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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-source drbd8-utils
m-a update
m-a a-i drbd8
echo drbd minor_count=128 >> /etc/modules
depmod -a
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: <BROADCAST,MULTICAST,UP,10000> 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. Please note that the hostname used
for this must resolve to an IP address reserved exclusively
for this purpose.
</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>