Azure Virtual Machines

Virtual Machine Images

Azure Virtual Machines (VMs) are powered by images. An image is a template that contains the operating system and any pre-installed software required to launch a virtual machine. Azure provides a rich gallery of pre-defined images, and you can also create and use your own custom images.

Understanding VM Images

Images are categorized in several ways:

• Platform Images: These are images provided by Microsoft and its partners, including various versions of Windows Server, Ubuntu, CentOS, Red Hat Enterprise Linux, and more.
• Marketplace Images: A curated collection of software and services that can be deployed on Azure, often with pre-configured operating systems and applications.
• Custom Images: Images you create from your own virtual machines or capture from existing disks. This is ideal for deploying consistent environments or applications.
• Shared Image Gallery: A service that helps you manage, share, and version your VM images across your Azure subscriptions and beyond.

Popular VM Image Sources

You can access and select images directly from the Azure portal when creating a virtual machine. Here are some common sources:

Creating Custom Images

You can generalize a VM and then capture it to create a custom image. This process involves:

1. Deploying a VM from a desired OS image.
2. Configuring the VM with your specific applications and settings.
3. Generalizing the VM using tools like Sysprep for Windows or WA agent for Linux.
4. Deallocating and stopping the VM.
5. Capturing the VM to create a managed image or adding it to a Shared Image Gallery.

You can also create custom images from existing VHD files.

Using Azure Compute Gallery (formerly Shared Image Gallery)

Azure Compute Gallery is the recommended way to manage and share VM images:

• Version Control: Create multiple versions of an image.
• Regional Replication: Replicate images to different Azure regions for faster deployments.
• Access Control: Define who can use your images with Azure RBAC.
• Image Definitions: Organize your images logically.

Key Considerations

• OS Licensing: Understand the licensing implications for different operating systems.
• Image Updates: Keep your images updated with the latest security patches and software versions.
• Image Size: Larger images can lead to longer deployment times and higher storage costs.
• Generalization: Ensure your custom images are properly generalized to avoid conflicts when deploying multiple VMs from the same image.

For detailed steps and advanced configurations, please refer to the official Azure documentation.