Ganeti Exercise

About Ganeti

Ganeti is a virtual machine cluster management tool developed by Google. The solution stack uses either Xen or KVM as the virtualization platform, LVM for disk management, and optionally DRBD for disk replication across physical hosts.

Ganeti manages clusters of Xen or KVM host nodes. It controls and configures the high availability features such as instance migration, DRBD disk replication and host node failover.

You can use multiple clusters for different physical locations for example. All the nodes in the cluster expect to have very high bandwidth between them, for example for DRBD repication. If you have more than ~40 nodes in your cluster, Phil Regnauld recommends that you start a new cluster rather than adding more nodes.

About this exercise

We will install Ganeti in some virtual machines, configure it to use the Xen hypervisor, and use it to create and manage some virtual machines.

Normally you would install this on your physical hosts. We are using it in a VirtualBox virtual machine which is pretending to be our physical host, because we don’t have enough physical boxes for everyone. This forces us to use Xen (which is slower than KVM) because we can’t use KVM inside a VirtualBox virtual machine. You could use either for a real deployment. The installation process is slightly different. KVM is not covered here.

This is not a production setup! This is intended to give you hands-on experience of Ganeti and Xen on your own hardware (laptop) in a classroom environment. I will try to point out where we are taking shortcuts or unusual configurations that we would not normally do in production. NSRC has a five-day workshop on virtualisation and we have ~3 hours, so this is just an introduction!

Install the first Node (VM host machine)

Install VirtualBox or make sure you are running version 4.3 or higher.

Configure VirtualBox networking

Open VirtualBox Preferences > Network > Host-Only Adaptors. Ensure that you have at least two listed: vboxnet0 and vboxnet1. If not, click on the Add button to the right of the list to create them.

Double-click on vboxnet0 and check that the IP addresses are as follows:

And check that the DHCP server is enabled and configured for:

Enabling the DHCP server

If you have made any changes, then exit and restart VirtualBox, otherwise this change will not take effect, as we discovered after an hour of debugging!

Create a new VM called Ganeti Demo. Give it 2 GB RAM and a 40 GB VDI disk, dynamically sized.

Install the OS for each Node

Start the VM and attach the debian-8.x.x-amd64-DVD-1.iso image. Read the following sections before you start the installation, and use them at the appropriate times during the installation.


You must use a fully qualified hostname, for example If you have your own delegated DNS domain, and you know how to add A records to it, then you can use it instead!

We will need a cluster address which is separate from each host node’s address. So I will use names like this in the example:

You can use multiple clusters for different physical locations for example. All the nodes in the cluster expect to have Layer 2 (shared LAN) between them (for live migration of instances to another node) and very high bandwidth (for DRBD replication).§ If you have more than ~40 nodes in your cluster, Phil Regnauld recommends that you start a new cluster rather than adding more nodes.


The server should use LVM for disk space, so instead of the default Guided Partitioning, choose Manual, then SCSI1. Write a new partition table if prompted.

Proxy Server

If you are following this exercise at an AfNOG event, please enter this proxy server name when prompted, to save a LONG install time:

Please enter this carefully and check it. Using the wrong value will make it impossible for you to install any packages. Of course, if you are not at the AfNOG workshop then this server will no longer exist, so use a local proxy server or leave it blank.

While the installation proceeds, familiarise yourself with the terminology of Ganeti.

Software selection

Enable installation of the SSH Server and Standard system utilities, disable everything else.

Reconfigure the virtual network

After installation, shut down the machine and reconfigure its network interfaces in VirtualBox:

Configuring Network Adaptor 1

Then start the machine again. Log in on the console, edit /etc/apt/sources.list and delete the deb cdrom line. Then install some packages:

apt install bridge-utils sudo
usermod -G sudo afnog

Then edit /etc/network/interfaces to look like this:

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp

auto xen-br0
iface xen-br0 inet static
	# This must match the address of your hostname in the DNS, not the cluster address!
	bridge_ports eth1
	bridge_stp off
	bridge_fd 0

Now you should be able to reboot the host and login with SSH using the address that you assigned to xen-br0 above. SSH is much more convenient than the console, because you can copy and paste!

Enable Debian Backports

Edit /etc/apt/sources.list and add the following line:

deb jessie-backports main

Then run:

sudo apt update

Hostnames and DNS

Edit /etc/hostname and put the fully-qualified hostname (FQDN) in there. Then change the hostname to match:

hostname `cat /etc/hostname`

Edit /etc/hosts and ensure that it contains the IP address and hostname of your host. You will also need to choose a name (hostname) and IP address for your cluster, which must be different. For example:       localhost

You must use fully qualified hostnames for your nodes and for the cluster, for example, and they must all have IP addresses. If you have your own delegated DNS domain, and you know how to add A records to it, then you can use it instead!

