vCenter Contextualization and Customization

In OpenNebula you have two options if you want to prepare the guest OS on boot:

vCenter Contextualization

OpenNebula uses a method called contextualization to send information to the VM at boot time. Its most basic usage is to share networking configuration and login credentials with the VM so it can be configured.

Prepare the Virtual Machine Image

Step 1. Start a VM with the OS you want to Customize

Supported contextualization packages are available for the following OS’s:

  • CentOS/RHEL >= 6
  • Debian >= 6
  • Ubuntu >= 11.10
  • Windows >= 7
  • Windows Server >= 2008

If you already happen to have a VM or Template in vCenter with the installed OS you can start it and prepare it to be used with OpenNebula. Alternatively you can start an installation process with the OS media.

Step 2. Download Contextualization Packages to the VM

CentOS/RHEL 6.x

wget https://github.com/OpenNebula/addon-context-linux/releases/download/v5.8.0/one-context-5.8.0-1.el6.noarch.rpm

CentOS/RHEL 7.x

wget https://github.com/OpenNebula/addon-context-linux/releases/download/v5.8.0/one-context-5.8.0-1.el7.noarch.rpm

OpenSUSE 42,15 / SLES 12

wget https://github.com/OpenNebula/addon-context-linux/releases/download/v5.8.0/one-context-5.8.0-1.suse.noarch.rpm

Debian/Ubuntu/Devuan

wget https://github.com/OpenNebula/addon-context-linux/releases/download/v5.8.0/one-context_5.8.0-1.deb

Alpine Linux

wget https://github.com/OpenNebula/addon-context-linux/releases/download/v5.8.0/one-context-5.8.0-r1.apk

FreeBSD 11,12

wget https://github.com/OpenNebula/addon-context-linux/releases/download/v5.8.0/one-context-5.8.0_1.txz

Windows

Download the MSI package into C:\:

Or execute this command in powershell:

(New-Object Net.WebClient).DownloadFile("https://github.com/OpenNebula/addon-context-windows/releases/download/v5.8.0/one-context-5.8.0.msi", "C:\one-context-5.8.0.msi")

Step 3. Install Contextualization Packages and Dependencies

CentOS/RHEL 6

yum install -y epel-release
yum install -y one-context-[0-9]*el6*rpm

CentOS/RHEL 7

yum install -y epel-release
yum install -y one-context-[0-9]*el7*rpm

OpenSUSE

zypper --no-gpg-check install -y one-context-[0-9]*suse*rpm

Debian/Ubuntu/Devuan

apt-get purge -y cloud-init
dpkg -i one-context_*deb || apt-get install -fy

Alpine Linux

apk add --allow-untrusted one-context-[0-9]*apk

FreeBSD

pkg install -y curl bash sudo base64 ruby open-vm-tools-nox11
pkg install -y one-context-[0-9]*.txz

Windows

Double-click on the downloaded MSI package icon in the same way you open other documents to install it.

Step 4. Install VMware Tools

CentOS, Debian/Ubuntu

open-vm-tools are installed as a dependency of contextualization package.

Windows

In vCenter open the VM menu, go to “Guest OS” section, click in “Install VMware Tools...” and follow the instructions.

Step 5. Run Sysprep in Windows Machines

Execute sysprep to prepare the OS for duplication. You can find more information at:

https://technet.microsoft.com/en-us/library/cc721940(v=ws.10).aspx

Step 6. Power Off the Machine and Save it

These are the steps needed to finish the preparation and import it to OpenNebula:

  • Power off the machine so it is in a consistent state the next time it boots.
  • Make sure that you take out any installation media used in the previous steps.
  • Convert the VM into a Template following this procedure
  • Import in OpenNebula, the datastores where the template’s virtual hard disks are located.
  • Import the template in OpenNebula.

