Forward-port: patch 4/4 extended HVM features for 1.2

[ganeti-local] / doc / install.sgml

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  <article class="specification">
  <articleinfo>
    <title>Ganeti installation tutorial</title>
  </articleinfo>
  <para>Documents Ganeti version 1.2</para>

  <sect1>
    <title>Introduction</title>

    <para>
      Ganeti is a cluster virtualization management system based on
      Xen. This document explains how to bootstrap a Ganeti node (Xen
      <literal>dom0</literal>), create a running cluster and install
      virtual instance (Xen <literal>domU</literal>).  You need to
      repeat most of the steps in this document for every node you
      want to install, but of course we recommend creating some
      semi-automatic procedure if you plan to deploy Ganeti on a
      medium/large scale.
    </para>

    <para>
      A basic Ganeti terminology glossary is provided in the
      introductory section of the <emphasis>Ganeti administrator's
      guide</emphasis>. Please refer to that document if you are
      uncertain about the terms we are using.
    </para>

    <para>
      Ganeti has been developed for Linux and is
      distribution-agnostic.  This documentation will use Debian Etch
      as an example system but the examples can easily be translated
      to any other distribution.  You are expected to be familiar with
      your distribution, its package management system, and Xen before
      trying to use Ganeti.
    </para>

    <para>This document is divided into two main sections:

      <itemizedlist>
        <listitem>
          <simpara>Installation of the base system and base
            components</simpara>
        </listitem>
        <listitem>
          <simpara>Configuration of the environment for
            Ganeti</simpara>
        </listitem>
      </itemizedlist>

      Each of these is divided into sub-sections. While a full Ganeti system
      will need all of the steps specified, some are not strictly required for
      every environment. Which ones they are, and why, is specified in the
      corresponding sections.
    </para>

  </sect1>

  <sect1>
    <title>Installing the base system and base components</title>

    <sect2>
      <title>Hardware requirements</title>

      <para>
        Any system supported by your Linux distribution is fine.  64-bit
        systems are better as they can support more memory.
      </para>

      <para>
        Any disk drive recognized by Linux
        (<literal>IDE</literal>/<literal>SCSI</literal>/<literal>SATA</literal>/etc.)
        is supported in Ganeti. Note that no shared storage (e.g.
        <literal>SAN</literal>) is needed to get high-availability features. It
        is highly recommended to use more than one disk drive to improve speed.
        But Ganeti also works with one disk per machine.
      </para>

    <sect2>
      <title>Installing the base system</title>

      <para>
        <emphasis role="strong">Mandatory</emphasis> on all nodes.
      </para>

      <para>
        It is advised to start with a clean, minimal install of the
        operating system. The only requirement you need to be aware of
        at this stage is to partition leaving enough space for a big
        (<emphasis role="strong">minimum
        <constant>20GiB</constant></emphasis>) LVM volume group which
        will then host your instance filesystems. The volume group
        name Ganeti 1.2 uses (by default) is
        <emphasis>xenvg</emphasis>.
      </para>

      <para>
        While you can use an existing system, please note that the
        Ganeti installation is intrusive in terms of changes to the
        system configuration, and it's best to use a newly-installed
        system without important data on it.
      </para>

      <para>
        Also, for best results, it's advised that the nodes have as
        much as possible the same hardware and software
        configuration. This will make administration much easier.
      </para>

      <sect3>
        <title>Hostname issues</title>
        <para>
          Note that Ganeti requires the hostnames of the systems
          (i.e. what the <computeroutput>hostname</computeroutput>
          command outputs to be a fully-qualified name, not a short
          name. In other words, you should use
          <literal>node1.example.com</literal> as a hostname and not
          just <literal>node1</literal>.
        </para>

