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322 lines
11 KiB
HTML
322 lines
11 KiB
HTML
<html>
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<body>
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<h1>Xen hypervisor driver</h1>
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<ul id="toc"></ul>
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<p>
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The libvirt Xen driver provides the ability to manage virtual machines
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on any Xen release from 3.0.1 onwards.
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</p>
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<h2><a name="prereq">Deployment pre-requisites</a></h2>
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<p>
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The libvirt Xen driver uses a combination of channels to manage Xen
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virtual machines.
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</p>
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<ul>
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<li>
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<strong>XenD</strong>: Access to the Xen daemon is a mandatory
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requirement for the libvirt Xen driver. It requires that the UNIX
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socket interface be enabled in the <code>/etc/xen/xend-config.sxp</code>
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configuration file. Specifically the config settings
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<code>(xend-unix-server yes)</code>. This path is usually restricted
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to only allow the <code>root</code> user access. As an alternative,
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the HTTP interface can be used, however, this has significant security
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implications.
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</li>
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<li>
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<strong>XenStoreD</strong>: Access to the Xenstore daemon enables
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more efficient codepaths for looking up domain information which
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lowers the CPU overhead of management.
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</li>
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<li>
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<strong>Hypercalls</strong>: The ability to make direct hypercalls
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allows the most efficient codepaths in the driver to be used for
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monitoring domain status.
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</li>
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<li>
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<strong>XM config</strong>: When using Xen releases prior to 3.0.4,
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there is no inactive domain management in XenD. For such releases,
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libvirt will automatically process XM configuration files kept in
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the <code>/etc/xen</code> directory. It is important not to place
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any other non-config files in this directory.
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</li>
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</ul>
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<h2><a name="uri">Connections to Xen driver</a></h2>
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<p>
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The libvirt Xen driver is a single-instance privileged driver,
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with a driver name of 'xen'. Some example conection URIs for
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the libvirt driver are:
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</p>
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<pre>
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xen:/// (local access, direct)
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xen+unix:/// (local access, via daemon)
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xen://example.com/ (remote access, TLS/x509)
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xen+tcp://example.com/ (remote access, SASl/Kerberos)
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xen+ssh://root@example.com/ (remote access, SSH tunnelled)
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</pre>
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<h2><a name="imex">Import and export of libvirt domain XML configs</a></h2>
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<p>The Xen driver currently supports two native
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config formats. The first known as <code>xen-xm</code> is the format
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used by the XM tool for files in <code>/etc/xen</code>. The second
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known as <code>xen-sxpr</code>, is the format used for interacting
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with the XenD's legacy HTTP RPC service.</p>
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<h3><a name="xmlimport">Converting from XM config files to domain XML</a></h3>
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<p>
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The <code>virsh domxml-from-native</code> provides a way to convert an
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existing set of XM config files into a guest description using libvirt Domain XML
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that can then be used by libvirt.
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</p>
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<pre>$ virsh -c xen:/// domxml-from-native xen-xm rhel5.cfg
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<domain type='xen'>
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<name>rhel5pv</name>
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<uuid>8f07fe28-753f-2729-d76d-bdbd892f949a</uuid>
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<memory>2560000</memory>
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<currentMemory>307200</currentMemory>
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<vcpu>4</vcpu>
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<bootloader>/usr/bin/pygrub</bootloader>
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<os>
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<type arch='x86_64' machine='xenpv'>linux</type>
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</os>
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<clock offset='utc'/>
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<on_poweroff>destroy</on_poweroff>
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<on_reboot>restart</on_reboot>
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<on_crash>restart</on_crash>
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<devices>
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<disk type='file' device='disk'>
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<driver name='tap' type='aio'/>
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<source file='/var/lib/xen/images/rhel5pv.img'/>
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<target dev='xvda' bus='xen'/>
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</disk>
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<disk type='file' device='disk'>
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<driver name='tap' type='qcow'/>
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<source file='/root/qcow1-xen.img'/>
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<target dev='xvdd' bus='xen'/>
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</disk>
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<interface type='bridge'>
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<mac address='00:16:3e:60:36:ba'/>
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<source bridge='xenbr0'/>
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</interface>
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<console type='pty'>
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<target port='0'/>
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</console>
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<input type='mouse' bus='xen'/>
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<graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0'/>
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</devices>
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</domain></pre>
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<h3><a name="xmlexport">Converting from domain XML to XM config files</a></h3>
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<p>
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The <code>virsh domxml-to-native</code> provides a way to convert a
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guest description using libvirt Domain XML, into the XM config file
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format.