Configure Xen

Edit /etc/default/grub and add/change the following lines to enable Xen (you would not need this for a KVM cluster in production):


This restricts the master domain to 600 MB RAM, which will make it slow, but give us more RAM free for guests. In your own configurations you should probably allocate more RAM to the host (domain 0)!

Then run the following commands:

sudo update-grub
sudo apt dist-upgrade	
sudo apt install xen-linux-system-amd64

Then reboot the host. Be sure to select a Xen kernel from the boot list. Log in again and check that the free command reports 600 MB of total Mem, not 2 GB:

afnog@ganeti:~$ free
	     total       used       free     shared    buffers     cached
Mem:        527640

Install DRBD

The Ganeti manual has instructions for this, but they are confusing and out-of-date for Debian >= Wheezy, so we skip that step and do it here instead:

sudo apt install drbd-utils

Edit /etc/modprobe.d/drbd.conf and make it look like this:

options drbd minor_count=128 usermode_helper=/bin/true

Edit /etc/modules and add the following line at the end:


Load the kernel module (driver) now:

sudo modprobe drbd

Enable Debian Backports

Edit /etc/apt/sources.list and add the following line:

deb jessie-backports main

Then run:

sudo apt update

Install Ganeti software

Start by running the following commands:

sudo apt -t jessie-backports install ganeti ganeti-instance-debootstrap

Then start following the Ganeti installation tutorial, skipping the following sections:

Create a new Ganeti cluster

You should only do this on the first node in the cluster. Do not do this step again unless you are setting up a new cluster!

Run the following command, ensuring that you use the correct cluster hostname:

sudo mkdir /root/.ssh
sudo gnt-cluster init --vg-name xenvg --enabled-hypervisors=xen-pvm -H xen-pvm:xen_cmd=xl

The gnt-cluster command should take a few minutes to complete.

Note: Normally you would use either xen-hvm or kvm as the hypervisor, instead of xen-pvm above. In this case we must use xen-pvm because we are doing this inside a virtual machine, so we can’t use the virtualisation CPU instructions because VirtualBox is already using them to run the Ganeti host node (VirtualBox guest).

Test that you can run the following useful commands and examine their output:

sudo gnt-cluster verify
sudo gnt-node list
sudo gnt-instance list
sudo gnt-job list

You can ignore the following errors and warnings from gnt-cluster verify. The error is out of date, and the warnings are not problems because not all LVM volumes are used by Ganeti.

Thu Jun  2 13:17:09 2016   - WARNING: node volume xenvg/Swap is unknown
Thu Jun  2 13:17:09 2016   - WARNING: node volume xenvg/Root is unknown

The Ganeti manual page gives useful information about Ganeti commands, including examples.

Create the file /etc/ganeti/vnc-cluster-password containing the password that you want to use for VNC access to consoles.

Test your setup

Check that the gnt-node list command shows your node:

$ sudo gnt-node list
Node                     DTotal DFree MTotal MNode MFree Pinst Sinst  40.0G 28.8G   2.0G  1.9G  126M     0     0

Warning: If you see question marks in all the columns after the node name, like this:

$ sudo gnt-node list
Node                     DTotal DFree MTotal MNode MFree Pinst Sinst      ?     ?      ?     ?     ?     0     0

that means that Ganeti cannot retrieve information about your node. Check the node daemon logfile /var/log/ganeti/node-daemon.log for possible error messages. For example, if you find this error:

ERROR Can't retrieve xen hypervisor information (exited with exit code 1): ERROR:  A different toolstack (xl) have been selected!

that means that Ganeti is trying to use the old xm command to get information, instead of the new xl command, and not getting any information. You probably forgot to add the option -H xen-pvm:xen_cmd=xl when you created the cluster. You can fix it by modifying the cluster settings on the node:

sudo gnt-cluster modify -H xen-pvm:xen_cmd=xl

and check that the gnt-node list now shows the correct information for your node.

You should also make sure that the MFree column shows at least 1 GB free (not 126 MB as in the example output above). This ensures that there is enough RAM free in the hypervisor to create new guests. Otherwise you won’t be able to do much with your new hypervisor. If it doesn’t show enough free RAM, check that you have reconfigured GRUB and run update-grub.