        <formalpara>
          <title>Debian</title>
          <para>
            Note that Debian Etch configures the hostname differently
            than you need it for Ganeti. For example, this is what
            Etch puts in <filename>/etc/hosts</filename> in certain
            situations:
<screen>
127.0.0.1       localhost
127.0.1.1       node1.example.com node1
</screen>

          but for Ganeti you need to have:
<screen>
127.0.0.1       localhost
192.168.1.1     node1.example.com node1
</screen>
            replacing <literal>192.168.1.1</literal> with your node's
            address. Also, the file <filename>/etc/hostname</filename>
            which configures the hostname of the system should contain
            <literal>node1.example.com</literal> and not just
            <literal>node1</literal> (you need to run the command
            <computeroutput>/etc/init.d/hostname.sh
            start</computeroutput> after changing the file).
          </para>
        </formalpara>
      </sect3>

    </sect2>

    <sect2>
      <title>Installing Xen</title>

      <para>
        <emphasis role="strong">Mandatory</emphasis> on all nodes.
      </para>

      <para>
        While Ganeti is developed with the ability to modularly run on
        different virtualization environments in mind the only one
        currently useable on a live system is <ulink
        url="http://xen.xensource.com/">Xen</ulink>. Supported
        versions are: <simplelist type="inline">
        <member><literal>3.0.3</literal></member>
        <member><literal>3.0.4</literal></member>
        <member><literal>3.1</literal></member> </simplelist>.
      </para>

      <para>
        Please follow your distribution's recommended way to install
        and set up Xen, or install Xen from the upstream source, if
        you wish, following their manual.
      </para>

      <para>
        After installing Xen you need to reboot into your Xen-ified
        dom0 system. On some distributions this might involve
        configuring GRUB appropriately, whereas others will configure
        it automatically when you install Xen from a package.
      </para>

      <formalpara><title>Debian</title>
      <para>
        Under Debian Etch or Sarge+backports you can install the
        relevant <literal>xen-linux-system</literal> package, which
        will pull in both the hypervisor and the relevant
        kernel. Also, if you are installing a 32-bit Etch, you should
        install the <computeroutput>libc6-xen</computeroutput> package
        (run <computeroutput>apt-get install
        libc6-xen</computeroutput>).
      </para>
      </formalpara>

      <sect3>
        <title>Xen settings</title>

        <para>
          It's recommended that dom0 is restricted to a low amount of
          memory (<constant>512MiB</constant> is reasonable) and that
          memory ballooning is disabled in the file
          <filename>/etc/xen/xend-config.sxp</filename> by setting the
          value <literal>dom0-min-mem</literal> to
          <constant>0</constant>, like this:
          <computeroutput>(dom0-min-mem 0)</computeroutput>
        </para>

        <para>
          For optimum performance when running both CPU and I/O
          intensive instances, it's also recommended that the dom0 is
          restricted to one CPU only, for example by booting with the
          kernel parameter <literal>nosmp</literal>.
        </para>

        <para>
          It is recommended that you disable xen's automatic save of virtual
          machines at system shutdown and subsequent restore of them at reboot.
          To obtain this make sure the variable
          <literal>XENDOMAINS_SAVE</literal> in the file
          <literal>/etc/default/xendomains</literal> is set to an empty value.
        </para>

        <formalpara>
          <title>Debian</title>
          <para>
            Besides the ballooning change which you need to set in
            <filename>/etc/xen/xend-config.sxp</filename>, you need to
            set the memory and nosmp parameters in the file
            <filename>/boot/grub/menu.lst</filename>. You need to
            modify the variable <literal>xenhopt</literal> to add
            <userinput>dom0_mem=512M</userinput> like this:
<screen>
## Xen hypervisor options to use with the default Xen boot option
# xenhopt=dom0_mem=512M
</screen>
            and the <literal>xenkopt</literal> needs to include the
            <userinput>nosmp</userinput> option like this:
<screen>
## Xen Linux kernel options to use with the default Xen boot option
# xenkopt=nosmp
</screen>

          Any existing parameters can be left in place: it's ok to
          have <computeroutput>xenkopt=console=tty0
          nosmp</computeroutput>, for example. After modifying the
          files, you need to run:
<screen>
/sbin/update-grub
</screen>
          </para>
        </formalpara>
        <para>
          If you want to test the HVM support
          with Ganeti and want VNC access to the console of your
          instances, set the following two entries in
          <filename>/etc/xen/xend-config.sxp</filename>:
<screen>
(vnc-listen '0.0.0.0')
(vncpasswd '')
</screen>
          You need to restart the Xen daemon for these settings to
          take effect:
<screen>
/etc/init.d/xend restart
</screen>
        </para>