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</p>
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<pre>$ virsh -c xen:/// domxml-to-native xen-xm rhel5pv.xml
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name = "rhel5pv"
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uuid = "8f07fe28-753f-2729-d76d-bdbd892f949a"
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maxmem = 2500
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memory = 300
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vcpus = 4
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bootloader = "/usr/bin/pygrub"
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kernel = "/var/lib/xen/boot_kernel.0YK-cS"
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ramdisk = "/var/lib/xen/boot_ramdisk.vWgrxK"
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extra = "ro root=/dev/VolGroup00/LogVol00 rhgb quiet"
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on_poweroff = "destroy"
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on_reboot = "restart"
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on_crash = "restart"
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sdl = 0
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vnc = 1
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vncunused = 1
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vnclisten = "0.0.0.0"
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disk = [ "tap:aio:/var/lib/xen/images/rhel5pv.img,xvda,w", "tap:qcow:/root/qcow1-xen.img,xvdd,w" ]
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vif = [ "mac=00:16:3e:60:36:ba,bridge=virbr0,script=vif-bridge,vifname=vif5.0" ]</pre>
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<h2><a name="xmlconfig">Example domain XML config</a></h2>
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<p>
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Below are some example XML configurations for Xen guest domains.
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For full details of the available options, consult the <a href="formatdomain.html">domain XML format</a>
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guide.
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</p>
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<h3>Paravirtualized guest bootloader</h3>
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<p>
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Using a bootloader allows a paravirtualized guest to be booted using
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a kernel stored inside its virtual disk image
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</p>
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<pre><domain type='xen' >
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<name>fc8</name>
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<bootloader>/usr/bin/pygrub</bootloader>
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<os>
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<type>linux</type>
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</os>
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<memory>131072</memory>
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<vcpu>1</vcpu>
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<devices>
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<disk type='file'>
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<source file='/var/lib/xen/images/fc4.img'/>
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<target dev='sda1'/>
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</disk>
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<interface type='bridge'>
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<source bridge='xenbr0'/>
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<mac address='aa:00:00:00:00:11'/>
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<script path='/etc/xen/scripts/vif-bridge'/>
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</interface>
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<console tty='/dev/pts/5'/>
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</devices>
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</domain></pre>
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<h3>Paravirtualized guest direct kernel boot</h3>
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<p>
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For installation of paravirtualized guests it is typical to boot the
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domain using a kernel and initrd stored in the host OS
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</p>
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<pre><domain type='xen' >
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<name>fc8</name>
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<os>
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<type>linux</type>
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<kernel>/var/lib/xen/install/vmlinuz-fedora8-x86_64</kernel>
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<initrd>/var/lib/xen/install/initrd-vmlinuz-fedora8-x86_64</initrd>
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<cmdline> kickstart=http://example.com/myguest.ks </cmdline>
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</os>
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<memory>131072</memory>
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<vcpu>1</vcpu>
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<devices>
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<disk type='file'>
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<source file='/var/lib/xen/images/fc4.img'/>
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<target dev='sda1'/>
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</disk>
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<interface type='bridge'>
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<source bridge='xenbr0'/>
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<mac address='aa:00:00:00:00:11'/>
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<script path='/etc/xen/scripts/vif-bridge'/>
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</interface>
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<graphics type='vnc' port='-1'/>
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<console tty='/dev/pts/5'/>
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</devices>
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</domain></pre>
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<h3>Fullyvirtualized guest BIOS boot</h3>
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<p>
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Fullyvirtualized guests use the emulated BIOS to boot off the primary
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harddisk, CDROM or Network PXE ROM.