The last two steps can be done using Sunstone or the CLI as explained in the Import vCenter Resources section

Set Up the Virtual Machine Template

The Virtual Machine Template has a section called context where you can automate different configuration aspects. The most common attributes are network configuration, user credentials and startup scripts. These parameters can be both added using the CLI to the template or using Sunstone Template wizard. Here is an example of the context section using the CLI:

CONTEXT = [
    TOKEN = "YES",
    NETWORK = "YES",
    SSH_PUBLIC_KEY = "$USER[SSH_PUBLIC_KEY]",
    START_SCRIPT = "yum install -y ntpdate"
]

In the example we are telling OpenNebula to:

  • Set OneGate token and onegate information in the context
  • Add network configuration to the Virtual Machine
  • Enable login into the Virtual Machine using ssh with the value of the user’s parameter SSH_PUBLIC_KEY
  • On Virtual Machine boot execute the command yum install -y ntpdate

OneGate Token

OpenNebula has a centralized service to share data between Virtual Machines and the main daemon, useful to set monitoring information that can be gathered inside the VM and configuration data. It also lets you send scaling actions when the Virtual Machine belongs to a Service.

To do so the client installed with the contextualization packages (onegate) needs some information:

  • Token: it’s the key specific to each VM used to authenticate with the service
  • OneGate endpoint: the address where the OneGate daemon is reachable

To fill this information you have to specify TOKEN = "YES" in the contextualization section.

Network Configuration

OpenNebula does not rely on a DHCP server to configure networking in the Virtual Machines. To do this configuration it injects the network information in the contextualization section. This is done with option NETWORK = "YES". When OpenNebula finds this option it adds the IP information for each of the network interfaces configured plus extra information that resides in the Virtual Network template, like DNS, gateway and network mask.

The parameters used from the Virtual Network template are explained in the Managing Virtual Networks section.

User Credentials

One of the other very important things you have to configure is user credentials to connect to the newly created Virtual Machine. For linux base images we recommend to use SSH public key authentication and using it with OpenNebula is very convenient.

The first thing the users should do its to add their SSH public key (or keys) to its OpenNebula user configuration. This can be done in the Settings section of the web interface or using the command line interface:

oneuser update myusername
# an editor is opened, add this line
SSH_PUBLIC_KEY="ssh-rsa MYPUBLICKEY..."

Then in the Virtual Machine Template we add the option:

CONTEXT = [
    SSH_PUBLIC_KEY = "$USER[SSH_PUBLIC_KEY]"
]

Using this system the new Virtual Machines will be configured with the SSH public key of the user that instantiated it.

For Windows machines SSH is not available but you can use the options USERNAME and PASSWORD to create and set the password of an initial administrator.

CONTEXT = [
    USERNAME = "Administrator",
    PASSWORD = "VeryComplexPassw0rd"
]

Execute Scripts on Boot

To be able to execute commands on boot, for example, to install some software, you can use the option START_SCRIPT. When this option is used a new file that contains the value of the option will be created and executed.

For Windows machines this is a PowerShell script. For linux machines this can be any scripting language as long as it is installed in the base image and the proper shebang line is set (shell scripts don’t need shebang).

In this example some commands will be executed using bash shell that will install the package ntpdate and set the time.

CONTEXT = [
    START_SCRIPT = "#!/bin/bash
yum update
yum install -y ntpdate
ntpdate 0.pool.ntp.org"
]

To add more complex scripts you can also use the option START_SCRIPT_BASE64. This option gets a base64 encoded string that will be decoded before writing the temporary script file.

Advanced Contextualization

There are more options that can be set in the contextualization section. You can read about them in the Virtual Machine Definition File reference section

vCenter Customization

vCenter offers a way to prepare the guest OS on boot. For example configuring its network, licenses, Active Directory server, etc. OpenNebula vCenter drivers offers a way to tie one OpenNebula template with one of these customizations so it is applied on VM startup. You can get more information about this system in VMware documentation.