      </sect3>

      <sect3>
        <title>Selecting the instance kernel</title>

        <para>
          After you have installed Xen, you need to tell Ganeti
          exactly what kernel to use for the instances it will
          create. This is done by creating a
          <emphasis>symlink</emphasis> from your actual kernel to
          <filename>/boot/vmlinuz-2.6-xenU</filename>, and one from
          your initrd to
          <filename>/boot/initrd-2.6-xenU</filename>. Note that if you
          don't use an initrd for the <literal>domU</literal> kernel,
          you don't need to create the initrd symlink.
        </para>

        <formalpara>
          <title>Debian</title>
          <para>
            After installation of the
            <literal>xen-linux-system</literal> package, you need to
            run (replace the exact version number with the one you
            have):
            <screen>
cd /boot
ln -s vmlinuz-2.6.18-5-xen-686 vmlinuz-2.6-xenU
ln -s initrd.img-2.6.18-5-xen-686 initrd-2.6-xenU
            </screen>
          </para>
        </formalpara>
      </sect3>

    </sect2>

    <sect2>
      <title>Installing DRBD</title>

      <para>
        Recommended on all nodes: <ulink
        url="http://www.drbd.org/">DRBD</ulink> is required if you
        want to use the high availability (HA) features of Ganeti, but
        optional if you don't require HA or only run Ganeti on
        single-node clusters. You can upgrade a non-HA cluster to an
        HA one later, but you might need to export and re-import all
        your instances to take advantage of the new features.
      </para>

      <para>
        Supported DRBD versions: <literal>8.0.x</literal>.
        It's recommended to have at least version <literal>8.0.7</literal>.
      </para>

      <para>
        Now the bad news: unless your distribution already provides it
        installing DRBD might involve recompiling your kernel or
        anyway fiddling with it. Hopefully at least the Xen-ified
        kernel source to start from will be provided.
      </para>

      <para>
        The good news is that you don't need to configure DRBD at all.
        Ganeti will do it for you for every instance you set up.  If
        you have the DRBD utils installed and the module in your
        kernel you're fine. Please check that your system is
        configured to load the module at every boot, and that it
        passes the following option to the module
        <computeroutput>minor_count=255</computeroutput>. This will
        allow you to use up to 128 instances per node (for most clusters
        <constant>128 </constant> should be enough, though).
      </para>

      <formalpara><title>Debian</title>
        <para>
         You can just install (build) the DRBD 8.0.x module with the
         following commands (make sure you are running the Xen
         kernel):
        </para>
      </formalpara>

      <screen>
apt-get install -t etch-backports drbd8-module-source drbd8-utils
m-a update
m-a a-i drbd8
echo drbd minor_count=128 >> /etc/modules
modprobe drbd minor_count=128
      </screen>

      <para>
        It is also recommended that you comment out the default
        resources in the <filename>/etc/drbd.conf</filename> file, so
        that the init script doesn't try to configure any drbd
        devices. You can do this by prefixing all
        <literal>resource</literal> lines in the file with the keyword
        <literal>skip</literal>, like this:
      </para>

      <screen>
skip resource r0 {
...
}

skip resource "r1" {
...
}
      </screen>

    </sect2>

    <sect2>
      <title>Other required software</title>

      <para>Besides Xen and DRBD, you will need to install the
      following (on all nodes):</para>

