install.rst

Ganeti installation tutorial

Documents Ganeti version 2.0

Contents

• Introduction
• Installing the base system and base components
  • Hardware requirements
  • Installing the base system
    • Hostname issues
  • Installing Xen
    • Xen settings
    • Selecting the instance kernel
  • Installing DRBD
  • Other required software
• Setting up the environment for Ganeti
  • Configuring the network
  • Configuring LVM
  • Installing Ganeti
  • Installing the Operating System support packages
  • Initializing the cluster
  • Joining the nodes to the cluster
  • Separate replication network
  • Testing the setup
• Setting up and managing virtual instances
  • Setting up virtual instances
  • Managing virtual instances

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.

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).

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.

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.

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.

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.

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).

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/

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.

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

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.

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.

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 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.