Synnefo » snf-ganeti

Ganeti installation tutorial

============================

Documents Ganeti version |version|

.. contents::

Introduction

------------

Ganeti is a cluster virtualization management system based on Xen or

KVM. This document explains how to bootstrap a Ganeti node (Xen

*dom0*), create a running cluster and install virtual instance (Xen

*domU*).  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.

A basic Ganeti terminology glossary is provided in the introductory

section of the *Ganeti administrator's guide*. Please refer to that

document if you are uncertain about the terms we are using.

Ganeti has been developed for Linux and is distribution-agnostic.

This documentation will use Debian Lenny as an example system but the

examples can easily be translated to any other distribution. ou are

expected to be familiar with your distribution, its package management

system, and Xen or KVM before trying to use Ganeti.

This document is divided into two main sections:

- Installation of the base system and base components

- Configuration of the environment for Ganeti

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.

Installing the base system and base components

----------------------------------------------

Hardware requirements

+++++++++++++++++++++

Any system supported by your Linux distribution is fine. 64-bit

systems are better as they can support more memory.

Any disk drive recognized by Linux (``IDE``/``SCSI``/``SATA``/etc.)

is supported in Ganeti. Note that no shared storage (e.g.  ``SAN``) is

needed to get high-availability features (but of course, one can be

used to store the images). It is highly recommended to use more than

one disk drive to improve speed. But Ganeti also works with one disk

per machine.

Installing the base system

++++++++++++++++++++++++++

**Mandatory** on all nodes.

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 (**minimum** 20GiB) LVM

volume group which will then host your instance filesystems, if you

want to use all Ganeti features. The volume group name Ganeti 2.0 uses

(by default) is ``xenvg``.

You can also use file-based storage only, without LVM, but this setup

is not detailed in this document.

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.

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.

Hostname issues

~~~~~~~~~~~~~~~

Note that Ganeti requires the hostnames of the systems (i.e. what the

``hostname`` command outputs to be a fully-qualified name, not a short

name. In other words, you should use *node1.example.com* as a hostname

and not just *node1*.

.. admonition:: Debian

   Debian Lenny and Etch configures the hostname differently than you

   need it for Ganeti. For example, this is what Etch puts in

   ``/etc/hosts`` in certain situations::

     127.0.0.1       localhost

     127.0.1.1       node1.example.com node1

   but for Ganeti you need to have::

     127.0.0.1       localhost

     192.168.1.1     node1.example.com node1

   replacing ``192.168.1.1`` with your node's address. Also, the file

   ``/etc/hostname`` which configures the hostname of the system

   should contain ``node1.example.com`` and not just ``node1`` (you

   need to run the command ``/etc/init.d/hostname.sh start`` after

   changing the file).

.. admonition:: Why a fully qualified host name

   Although most distributions use only the short name in the /etc/hostname

   file, we still think Ganeti nodes should use the full name. The reason for

   this is that calling 'hostname --fqdn' requires the resolver library to work

   and is a 'guess' via heuristics at what is your domain name. Since Ganeti

   can be used among other things to host DNS servers, we don't want to depend

   on them as much as possible, and we'd rather have the uname() syscall return

   the full node name.

   We haven't ever found any breakage in using a full hostname on a Linux

   system, and anyway we recommend to have only a minimal installation on

   Ganeti nodes, and to use instances (or other dedicated machines) to run the

   rest of your network services. By doing this you can change the

   /etc/hostname file to contain an FQDN without the fear of breaking anything

   unrelated.

Installing Xen

++++++++++++++

**Mandatory** on all nodes.

While Ganeti is developed with the ability to modularly run on

different virtualization environments in mind the only two currently

useable on a live system are Xen and KVM. Supported

Xen versions are: 3.0.3, 3.0.4 and 3.1.

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. For KVM, make sure you have a KVM-enabled

kernel and the KVM tools.

After installing either hypervisor, you need to reboot into your new

system. On some distributions this might involve configuring GRUB

appropriately, whereas others will configure it automatically when you

install the respective kernels.

.. admonition:: Debian

   Under Lenny or Etch you can install the relevant

   ``xen-linux-system`` package, which will pull in both the

   hypervisor and the relevant kernel. Also, if you are installing a

   32-bit Lenny/Etch, you should install the ``libc6-xen`` package

   (run ``apt-get install libc6-xen``).

Xen settings

~~~~~~~~~~~~

It's recommended that dom0 is restricted to a low amount of memory

(512MiB or 1GiB is reasonable) and that memory ballooning is disabled

in the file ``/etc/xen/xend-config.sxp`` by setting

the value ``dom0-min-mem`` to 0,

like this::

  (dom0-min-mem 0)

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 ``nosmp``.