There are a couple of things to take into account:

  • It only works with OpenNebula vcenter driver.
  • This system is not compatible with OpenNebula contextualization as this customization overwrites the networking changes made by context scripts.
  • VM network configuration must be done externaly to OpenNebula. Either with a DHCP server or manually setting IPs for each interface.
  • This method can be used in all the Guest OSs supported by vCenter.

Applying Customization to one Template Using Sunstone

For vcenter templates there are two options in the context tab. To use vCenter Customization select “vCenter” in the as “Contextualization type”. This will show a dropdown with all the customizations from all the hosts. There you can select from these possibilities:

  • None: No customization will be applied
  • Custom: You will be able to type manually the name of one customization
  • The name of customizations found in vCenters
../../_images/vcenter_customization_step1.png

Make sure that the customization applied is available in the vCenter where the VM template reside.

Once we update the template, we’ll get a VCENTER_CUSTOMIZATION_SPEC attribute inside the USER_TEMPLATE section.

../../_images/vcenter_customization_step2.png

Getting the Available Customizations per Cluster

OpenNebula monitoring probes get the list of available customization specifications per cluster. You can get the list with the command onehost show. Look for CUSTOMIZATION data in MONITORING INFORMATION. For example:

$ onehost show 20
[...]
MONITORING INFORMATION
...
CUSTOMIZATION=[
  NAME="linux-customization",
  TYPE="Linux" ]
CUSTOMIZATION=[
  NAME="custom",
  TYPE="Windows" ]

Applying Customization to a template Using CLI

To add a customization specification to one template a parameter called VCENTER_CUSTOMIZATION_SPEC must be added inside the USER_TEMPLATE section. Take for example this template:

CPU = "1"
DESCRIPTION = "vCenter Template imported by OpenNebula from Cluster Cluster"
DISK = [
  IMAGE_ID = "124",
  IMAGE_UNAME = "oneadmin",
  OPENNEBULA_MANAGED = "NO" ]
GRAPHICS = [
  LISTEN = "0.0.0.0",
  TYPE = "VNC" ]
HYPERVISOR = "vcenter"
LOGO = "images/logos/linux.png"
MEMORY = "256"
NIC = [
  NETWORK_ID = "61",
  OPENNEBULA_MANAGED = "NO" ]
OS = [
  BOOT = "" ]
SCHED_REQUIREMENTS = "ID=\"20\""
VCENTER_CCR_REF = "domain-c14"
VCENTER_INSTANCE_ID = "4946bb10-e8dc-4574-ac25-3841bcf189b9"
VCENTER_RESOURCE_POOL = "Dev6ResourcePool/nested/tino"
VCENTER_TEMPLATE_REF = "vm-2353"
VCENTER_VM_FOLDER = ""
VCPU = "1"

To use the customization named LinuxCustomization shown in the previous section we can add the option VCENTER_CUSTOMIZATION_SPEC="LinuxCustomization" as this:

CPU = "1"
DESCRIPTION = "vCenter Template imported by OpenNebula from Cluster Cluster"
DISK = [
  IMAGE_ID = "124",
  IMAGE_UNAME = "oneadmin",
  OPENNEBULA_MANAGED = "NO" ]
GRAPHICS = [
  LISTEN = "0.0.0.0",
  TYPE = "VNC" ]
HYPERVISOR = "vcenter"
LOGO = "images/logos/linux.png"
MEMORY = "256"
NIC = [
  NETWORK_ID = "61",
  OPENNEBULA_MANAGED = "NO" ]
OS = [
  BOOT = "" ]
SCHED_REQUIREMENTS = "ID=\"20\""
USER_TEMPLATE = [
  VCENTER_CUSTOMIZATION_SPEC = "LinuxCustomization" ]
VCENTER_CCR_REF = "domain-c14"
VCENTER_INSTANCE_ID = "4946bb10-e8dc-4574-ac25-3841bcf189b9"
VCENTER_RESOURCE_POOL = "Dev6ResourcePool/nested/tino"
VCENTER_TEMPLATE_REF = "vm-2353"
VCENTER_VM_FOLDER = ""
VCPU = "1"