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
Step 2. Download Contextualization Packages to the VM¶
OpenSUSE 42,15 / SLES 12¶
Download the MSI package into
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¶
yum install -y epel-release yum install -y one-context-[0-9]*el6*rpm
yum install -y epel-release yum install -y one-context-[0-9]*el7*rpm
zypper --no-gpg-check install -y one-context-[0-9]*suse*rpm
apt-get purge -y cloud-init dpkg -i one-context_*deb || apt-get install -fy
apk add --allow-untrusted one-context-[0-9]*apk
pkg install -y curl bash sudo base64 ruby open-vm-tools-nox11 pkg install -y one-context-[0-9]*.txz
Double-click on the downloaded MSI package icon in the same way you open other documents to install it.
Step 4. Run Sysprep in Windows Machines¶
sysprep to prepare the OS for duplication. You can find more information at:
Step 5. Power Off the Machine and Save it¶
After these configuration is done you should power off the machine, so it is in a consistent state the next time it boots. Then you will have to save the image.
If you are using OpenNebula to prepare the image you can use the command
onevm disk-saveas, for example, to save the first disk of a Virtual Machine called “centos-installation” into an image called “centos-contextualized” you can issue this command:
onevm disk-saveas centos-installation 0 centos-contextualized
Using sunstone web interface you can find the option in the Virtual Machine storage tab.
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
- On Virtual Machine boot execute the command
yum install -y ntpdate
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
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.
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
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.