Add an entry to /etc/hosts for a host to use for burnin testing, for example

The burnin test will fail unless we generate a DH parameters file for SSL:

openssl dhparam -out dhparams.pem 2048
cat dhparams.pem | sudo tee -a /var/lib/ganeti/server.pem

Run the burnin test to make sure that everything is working properly:

sudo /usr/lib/ganeti/tools/burnin -o debootstrap+default -t plain --disk-size 1024 --mem-size=512 -vv

The output should end with:

- Attaching and removing disks
  * instance
    attaching a disk with name RQLX441M
    removing last disk
	Thu Jun  2 19:13:17 2016  - WARNING: Hotplug is not supported: Hotplug is not supported by this hypervisor
	Thu Jun  2 19:13:17 2016  - INFO: Modification will take place without hotplugging.
	Thu Jun  2 19:13:18 2016  - INFO: Waiting for instance to sync disks
	Thu Jun  2 19:13:18 2016  - INFO: Instance's disks are in sync
	Thu Jun  2 19:13:19 2016  - WARNING: Hotplug is not supported: Hotplug is not supported by this hypervisor
	Thu Jun  2 19:13:19 2016  - INFO: Modification will take place without hotplugging.
- Removing instances
  * instance

If this fails, you may need to remove the instance before trying again:

sudo gnt-instance remove

Create a Virtual Machine

Add a hostname (to /etc/hosts or to a DNS domain that you control) with a dummy IP address. We will use for this example.

Normally you would give it a static IP address, but we are on a DHCP network with limited IP addresses here.

Use the following command to create the test VM:

sudo gnt-instance add -t plain --disk 0:size=4G -B memory=512 \
	-H xen-pvm:initrd_path=/boot/initrd-3-xenU -o debootstrap+default \

This new VM will have the following settings:

The output should look like this:

Wed Jun  1 11:15:37 2016 * disk 0, size 4.0G
Wed Jun  1 11:15:37 2016 * creating instance disks...
Wed Jun  1 11:15:37 2016 adding instance to cluster config
Wed Jun  1 11:15:37 2016 adding disks to cluster config
Wed Jun  1 11:15:38 2016  - INFO: Waiting for instance to sync disks
Wed Jun  1 11:15:38 2016  - INFO: Instance's disks are in sync
Wed Jun  1 11:15:38 2016  - INFO: Waiting for instance to sync disks
Wed Jun  1 11:15:39 2016  - INFO: Instance's disks are in sync
Wed Jun  1 11:15:41 2016 * running the instance OS create scripts...

If it doesn’t, look for an error message in the output or in /var/log/ganeti/jobs.log. Most likely one of the gnt-instance parameters was missing or incorrect.

Check that your new instance appears in the output of gnt-instance list, with status running:

afnog@ganeti:/tmp$ sudo gnt-instance list
Instance         Hypervisor OS                  Primary_node                 Status  Memory xen-pvm    debootstrap+default running   512M

Connect to its console:

sudo gnt-instance console

You should see it boot up (if you’re not too late) or a login prompt. If it’s not running, you can try to start it again and connect to the console quickly to see what happened:

sudo gnt-instance start
sudo gnt-instance console

You can exit the console by pressing ^] (Ctrl+]).

You should be able to login as root with no password at the console. Add a normal user and change the root password:

adduser afnog
passwd root

And edit /etc/network/interfaces to configure networking, making it look like this:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

Then tell it to reboot and watch it come back up. Check that you can access the internet from the guest. You should also be able to access the guest from your host computer, and hopefully from the local network too, using its IP address (assigned by DHCP).

Add a second Node

We want to create a replicating Instance (virtual machine) with high availability, so we need a second Node to host the backup copy of this Instance.

Create a new virtual machine and configure it using the same instructions as above, up to the point of creating a cluster, but don’t create a new cluster. Use a different hostname, for example, which must also be listed in /etc/hosts. The /etc/hosts file should be exactly the same on both hosts.

Enable remote root logins by SSH on the new server, by editing /etc/ssh/sshd_config and changing the PermitRootLogin setting to yes. Restart the ssh service.

Now add this node to the existing cluster, by running the following command on a node already in the cluster (ganeti1):

sudo gnt-node add

This will prompt you to login as root to the new node (ganeti2) and will forcibly add it to the cluster. Do not do this to a node which is already in a cluster, as it will probably result in data loss!

Verify the cluster again:

sudo gnt-cluster verify

Test HA with DRBD replication

We can now use the same burnin command with a different storage type, drbd, which will create an instance that replicates its data to another node:

sudo /usr/lib/ganeti/tools/burnin -o debootstrap+default -t drbd --disk-size 1G --mem-size=600 -vv

Install snf-image

This tool allows you to install many different distributions in a Ganeti instance, not just Debian 7. Unfortunately there are some problems with the packaging at the moment, so we need to download and install it manually:

sudo apt install curl mbr python-prctl python-scapy
sudo wget
sudo dpkg -i snf-image_0.19-1~jessie_all.deb

When asked for the URL to download snf-image-helper image from, if you are following this at an AfNOG event then you can use the copy that we downloaded for you, which will be much faster, by entering this URL:

Enable Remote API

Choose a username and password for your remote account (jack and mypassword in this case) and generate a hash using echo and openssl md5 like this:

$ echo -n 'jack:Ganeti Remote API:mypassword' | openssl md5
(stdin)= 5ede44dba4dd4e9ce3909246515b2cdc

Insert them both into /var/lib/ganeti/rapi/user, prefixing the password hash with {ha1}, and giving this user write permissions:

jack	{ha1}5ede44dba4dd4e9ce3909246515b2cdc	write

Install the Web Manager

Run the following commands:

sudo apt install git libssl-dev virtualenv
cd /tmp
tar xzvf 0.11.1.tar.gz
cd ganeti_webmgr-0.11.1

We are using Ganeti Web Manager 0.11.1, which has a bug that we need to fix before we install:

cd ganeti_webmgr/ganeti_web/settings
cd .././..

Then we can run the installation script:

sudo ./scripts/

Edit the file scripts/vncauthproxy/init-systemd and if the last line contains only a ~ character, delete it. Also, in the [Service] section, add the following line:

Then copy it to the systemd service directory, and start it:

sudo cp scripts/vncauthproxy/init-systemd /lib/systemd/system/vncauthproxy.service
sudo mkdir /var/log/vncauthproxy /var/run/vncauthproxy
sudo chown www-data /var/log/vncauthproxy /var/run/vncauthproxy
sudo service vncauthproxy start
sudo cp ganeti_webmgr/ganeti_web/settings/config.yml.dist /opt/ganeti_webmgr/config/config.yml

Edit /opt/ganeti_webmgr/config/config.yml and change the EMAIL_HOST and DEFAULT_FROM_EMAIL lines, so that their values refer to your outbound server and your email address.

Also find this line:

NAME: /opt/ganeti_webmgr/ganeti.db

And change it to:

NAME: /opt/ganeti_webmgr/db/ganeti.db

Then finish the installation:

cd /opt/ganeti_webmgr
sudo mkdir .settings db whoosh_index
sudo chown www-data .settings db whoosh_index
export DJANGO_SETTINGS_MODULE=ganeti_webmgr.ganeti_web.settings
sudo -E -u www-data bin/ syncdb --migrate
sudo -E -u www-data bin/ refreshcache
sudo -E -u www-data bin/ rebuild_index
sudo -E -u www-data bin/ collectstatic

Enter a username, password and email address for a super user for the Ganeti web manager.

Now start the web server in debugging mode:

cd /opt/ganeti_webmgr
sudo -E -u www-data bin/ runserver --insecure

This will start the debugging webserver on port 8000, so you can check that everything is working by visiting You should get a white page with a login and password box, but no styling (colours, images, etc.) If not, check the console output for error messages.

Create the file /opt/ganeti_webmgr/ with the following contents:

import os
import sys

path = '/opt/ganeti_webmgr'

# activate virtualenv
activate_this = '%s/venv/bin/' % path
execfile(activate_this, dict(__file__=activate_this))

# add project to path
if path not in sys.path:

    # configure django environment
    os.environ['DJANGO_SETTINGS_MODULE'] = 'ganeti_webmgr.ganeti_web.settings'

    import django.core.handlers.wsgi
    application = django.core.handlers.wsgi.WSGIHandler()

Create the file /etc/apache2/sites-enabled/ganeti.conf with the following contents:

WSGIPythonHome /opt/ganeti_webmgr/venv
WSGISocketPrefix /var/run/wsgi
WSGIRestrictEmbedded On

<VirtualHost *:80>
	ServerName ganeti-server.local

	# Static content needed by Django
	Alias /static "/opt/ganeti_webmgr/collected_static/"
	<Location "/static">
		Order allow,deny
		Allow from all
		SetHandler None

	# Django settings - AFTER the static media stuff
	WSGIScriptAlias / /opt/ganeti_webmgr/
	WSGIDaemonProcess ganeti processes=1 threads=10 display-name='%{GROUP}' deadlock-timeout=30
	WSGIApplicationGroup %{GLOBAL}
	WSGIProcessGroup ganeti

	# Possible values include: debug, info, notice, warn, error, crit,
	# alert, emerg.
	LogLevel warn

	<Location />
		Require all granted

Now you should be able to access (without the :8000 port specification) and see the login page with graphics:

Ganeti Login Screen

Log in using the superuser account that you created during the syncdb command, or if you have forgotten the details, run this command to create a new one:

sudo -u www-data venv/bin/python createsuperuser

Choose Clusters from the menu on the left, and then click Add Cluster in the top right. Enter the following details:

Leave the other details blank, and click Add. Your new cluster should then appear with its specifications:

Ganeti Manager showing the new cluster