      <itemizedlist>
        <listitem>
          <simpara><ulink url="http://sourceware.org/lvm2/">LVM
          version 2</ulink></simpara>
        </listitem>
        <listitem>
          <simpara><ulink
          url="http://www.openssl.org/">OpenSSL</ulink></simpara>
        </listitem>
        <listitem>
          <simpara><ulink
          url="http://www.openssh.com/portable.html">OpenSSH</ulink></simpara>
        </listitem>
        <listitem>
          <simpara><ulink url="http://bridge.sourceforge.net/">Bridge
          utilities</ulink></simpara>
        </listitem>
        <listitem>
          <simpara><ulink
          url="http://developer.osdl.org/dev/iproute2">iproute2</ulink></simpara>
        </listitem>
        <listitem>
          <simpara><ulink
          url="ftp://ftp.inr.ac.ru/ip-routing/iputils-current.tar.gz">arping</ulink>
          (part of iputils package)</simpara>
        </listitem>
        <listitem>
          <simpara><ulink url="http://www.python.org">Python 2.4</ulink></simpara>
        </listitem>
        <listitem>
          <simpara><ulink
          url="http://pyopenssl.sourceforge.net/">Python OpenSSL
          bindings</ulink></simpara>
        </listitem>
        <listitem>
          <simpara><ulink
          url="http://www.undefined.org/python/#simplejson">simplejson Python
          module</ulink></simpara>
        </listitem>
        <listitem>
          <simpara><ulink
          url="http://pyparsing.wikispaces.com/">pyparsing Python
          module</ulink></simpara>
        </listitem>
      </itemizedlist>

      <para>
        These programs are supplied as part of most Linux
        distributions, so usually they can be installed via apt or
        similar methods. Also many of them will already be installed
        on a standard machine.
      </para>


      <formalpara><title>Debian</title>

      <para>You can use this command line to install all of them:</para>

      </formalpara>
      <screen>
# apt-get install lvm2 ssh bridge-utils iproute iputils-arping \
  python2.4 python-pyopenssl openssl python-pyparsing python-simplejson
      </screen>

    </sect2>

  </sect1>


  <sect1>
    <title>Setting up the environment for Ganeti</title>

    <sect2>
      <title>Configuring the network</title>

      <para><emphasis role="strong">Mandatory</emphasis> on all nodes.</para>

      <para>
        Ganeti relies on Xen running in "bridge mode", which means the
        instances network interfaces will be attached to a software bridge
        running in dom0. Xen by default creates such a bridge at startup, but
        your distribution might have a different way to do things.
      </para>

      <para>
        Beware that the default name Ganeti uses is
        <hardware>xen-br0</hardware> (which was used in Xen 2.0)
        while Xen 3.0 uses <hardware>xenbr0</hardware> by
        default. The default bridge your Ganeti cluster will use for new
        instances can be specified at cluster initialization time.
      </para>

      <formalpara><title>Debian</title>
        <para>
          The recommended Debian way to configure the Xen bridge is to
          edit your <filename>/etc/network/interfaces</filename> file
          and substitute your normal Ethernet stanza with the
          following snippet:

        <screen>
auto xen-br0
iface xen-br0 inet static
        address <replaceable>YOUR_IP_ADDRESS</replaceable>
        netmask <replaceable>YOUR_NETMASK</replaceable>
        network <replaceable>YOUR_NETWORK</replaceable>
        broadcast <replaceable>YOUR_BROADCAST_ADDRESS</replaceable>
        gateway <replaceable>YOUR_GATEWAY</replaceable>
        bridge_ports eth0
        bridge_stp off
        bridge_fd 0
        </screen>
        </para>
      </formalpara>

     <para>
The following commands need to be executed on the local console
     </para>
      <screen>
ifdown eth0
ifup xen-br0
      </screen>

      <para>
        To check if the bridge is setup, use <command>ip</command>
        and <command>brctl show</command>:
      <para>

      <screen>
# ip a show xen-br0
9: xen-br0: &lt;BROADCAST,MULTICAST,UP,10000&gt; mtu 1500 qdisc noqueue
    link/ether 00:20:fc:1e:d5:5d brd ff:ff:ff:ff:ff:ff
    inet 10.1.1.200/24 brd 10.1.1.255 scope global xen-br0
    inet6 fe80::220:fcff:fe1e:d55d/64 scope link
       valid_lft forever preferred_lft forever

