Build Azure images

Requirements:

• Packer
• Azure access keys with the appropriate roles and permissions
• A Vanilla image
• Packer templates

The suggested approach is based on using Packer templates to customize the deployment and automate the upload and publish to Azure of cOS derivatives or cOS itself. For all the details and possibilities of Packer check the official documentation.

Run the build with Packer

Publishing an image in Azure based on top of the latest cOS Vanilla image is fairly simple. In fact, it is only needed to set the Azure credentials and run a packer build process to trigger the deployment and register the resulting snapshot as an image. In such case the latest cOS image will be deployed and configured with pure defaults. Consider:

# From the root of a cOS-toolkit repository checkout

> export AZURE_CLIENT_ID=<your_azure_client_id> 
> export AZURE_TENANT_ID=<your_azure_tenant_id> 
> export AZURE_CLIENT_SECRET=<your_azure_client_secret>
> export AZURE_SUBSCRIPTION_ID=<your_azure_subscription_id>

> cd packer
> packer build -only azure-arm.cos .

The -only azure-arm.cos flag is just to tell packer which of the sources to make use for the build. Note the packer/images.json.pkr.hcl file defines few other sources such as qemu and virtualbox.

Customize the build with a variables file

The packer template can be customized with the variables defined in packer/variables.pkr.hcl. These are the variables that can be set on run time using the -var key=value or -var-file=path flags. The variable file can be a json file including desired variables. Consider the following example:

# From the packer folder of the cOS-toolkit repository checkout

> cat << EOF > test.json
{
    "azure_location": "westeurope",
    "azure_os_disk_size_gb": 16,
    "azure_vm_size": "Standard_B2s"
}
EOF

> packer build -only azure-arm.cos -var-file=test.json .

The above example runs the Vanilla image on a 16GiB disk and calls the command elemental reset to deploy the main OS and once deployed an image is created from the running instance.

Available variables for customization

All the customizable variables are listed in packer/variables.pkr.hcl, variables with the azure_ prefix are the ones related to the Azure Packer template. These are some of the relevant ones:

• azure_cos_deploy_args: This the command that will be executed once the Vanilla image booted. In this stage it is expected that user sets a command to install the desired cOS or derivative image. By default it is set to elemental reset which will deploy the cOS image from the recovery partition. To deploy custom derivatives something like elemental reset --docker-image <my-derivative-img-ref> should be sufficient.

• azure_custom_managed_image_name: Name of a custom managed image to use for your base image.

• azure_custom_managed_image_resource_group_name: Name of a custom managed image’s resource group to use for your base image.

• azure_os_disk_size_gb: This sets the disk size of the VM that Packer launches for the build. During Vanilla image first boot the system will expand to the disk geometry. The layout is configurable with the user-data.

• azure_vm_size: Sets the size of the instance being launched. Defaults to Standard_B2s

• azure_user_data_file: This sets the user-data file that will be used for the azure instance during the build process. It defaults to user-data/azure.yaml and the default file basically includes the disk expansion configuration. It adds a COS_STATE partition that should be big enough to store about three times the size of the image to deploy. Then it also creates a COS_PERSISTENT partition with all the rest of the available space in disk.