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 ``XENDOMAINS_SAVE`` in the file

``/etc/default/xendomains`` is set to an empty value.

.. admonition:: Debian

   Besides the ballooning change which you need to set in

   ``/etc/xen/xend-config.sxp``, you need to set the memory and nosmp

   parameters in the file ``/boot/grub/menu.lst``. You need to modify

   the variable ``xenhopt`` to add ``dom0_mem=1024M`` like this::

     ## Xen hypervisor options to use with the default Xen boot option

     # xenhopt=dom0_mem=1024M

   and the ``xenkopt`` needs to include the ``nosmp`` option like

   this::

     ## Xen Linux kernel options to use with the default Xen boot option

     # xenkopt=nosmp

   Any existing parameters can be left in place: it's ok to have

   ``xenkopt=console=tty0 nosmp``, for example. After modifying the

   files, you need to run::

     /sbin/update-grub

If you want to run HVM instances too with Ganeti and want VNC access

to the console of your instances, set the following two entries in

``/etc/xen/xend-config.sxp``::

  (vnc-listen '0.0.0.0') (vncpasswd '')

You need to restart the Xen daemon for these settings to take effect::

  /etc/init.d/xend restart

Selecting the instance kernel

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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 symlink from your actual kernel to

``/boot/vmlinuz-2.6-xenU``, and one from your initrd

to ``/boot/initrd-2.6-xenU``. Note that if you don't

use an initrd for the domU kernel, you don't need

to create the initrd symlink.

.. admonition:: Debian

   After installation of the ``xen-linux-system`` package, you need to

   run (replace the exact version number with the one you have)::

     cd /boot

     ln -s vmlinuz-2.6.26-1-xen-amd64 vmlinuz-2.6-xenU

     ln -s initrd.img-2.6.26-1-xen-amd64 initrd-2.6-xenU

Installing DRBD

+++++++++++++++

Recommended on all nodes: DRBD_ 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.

.. _DRBD: http://www.drbd.org/

Supported DRBD versions: 8.0.x. It's recommended to have at least

version 8.0.12.

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.

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

``minor_count=255``. This will allow you to use up to 128 instances

per node (for most clusters 128 should be enough, though).

.. admonition:: Debian

   On Debian, you can just install (build) the DRBD 8.0.x module with

   the following commands (make sure you are running the Xen kernel)::

     apt-get install 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

   It is also recommended that you comment out the default resources

   in the ``/etc/drbd.conf`` file, so that the init script doesn't try

   to configure any drbd devices. You can do this by prefixing all

   *resource* lines in the file with the keyword *skip*, like this::

     skip resource r0 {

       ...

     }

     skip resource "r1" {

       ...

     }

Other required software

+++++++++++++++++++++++

Besides Xen and DRBD, you will need to install the following (on all

nodes):

- LVM version 2, `<http://sourceware.org/lvm2/>`_

- OpenSSL, `<http://www.openssl.org/>`_

- OpenSSH, `<http://www.openssh.com/portable.html>`_

- bridge utilities, `<http://bridge.sourceforge.net/>`_

- iproute2, `<http://developer.osdl.org/dev/iproute2>`_

- arping (part of iputils package),

  `<ftp://ftp.inr.ac.ru/ip-routing/iputils-current.tar.gz>`_

- Python version 2.4 or 2.5, `<http://www.python.org>`_

- Python OpenSSL bindings, `<http://pyopenssl.sourceforge.net/>`_

- simplejson Python module, `<http://www.undefined.org/python/#simplejson>`_

- pyparsing Python module, `<http://pyparsing.wikispaces.com/>`_

- pyinotify Python module, `<http://trac.dbzteam.org/pyinotify>`_

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.

.. admonition:: Debian

   You can use this command line to install all needed packages::

     # apt-get install lvm2 ssh bridge-utils iproute iputils-arping \

     python python-pyopenssl openssl python-pyparsing python-simplejson \

     python-pyinotify

Setting up the environment for Ganeti

-------------------------------------

Configuring the network

+++++++++++++++++++++++

**Mandatory** on all nodes.

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.