# brctl show xen-br0
bridge name     bridge id               STP enabled     interfaces
xen-br0         8000.0020fc1ed55d       no              eth0
      </screen>


    </sect2>

    <sect2>
      <title>Configuring LVM</title>


      <para><emphasis role="strong">Mandatory</emphasis> on all nodes.</para>

      <note>
        <simpara>The volume group is required to be at least
        <constant>20GiB</constant>.</simpara>
      </note>
      <para>
        If you haven't configured your LVM volume group at install
        time you need to do it before trying to initialize the Ganeti
        cluster. This is done by formatting the devices/partitions you
        want to use for it and then adding them to the relevant volume
        group:

       <screen>
pvcreate /dev/sda3
vgcreate xenvg /dev/sda3
       </screen>
or
       <screen>
pvcreate /dev/sdb1
pvcreate /dev/sdc1
vgcreate xenvg /dev/sdb1 /dev/sdc1
       </screen>
      </para>

      <para>
        If you want to add a device later you can do so with the
        <citerefentry><refentrytitle>vgextend</refentrytitle>
        <manvolnum>8</manvolnum></citerefentry> command:
      </para>

      <screen>
pvcreate /dev/sdd1
vgextend xenvg /dev/sdd1
      </screen>

      <formalpara>
        <title>Optional</title>
        <para>
          It is recommended to configure LVM not to scan the DRBD
          devices for physical volumes. This can be accomplished by
          editing <filename>/etc/lvm/lvm.conf</filename> and adding
          the <literal>/dev/drbd[0-9]+</literal> regular expression to
          the <literal>filter</literal> variable, like this:
<screen>
    filter = [ "r|/dev/cdrom|", "r|/dev/drbd[0-9]+|" ]
</screen>
        </para>
      </formalpara>

    </sect2>

    <sect2>
      <title>Installing Ganeti</title>

      <para><emphasis role="strong">Mandatory</emphasis> on all nodes.</para>

      <para>
        It's now time to install the Ganeti software itself.  Download
        the source from <ulink
        url="http://code.google.com/p/ganeti/"></ulink>.
      </para>

        <screen>
tar xvzf ganeti-@GANETI_VERSION@.tar.gz
cd ganeti-@GANETI_VERSION@
./configure --localstatedir=/var --sysconfdir=/etc
make
make install
mkdir /srv/ganeti/ /srv/ganeti/os /srv/ganeti/export
        </screen>

      <para>
        You also need to copy the file
        <filename>doc/examples/ganeti.initd</filename>
        from the source archive to
        <filename>/etc/init.d/ganeti</filename> and register it with
        your distribution's startup scripts, for example in Debian:
      </para>
      <screen>update-rc.d ganeti defaults 20 80</screen>

      <para>
        In order to automatically restart failed instances, you need
        to setup a cron job run the
        <computeroutput>ganeti-watcher</computeroutput> program. A
        sample cron file is provided in the source at
        <filename>doc/examples/ganeti.cron</filename> and you can
        copy that (eventually altering the path) to
        <filename>/etc/cron.d/ganeti</filename>
      </para>

    </sect2>

    <sect2>
      <title>Installing the Operating System support packages</title>

      <para><emphasis role="strong">Mandatory</emphasis> on all nodes.</para>

      <para>
        To be able to install instances you need to have an Operating
        System installation script. An example for Debian Etch is
        provided on the project web site.  Download it from <ulink
        url="http://code.google.com/p/ganeti/"></ulink> and follow the
        instructions in the <filename>README</filename> file.  Here is
        the installation procedure (replace <constant>0.2</constant>
        with the latest version that is compatible with your ganeti
        version):
      </para>

      <screen>
cd /srv/ganeti/os
tar xvf ganeti-instance-debian-etch-0.4.tar
mv ganeti-instance-debian-etch-0.4 debian-etch
      </screen>

