Microsoft Azure

Hello everyone,

I'm encountering a recurring issue when trying to deploy Azure Virtual Machines using custom images. After the deployment, the VMs are stuck in a boot loop or fail to acquire an IP address, resulting in inaccessible instances. I've followed the recommended practices for generalized VMs using Sysprep, but the problem persists.

Has anyone else faced similar challenges with custom images, specifically around boot failures? I'm using a Windows Server 2019 base image with some pre-installed applications and configurations. I've checked the boot diagnostics, and it shows generic error messages like "OS did not boot correctly."

Any guidance on potential causes or troubleshooting steps would be greatly appreciated!

Hi AzureUser123,

I've seen this behavior before, and it often stems from issues during the Sysprep process or specific configurations that don't translate well to the Azure environment.

Some common culprits include:
1. **Driver Conflicts:** Ensure all necessary drivers (especially storage and network drivers for Azure) are present and correctly installed before generalizing. Sometimes, specific third-party drivers can cause problems.
2. **Windows Update Issues:** Make sure the image is fully patched before Sysprep. Corrupted updates or pending updates can interfere with the generalization process.
3. **Unattended Answer File (.xml):** If you're using an `unattend.xml` file for automation, double-check its syntax and ensure it doesn't contain any settings that might conflict with Azure's provisioning.
4. **Out-of-Box Experience (OOBE) Settings:** Certain OOBE settings during Sysprep might need to be adjusted for Azure deployment. Specifically, ensure the VM is not configured to automatically log in with specific credentials if you're relying on Azure's agent for initial setup.

Try running Sysprep with `/generalize /oobe /shutdown /unattend:YourAnswerFile.xml` (if applicable). After shutdown, capture the image and deploy a VM from it. Also, check the VM's serial console logs in the Azure portal for more detailed error messages than what's in the standard boot diagnostics.

Echoing SudoMaster's points. I also found that any software that heavily modifies the registry or system services (like certain security agents or monitoring tools) could cause issues after generalization if not properly handled. Make sure you're removing any potentially problematic software or services before Sysprep.

Another quick check: is the VM SKU you're deploying from the custom image compatible with the image itself? Sometimes, older image versions might have compatibility issues with newer VM sizes.