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Azure VM images

Muchos can be configured to use any Azure Marketplace image, including those that need a payment plan. In addition, Muchos can be configured to use a custom VM image which has been uploaded to an Azure subscription, or a VM image which exists in a shared image gallery.

Cluster image configuration

The sections below describe the various image related configurations in muchos.props.

azure_image_reference

azure_image_reference is a pipe-delimited string in the format offer|publisher|sku|version|image_id|. The trailing pipe character is intentional.

  • For Azure Marketplace images, the values for the fields offer|publisher|sku|version can be obtained from the Azure portal, or by using the Azure CLI commands as shown later. For example, the AlmaLinux 9 image which is used as the default for Azure clusters in Muchos is specified as:

    azure_image_reference = almalinux-x86_64|almalinux|9-gen2|latest||

    In the above case, since it's a marketplace image, the last value of image_id is empty. In addition, an Alma Linux 9 specific cloud-init file is specified. This cloud-init file installs rsync which seems to not be included in Alma Linux 9 images:

    azure_image_cloud_init_file = cloud-init-alma9.yml

    The Rocky Linux images in Azure require plan information to be supplied. Currently, the Rocky Linux 8 image has been verified to work correctly. For using Rocky Linux 8 instead of Alma Linux, here is what you can use in muchos.props. The image plan information is mandatory for this image:

    • azure_image_reference = rockylinux-x86_64|resf|8-base|latest||
    • azure_image_plan = 8-base|rockylinux-x86_64|resf|

    In addition, you might need to manually view and accept the terms of use for the Rocky Linux image, before being able to use it within Muchos. See the azure_image_plan section below for details.

    Note: The Rocky Linux 9 image on Azure has an issue with data disks not being correctly mapped to paths under /dev/disk/azure/scsi1. This is either an image issue, or an issue with the Microsoft Azure Linux Guest Agent. Till the issue is diagnosed and fixed, we do not recommend using the Azure Rocky Linux 9 image at this point in time.

  • It is also possible to use a custom Azure image with Muchos. For using an image from an Azure Compute Gallery ("Shared Image Gallery"), the full resource ID of the image should be specified for image_id and the other fields should not be specified. For example:

    ||||//subscriptions/AZURE_SUBSCRIPTION_ID/resourceGroups/RESOURCE_GROUP/providers/Microsoft.Compute/galleries/SHARED_GALLERY_NAME/images/SHARED_IMAGE_NAME/versions/SHARED_IMAGE_VERSION|

    For more information on creating an image in an Azure compute gallery, see Tutorial: Create a custom image of an Azure VM with the Azure CLI. Some Linux distributions like Fedora make available a VHD file specifically for Azure which can then be converted to a fixed-size disk and uploaded to Azure for creating a custom image. In the case of the Fedora image, the Fedora-Cloud-Base-Azure-39-1.5.x86_64.vhd needs to be resized to a fixed-size VHD of size 6,442,450,944 bytes before uploading to Azure.

  • For legacy managed images (not from a gallery), the full resource ID of the image should be specified in place of image_id, and the other fields should not be specified. For example:

    ||||/subscriptions/AZURE_SUBSCRIPTION_ID/resourceGroups/RESOURCE_GROUP/providers/Microsoft.Compute/images/CUSTOM_IMAGE_NAME|

    For more information on legacy managed images see Create a legacy managed image of a generalized VM in Azure.

azure_image_plan

azure_image_plan is only needed when working with images which require payment plan information to be supplied when a VM or VMSS is being created using that image. The format of this configuration is plan_name|product|publisher|. Plan information for the images published by a given publisher can easily be queried by using the Azure CLI. For example, to query the plan information for a Rocky Linux image in Azure:

az vm image show --urn "resf:rockylinux-x86_64:8-base:latest" --query "plan"

Then using that information, azure_image_plan can be configured as below in muchos.props:

azure_image_plan = 8-base|rockylinux-x86_64|resf|

More information about purchase plans, and accepting terms, etc. is available here.

azure_image_cloud_init_file

azure_image_cloud_init_file is used to optionally specify the name of a cloud-init file to be used. Only specify the filename here, and make sure that the file exists under the ansible/roles/azure/files directory in this repo.

Proxy image configuration

If needed, there are optional configurations to allow using a different image for the optional proxy. The following configurations follow exactly the same formats as their cluster image counterparts.

  • azure_proxy_image_reference
  • azure_proxy_image_plan
  • azure_proxy_image_cloud_init_file

By default, these configurations are commented out in the muchos.props file, and the corresponding values from the cluster image configurations are used.

Other useful commands

You can run the below Azure CLI command to determine the list of SKU's available for a given product and publisher in a given region:

az vm image list-skus -l <region> -f AlmaLinux -p AlmaLinux -o table

For illustration, provided a sample output that displays the sku list from westus2 region. The sku name 8-gen1, 8-gen2 refer to Azure VMs generations.

$ az vm image list-skus -l westus2 -f AlmaLinux -p AlmaLinux -o table
Location    Name
----------  --------
westus2     8-gen1
westus2     8-gen2
westus2     8_4
westus2     8_4-gen2
westus2     8_5
westus2     8_5-gen2
westus2     9-gen1
westus2     9-gen2