      <para>
        In order to use this OS definition, you need to have internet
        access from your nodes and have the <citerefentry>
        <refentrytitle>debootstrap</refentrytitle>
        <manvolnum>8</manvolnum></citerefentry>, <citerefentry>
        <refentrytitle>dump</refentrytitle><manvolnum>8</manvolnum>
        </citerefentry> and <citerefentry>
        <refentrytitle>restore</refentrytitle>
        <manvolnum>8</manvolnum> </citerefentry> commands installed on
        all nodes.
      </para>
      <formalpara>
        <title>Debian</title>
        <para>
          Use this command on all nodes to install the required
          packages:

          <screen>apt-get install debootstrap dump</screen>
        </para>
      </formalpara>

      <para>
        Alternatively, you can create your own OS definitions. See the
        manpage
        <citerefentry>
        <refentrytitle>ganeti-os-interface</refentrytitle>
        <manvolnum>8</manvolnum>
        </citerefentry>.
      </para>

    </sect2>

    <sect2>
      <title>Initializing the cluster</title>

      <para><emphasis role="strong">Mandatory:</emphasis> only on one
      node per cluster.</para>


      <para>The last step is to initialize the cluster. After you've repeated
        the above process on all of your nodes, choose one as the master, and execute:
      </para>

      <screen>
gnt-cluster init <replaceable>CLUSTERNAME</replaceable>
      </screen>

      <para>
        The <replaceable>CLUSTERNAME</replaceable> is a hostname,
        which must be resolvable (e.g. it must exist in DNS or in
        <filename>/etc/hosts</filename>) by all the nodes in the
        cluster. You must choose a name different from any of the
        nodes names for a multi-node cluster. In general the best
        choice is to have a unique name for a cluster, even if it
        consists of only one machine, as you will be able to expand it
        later without any problems.
      </para>

      <para>
        If the bridge name you are using is not
        <literal>xen-br0</literal>, use the <option>-b
        <replaceable>BRIDGENAME</replaceable></option> option to
        specify the bridge name. In this case, you should also use the
        <option>--master-netdev
        <replaceable>BRIDGENAME</replaceable></option> option with the
        same <replaceable>BRIDGENAME</replaceable> argument.
      </para>

      <para>
        You can use a different name than <literal>xenvg</literal> for
        the volume group (but note that the name must be identical on
        all nodes). In this case you need to specify it by passing the
        <option>-g <replaceable>VGNAME</replaceable></option> option
        to <computeroutput>gnt-cluster init</computeroutput>.
      </para>

      <para>
        To set up the cluster as an HVM cluster, use the
        <option>--hypervisor=xen-hvm3.1</option> option to use
        the Xen 3.1 HVM hypervisor. Note that with the
        HVM support, you will only be able to create
        HVM instances in a cluster set to this hypervisor type. Mixed
        PVM/HVM clusters are not supported by the Ganeti 1.2
        HVM support. You will also need to create the VNC
        cluster password  file
        <filename>/etc/ganeti/vnc-cluster-password</filename>
        which contains one line with the default VNC password for the
        cluster.
      </para>

      <para>
        You can also invoke the command with the
        <option>--help</option> option in order to see all the
        possibilities.
      </para>

    </sect2>

    <sect2>
      <title>Joining the nodes to the cluster</title>

      <para>
        <emphasis role="strong">Mandatory:</emphasis> for all the
        other nodes.
      </para>

      <para>
        After you have initialized your cluster you need to join the
        other nodes to it. You can do so by executing the following
        command on the master node:
      </para>
        <screen>
gnt-node add <replaceable>NODENAME</replaceable>
        </screen>
    </sect2>

    <sect2>
      <title>Separate replication network</title>

      <para><emphasis role="strong">Optional</emphasis></para>
      <para>
        Ganeti uses DRBD to mirror the disk of the virtual instances
        between nodes. To use a dedicated network interface for this
        (in order to improve performance or to enhance security) you
        need to configure an additional interface for each node.  Use
        the <option>-s</option> option with
        <computeroutput>gnt-cluster init</computeroutput> and
        <computeroutput>gnt-node add</computeroutput> to specify the
        IP address of this secondary interface to use for each
        node. Note that if you specified this option at cluster setup
        time, you must afterwards use it for every node add operation.
      </para>
    </sect2>