Beware that the default name Ganeti uses is ``xen-br0`` (which was

used in Xen 2.0) while Xen 3.0 uses ``xenbr0`` by default. The default

bridge your Ganeti cluster will use for new instances can be specified

at cluster initialization time.

.. admonition:: Debian

   The recommended way to configure the Xen bridge is to edit your

   ``/etc/network/interfaces`` file and substitute your normal

   Ethernet stanza with the following snippet::

     auto xen-br0

     iface xen-br0 inet static

        address YOUR_IP_ADDRESS

        netmask YOUR_NETMASK

        network YOUR_NETWORK

        broadcast YOUR_BROADCAST_ADDRESS

        gateway YOUR_GATEWAY

        bridge_ports eth0

        bridge_stp off

        bridge_fd 0

The following commands need to be executed on the local console:

  ifdown eth0

  ifup xen-br0

To check if the bridge is setup, use the ``ip`` and ``brctl show``

commands::

  # 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

Configuring LVM

+++++++++++++++

**Mandatory** on all nodes.

The volume group is required to be at least 20GiB.

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::

  pvcreate /dev/sda3

  vgcreate xenvg /dev/sda3

or::

  pvcreate /dev/sdb1

  pvcreate /dev/sdc1

  vgcreate xenvg /dev/sdb1 /dev/sdc1

If you want to add a device later you can do so with the *vgextend*

command::

  pvcreate /dev/sdd1

  vgextend xenvg /dev/sdd1

Optional: it is recommended to configure LVM not to scan the DRBD

devices for physical volumes. This can be accomplished by editing

``/etc/lvm/lvm.conf`` and adding the

``/dev/drbd[0-9]+`` regular expression to the

``filter`` variable, like this::

  filter = ["r|/dev/cdrom|", "r|/dev/drbd[0-9]+|" ]

Installing Ganeti

+++++++++++++++++

**Mandatory** on all nodes.

It's now time to install the Ganeti software itself.  Download the

source from the project page at `<http://code.google.com/p/ganeti/>`_,

and install it (replace 2.0.0 with the latest version)::

  tar xvzf ganeti-2.0.0.tar.gz

  cd ganeti-2.0.0

  ./configure --localstatedir=/var --sysconfdir=/etc

  make

  make install

  mkdir /srv/ganeti/ /srv/ganeti/os /srv/ganeti/export

You also need to copy the file

``doc/examples/ganeti.initd`` from the source archive

to ``/etc/init.d/ganeti`` and register it with your

distribution's startup scripts, for example in Debian::

  update-rc.d ganeti defaults 20 80

In order to automatically restart failed instances, you need to setup

a cron job run the *ganeti-watcher* command. A sample cron file is

provided in the source at ``doc/examples/ganeti.cron`` and you can

copy that (eventually altering the path) to ``/etc/cron.d/ganeti``.

Installing the Operating System support packages

++++++++++++++++++++++++++++++++++++++++++++++++

**Mandatory** on all nodes.

To be able to install instances you need to have an Operating System

installation script. An example OS that works under Debian and can

install Debian and Ubuntu instace OSes is provided on the project web

site.  Download it from the project page and follow the instructions

in the ``README`` file.  Here is the installation procedure (replace

0.7 with the latest version that is compatible with your ganeti

version)::

  cd /usr/local/src/

  wget http://ganeti.googlecode.com/files/ganeti-instance-debootstrap-0.7.tar.gz

  tar xzf ganeti-instance-debootstrap-0.7.tar.gz

  cd ganeti-instance-debootstrap-0.7

  ./configure

  make

  make install

In order to use this OS definition, you need to have internet access

from your nodes and have the *debootstrap*, *dump* and *restore*

commands installed on all nodes. Also, if the OS is configured to

partition the instance's disk in

``/etc/default/ganeti-instance-debootstrap``, you will need *kpartx*

installed.

.. admonition:: Debian

   Use this command on all nodes to install the required packages::

     apt-get install debootstrap dump kpartx

Alternatively, you can create your own OS definitions. See the manpage

:manpage:`ganeti-os-interface`.

