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Slow Azure VM Start operations when extensions are "Failed"
Summary
You might experience slow Microsoft Azure Virtual Machine (VM) Start or Redeploy operations when one or more of the VM extensions are in a Failed state. This article discusses possible causes of this issue and resolutions.
Important
New! Try VM assist to resolve top issues. We recommend that you run VM assist for Windows or VM assist for Linux. These script-based diagnostic tools help you identify common issues that affect the Azure VM Guest Agent and overall VM health.
If you're experiencing performance problems on VMs, run these tools first before you contact Microsoft Support.
Symptoms
Although the Azure VM guest OS is active and working, and the VM can connect successfully, the operation still appears to run in the Azure portal.
Cause
VM extensions are software components that run inside the VM to enable configuration management, security, monitoring, and other features. VM extensions have a 90-minute provisioning timeout. They must complete their installation or update within that time limit. Typically, Azure doesn't continuously retry the failed extension immediately. Instead, the retry process is triggered the next time that a VM operation occurs that re-engages extension provisioning (such as Start or Redeploy). This retry behavior can delay completion of the operation until the extension either succeeds or times out again.
If an Azure VM has one or more VM extensions stuck in a Failed state, you might notice that management operations (for example, Start or Redeploy) take much longer than expected. This delay occurs because the Azure platform treats extension provisioning as part of the overall VM operation workflow. Before the operation can be marked as completed, Azure tries to reprovision any extensions that previously failed. Therefore, the VM can remain in a Starting or Updating state for an extended period even if the guest OS is already running and you could still connect to it.
More information
To mitigate this issue, follow these steps:
To determine the root cause of the failure, review the extension status and logs for the VM.
To check the status of the extensions that are installed on the VM, go to the VM blade, and then select the extensions + applications option under Settings in the left pane. If the status isn't Provisioning Succeeded, the extension might have to be removed or investigated further.
👁 Screenshot of the portal showing the extensions and applications statuses. Status is highlighted.
- Logs for the extensions can be found within the Guest OS of the VM. For more information, see the References section.
Check the status of the VM "Guest Agent" that's responsible for provisioning the extensions. If the "Guest Agent" isn't in a ready state, a review might be required. For more guidance, refer to the documents that are mentioned in the References section.
👁 Screenshot of the portal showing the VM overview. Agent status and Agent version are highlighted.
Resolve the extension failure by either fixing the configuration or uninstalling the extension. You can use the Azure portal, PowerShell, CLI, or REST API to update or remove the extension. If the issue is related to the extension functionality or compatibility, you might have to contact the extension publisher for support.
Stop and then restart the VM to verify that the extension provisioning succeeds and the VM Start operation finishes faster. You can use the Azure portal, PowerShell, CLI, or REST API to do these operations.
References
For more guidance to troubleshoot the Azure VM Guest Agent and extension issues, see:
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