    <sect2>
      <title>Testing the setup</title>

      <para>
        Execute the <computeroutput>gnt-node list</computeroutput>
        command to see all nodes in the cluster:
      <screen>
# gnt-node list
Node              DTotal  DFree MTotal MNode MFree Pinst Sinst
node1.example.com 197404 197404   2047  1896   125     0     0
      </screen>
    </para>
  </sect2>

  <sect1>
    <title>Setting up and managing virtual instances</title>
    <sect2>
      <title>Setting up virtual instances</title>
      <para>
        This step shows how to setup a virtual instance with either
        non-mirrored disks (<computeroutput>plain</computeroutput>) or
        with network mirrored disks
        (<computeroutput>drbd</computeroutput>).  All
        commands need to be executed on the Ganeti master node (the
        one on which <computeroutput>gnt-cluster init</computeroutput>
        was run).  Verify that the OS scripts are present on all
        cluster nodes with <computeroutput>gnt-os
        list</computeroutput>.
      </para>
      <para>
        To create a virtual instance, you need a hostname which is
        resolvable (DNS or <filename>/etc/hosts</filename> on all
        nodes). The following command will create a non-mirrored
        instance for you:
      </para>
      <screen>
gnt-instance add --node=node1 -o debian-etch -t plain inst1.example.com
* creating instance disks...
adding instance inst1.example.com to cluster config
Waiting for instance inst1.example.com to sync disks.
Instance inst1.example.com's disks are in sync.
creating os for instance inst1.example.com on node node1.example.com
* running the instance OS create scripts...
      </screen>

      <para>
        The above instance will have no network interface enabled.
        You can access it over the virtual console with
        <computeroutput>gnt-instance console
        <literal>inst1</literal></computeroutput>. There is no
        password for root.  As this is a Debian instance, you can
        modify the <filename>/etc/network/interfaces</filename> file
        to setup the network interface (<literal>eth0</literal> is the
        name of the interface provided to the instance).
      </para>

      <para>
        To create a network mirrored instance, change the argument to
        the <option>-t</option> option from <literal>plain</literal>
        to <literal>drbd</literal> and specify the node on
        which the mirror should reside with the second value of the
        <option>--node</option> option, like this:
      </para>

      <screen>
# gnt-instance add -t drbd -n node1:node2 -o debian-etch instance2
* creating instance disks...
adding instance instance2 to cluster config
Waiting for instance instance1 to sync disks.
- device sdb:  3.50% done, 304 estimated seconds remaining
- device sdb: 21.70% done, 270 estimated seconds remaining
- device sdb: 39.80% done, 247 estimated seconds remaining
- device sdb: 58.10% done, 121 estimated seconds remaining
- device sdb: 76.30% done, 72 estimated seconds remaining
- device sdb: 94.80% done, 18 estimated seconds remaining
Instance instance2's disks are in sync.
creating os for instance instance2 on node node1.example.com
* running the instance OS create scripts...
* starting instance...
      </screen>

    </sect2>

    <sect2>
      <title>Managing virtual instances</title>
      <para>
        All commands need to be executed on the Ganeti master node
      </para>

      <para>
        To access the console of an instance, use
        <computeroutput>gnt-instance console
        <replaceable>INSTANCENAME</replaceable></computeroutput>.
      </para>

      <para>
        To shutdown an instance, use <computeroutput>gnt-instance
        shutdown
        <replaceable>INSTANCENAME</replaceable></computeroutput>. To
        startup an instance, use <computeroutput>gnt-instance startup
        <replaceable>INSTANCENAME</replaceable></computeroutput>.
      </para>

      <para>
        To failover an instance to its secondary node (only possible
        with <literal>drbd</literal> disk templates), use
        <computeroutput>gnt-instance failover
        <replaceable>INSTANCENAME</replaceable></computeroutput>.
      </para>

      <para>
        For more instance and cluster administration details, see the
        <emphasis>Ganeti administrator's guide</emphasis>.
      </para>

    </sect2>

  </sect1>

  </article>