Initializing the cluster

++++++++++++++++++++++++

**Mandatory** on one node per cluster.

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::

  gnt-cluster init <CLUSTERNAME>

The *CLUSTERNAME* is a hostname, which must be resolvable (e.g. it

must exist in DNS or in ``/etc/hosts``) 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, and cannot be the name of the first

(master) node.

If the bridge name you are using is not ``xen-br0``, use the *-b

<BRIDGENAME>* option to specify the bridge name. In this case, you

should also use the *--master-netdev <BRIDGENAME>* option with the

same BRIDGENAME argument.

You can use a different name than ``xenvg`` 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 *-g <VGNAME>* option to

``gnt-cluster init``.

To set up the cluster as an HVM cluster, use the

``--enabled-hypervisors=xen-hvm`` option to enable the HVM hypervisor

(you can also add ``,xen-pvm`` to enable the PVM one too). You will

also need to create the VNC cluster password file

``/etc/ganeti/vnc-cluster-password`` which contains one line with the

default VNC password for the cluster.

To setup the cluster for KVM-only usage (KVM and Xen cannot be mixed),

pass ``--enabled-hypervisors=kvm`` to the init command.

You can also invoke the command with the ``--help`` option in order to

see all the possibilities.

Joining the nodes to the cluster

++++++++++++++++++++++++++++++++

**Mandatory** for all the other nodes.

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::

  gnt-node add <NODENAME>

Separate replication network

++++++++++++++++++++++++++++

**Optional**

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 *-s* option with

``gnt-cluster init`` and ``gnt-node add`` 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.

Testing the setup

+++++++++++++++++

Execute the ``gnt-node list`` command to see all nodes in the

cluster::

  # gnt-node list

  Node              DTotal  DFree MTotal MNode MFree Pinst Sinst

  node1.example.com 197404 197404   2047  1896   125     0     0

Setting up and managing virtual instances

-----------------------------------------

Setting up virtual instances

++++++++++++++++++++++++++++

This step shows how to setup a virtual instance with either

non-mirrored disks (``plain``) or with network mirrored disks

(``drbd``).  All commands need to be executed on the Ganeti master

node (the one on which ``gnt-cluster init`` was run).  Verify that the

OS scripts are present on all cluster nodes with ``gnt-os list``.

To create a virtual instance, you need a hostname which is resolvable

(DNS or ``/etc/hosts`` on all nodes). The following command will

create a non-mirrored instance for you::

  gnt-instance add -t plain -s 1G -n node1 -o debootstrap instance1.example.com

  * creating instance disks...

  adding instance instance1.example.com to cluster config

   - INFO: Waiting for instance instance1.example.com to sync disks.

   - INFO: Instance instance1.example.com's disks are in sync.

  creating os for instance instance1.example.com on node node1.example.com

  * running the instance OS create scripts...

  * starting instance...

The above instance will have no network interface enabled. You can

access it over the virtual console with ``gnt-instance console

inst1``. There is no password for root. As this is a Debian instance,

you can modify the ``/etc/network/interfaces`` file to setup the

network interface (eth0 is the name of the interface provided to the

instance).

To create a network mirrored instance, change the argument to the *-t*

option from ``plain`` to ``drbd`` and specify the node on which the

mirror should reside with the second value of the *--node* option,

like this (note that the command output includes timestamps which have

been removed for clarity)::

  # gnt-instance add -t drbd -s 1G -n node1:node2 -o debootstrap instance2

  * creating instance disks...

  adding instance instance2.example.com to cluster config

   - INFO: Waiting for instance instance2.example.com to sync disks.

   - INFO: - device disk/0: 35.50% done, 11 estimated seconds remaining

   - INFO: - device disk/0: 100.00% done, 0 estimated seconds remaining

   - INFO: Instance instance2.example.com's disks are in sync.

  creating os for instance instance2.example.com on node node1.example.com

  * running the instance OS create scripts...

  * starting instance...

Managing virtual instances

++++++++++++++++++++++++++

All commands need to be executed on the Ganeti master node.

To access the console of an instance, run::

  gnt-instance console INSTANCENAME

To shutdown an instance, run::

  gnt-instance shutdown INSTANCENAME

To startup an instance, run::

  gnt-instance startup INSTANCENAME

To failover an instance to its secondary node (only possible with

``drbd`` disk templates), run::

  gnt-instance failover INSTANCENAME

For more instance and cluster administration details, see the

*Ganeti administrator's guide*.