you need further help you can ask questions on the mailing lists <link
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xlink:href="http://lists.xenproject.org/cgi-bin/mailman/listinfo/xen-users"
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>xen-users@</link>, <link
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xlink:href="http://lists.xenproject.org/cgi-bin/mailman/listinfo/wg-openstack"
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>wg-openstack@</link> or <link
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xlink:href="http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen">raise a
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bug</link> against Xen.</para>
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</listitem>
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</itemizedlist>
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</section>
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<section xml:id="xen-libvirt-known-issues">
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<title>Known issues</title>
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<itemizedlist>
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<listitem>
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<para>Xen via libvirt is currently only supported with nova networking. A number of bugs
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are currently worked on to make sure that Xen via libvirt will also work with Neutron.</para>
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</listitem>
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</itemizedlist>
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</section>
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<section xml:id="xen-libvirt-additional-information">
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<title>Additional information and resources</title>
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<para>The following section contains links to other useful resources</para>
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<itemizedlist>
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<listitem>
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<para><link
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xlink:href="http://wiki.xenproject.org/wiki/OpenStack"
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>wiki.xenproject.org/wiki/OpenStack</link> - OpenStack Documentation on the Xen Project wiki</para>
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</listitem>
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<listitem>
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<para><link
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xlink:href="http://wiki.xenproject.org/wiki/OpenStack_CI_Loop_for_Xen-Libvirt"
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>wiki.xenproject.org/wiki/OpenStack_CI_Loop_for_Xen-Libvirt</link> - Information about the
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Xen Project OpenStack CI Loop</para>
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</listitem>
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<listitem>
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<para><link
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xlink:href="http://wiki.xenproject.org/wiki/OpenStack_via_DevStack"
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>wiki.xenproject.org/wiki/OpenStack_via_DevStack</link> - How to set up OpenStack via DevStack</para>
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</listitem>
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<listitem>
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<para><link
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xlink:href="http://lists.xenproject.org/cgi-bin/mailman/listinfo/wg-openstack"
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>Mailing lists for OpenStack related issues and questions</link> - This list is dedicated
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to coordinating bug fixes and issues across Xen, libvirt and OpenStack and the CI loop.</para>
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</listitem>
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</itemizedlist>
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</section>
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</section>
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