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</p>
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<pre><domain type='xen' id='3'>
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<name>fv0</name>
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<uuid>4dea22b31d52d8f32516782e98ab3fa0</uuid>
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<os>
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<type>hvm</type>
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<loader>/usr/lib/xen/boot/hvmloader</loader>
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<boot dev='hd'/>
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</os>
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<memory>524288</memory>
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<vcpu>1</vcpu>
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<on_poweroff>destroy</on_poweroff>
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<on_reboot>restart</on_reboot>
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<on_crash>restart</on_crash>
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<features>
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<pae/>
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<acpi/>
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<apic/>
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</features>
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<clock sync="localtime"/>
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<devices>
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<emulator>/usr/lib/xen/bin/qemu-dm</emulator>
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<interface type='bridge'>
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<source bridge='xenbr0'/>
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<mac address='00:16:3e:5d:c7:9e'/>
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<script path='vif-bridge'/>
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</interface>
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<disk type='file'>
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<source file='/var/lib/xen/images/fv0'/>
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<target dev='hda'/>
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</disk>
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<disk type='file' device='cdrom'>
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<source file='/var/lib/xen/images/fc5-x86_64-boot.iso'/>
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<target dev='hdc'/>
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<readonly/>
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</disk>
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<disk type='file' device='floppy'>
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<source file='/root/fd.img'/>
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<target dev='fda'/>
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</disk>
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<graphics type='vnc' port='5904'/>
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</devices>
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</domain></pre>
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<h3>Fullyvirtualized guest direct kernel boot</h3>
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<p>
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With Xen 3.2.0 or later it is possible to bypass the BIOS and directly
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boot a Linux kernel and initrd as a fullyvirtualized domain. This allows
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for complete automation of OS installation, for example using the Anaconda
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kickstart support.
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</p>
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<pre><domain type='xen' id='3'>
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<name>fv0</name>
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<uuid>4dea22b31d52d8f32516782e98ab3fa0</uuid>
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<os>
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<type>hvm</type>
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<loader>/usr/lib/xen/boot/hvmloader</loader>
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<kernel>/var/lib/xen/install/vmlinuz-fedora8-x86_64</kernel>
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<initrd>/var/lib/xen/install/initrd-vmlinuz-fedora8-x86_64</initrd>
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<cmdline> kickstart=http://example.com/myguest.ks </cmdline>
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</os>
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<memory>524288</memory>
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<vcpu>1</vcpu>
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<on_poweroff>destroy</on_poweroff>
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<on_reboot>restart</on_reboot>
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<on_crash>restart</on_crash>
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<features>
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<pae/>
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<acpi/>
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<apic/>
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</features>
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<clock sync="localtime"/>
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<devices>
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<emulator>/usr/lib/xen/bin/qemu-dm</emulator>
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<interface type='bridge'>
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<source bridge='xenbr0'/>
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<mac address='00:16:3e:5d:c7:9e'/>
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<script path='vif-bridge'/>
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</interface>
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<disk type='file'>
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<source file='/var/lib/xen/images/fv0'/>
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<target dev='hda'/>
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</disk>
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<disk type='file' device='cdrom'>
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<source file='/var/lib/xen/images/fc5-x86_64-boot.iso'/>
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<target dev='hdc'/>
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<readonly/>
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</disk>
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<disk type='file' device='floppy'>
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<source file='/root/fd.img'/>
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<target dev='fda'/>
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</disk>
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<graphics type='vnc' port='5904'/>
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</devices>
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</domain></pre>
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</body>
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</html>
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