Apache CloudStack 4.21 simplifies Template registration by allowing Administrators to select and register official distribution Templates directly during Zone creation. Instead of registering Templates individually after a Zone is deployed, the Zone Deployment Wizard can now prepopulate selected images automatically, making them available as soon as the Zone is ready.

In earlier Apache CloudStack releases, Template registration was handled as a separate, manual step. After a Zone was created, Administrators had to register Templates individually through the UI or API, repeating the same process for each image required. While effective, this approach added friction to the initial provisioning of a new cloud environment.

With Apache CloudStack 4.21, this workflow becomes more integrated. During Zone creation, Administrators can select which Templates should be available in the new Zone, allowing CloudStack to handle their registration and download as part of the deployment process.

As this is a newly introduced capability, the current scope is focused on new Zones. In future releases, this approach is expected to extend to the Template registration workflow for existing Zones, further unifying Template lifecycle management.

Feature Overview

For Zones using the KVM hypervisor, the Zone Deployment Wizard includes a Register Templates step that allows Administrators to prepopulate a Zone with official distribution Templates during deployment.

The Templates available in this step are defined through a metadata file located on the Management Server:

/usr/share/cloudstack-management/webapp/cloud-image-templates.json

This file describes the available Templates and includes metadata such as:

• Template name
• Supported system architecture (x86_64 or aarch64)

• Source download URL

An example entry is shown below:

 

[
    {
      "id": 1,
      "name": "Ubuntu 24.04",
      "arch": "x86_64",
      "url": "https://download.cloudstack.org/templates/cloud-images/ubuntu/ubuntu-24.04-server-cloudimg-amd64.img"
    },
    {
      "id": 2,
      "name": "Rocky Linux 9",
      "arch": "aarch64",
      "url": "https://download.cloudstack.org/templates/cloud-images/rockylinux/Rocky-9-GenericCloud.latest.aarch64.qcow2"
    }
]

Each entry corresponds to an official distribution cloud image originally published and maintained by the respective Linux distribution. The CloudStack community validates and republishes these images on the CloudStack CDN at:

https://download.cloudstack.org/templates/cloud-images

Administrators can extend the cloud-image-templates.json file by adding additional entries, allowing the Zone Deployment Wizard to register other Templates as part of Zone creation. This can include custom Linux images or pre-configured Windows Templates, provided they meet CloudStack compatibility requirements.

The wizard consumes this metadata file as input and does not impose restrictions on the operating system or image type beyond architectural compatibility. Standard licensing, image preparation, and operating system requirements still apply.

Register Template Flow in Zone Wizard

For Zones using the KVM hypervisor, the Zone Deployment Wizard includes a Register Templates step that is executed once the Zone is enabled.

At this stage, Administrators can select one or more Templates filtered by system architecture (x86_64 or aarch64), or skip the step if Templates will be registered later.

After the Zone deployment completes, CloudStack automatically:

• Registers the selected Templates in the Zone
• Downloads the images into Secondary Storage
• Makes the Templates available to create new Instances

This step integrates Template registration into the Zone creation workflow without changing existing mechanisms for managing custom or third-party Templates through the UI or API.

Conclusion

Apache CloudStack 4.21 integrates Template registration directly into the Zone Deployment workflow, allowing Administrators to make official distribution Templates available as part of Zone creation. This removes the need for separate, manual Template registration steps when bootstrapping new environments.

By sourcing Templates derived from upstream distribution images and validating them for CloudStack compatibility, this feature provides a consistent and predictable starting point for new Zones, while preserving existing mechanisms for managing custom Templates. It also establishes a foundation for tighter integration with Template lifecycle workflows in future releases.