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Adesola Kehinde
Adesola Kehinde

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Creating a Virtual Machine Scale Set (VMSS) from Your Captured Image

In the last blog, we captured a custom Windows VM image using Azure Compute Gallery. Now, we're going to use that image to create a Virtual Machine Scale Set (VMSS). This allows you to automatically scale up or down based on demand. Let's dive in.

🧭 Step 1: Go to Azure Compute Gallery

  • From the Azure Portal home, search for "Azure Compute Gallery".
  • Open the gallery you created earlier. Image description

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📸 Step 2: Select Your Image

  • Click on the image you previously captured.
  • It should have the type marked as Specialized (remember, we chose specialized because we didn't generalize our VM).

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💡 Why specialized?

A specialized image retains all the settings and configurations exactly as they were on your VM. This is useful for cloned environments or when you're not using Sysprep.

🛠️ Step 3: Create a VMSS

  • In the image's overview page, click "Create VMSS".
  • Provide a Scale Set Name.
  • Choose your Region.
  • Under Orchestration Mode, select Flexible.

💡 Why Flexible Orchestration Mode?

Flexible mode gives you more control over scaling and VM instances. It's ideal for mixed workloads or when VM identity and persistence matter.

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⚙️ Step 4: Configure Scaling Options

  1. Under the Scaling tab, enable automatic scaling.
  2. Add a new scaling condition:
    • Condition Name: e.g., scale-on-demand
    • Instance Count: e.g., 2
    • Minimum: 1
    • Maximum: 5
    • Scale Out: Increase count by 1
    • Scale In: Decrease count by 1
  3. Click Save.

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🔐 Step 5: Admin Credentials (Blurred Out?)

You may notice the admin username, password, and confirm password fields appear blurred or disabled.

🧠 Why is that?

Because you're using a specialized image — the credentials are already baked into the image. Azure doesn't require you to reset or re-enter them.

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✅ Step 6: Review and Create

  • Review your configuration.
  • Make sure tags, VM size, network, and scaling settings are correct.
  • Click Create to deploy the VMSS.

⏳ After a few minutes, your scale set will be up and running!

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🎯 Final Thoughts

You’ve now:

  • Reused a custom VM image
  • Created a scale set
  • Configured scaling policies
  • Understood why certain options (like specialized images and flexible orchestration) matter

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