Hotpatching in Azure is a preview feature that enables to apply updates without restarting Windows Server Azure VM. This new feature relies on Windows Server Azure Edition VM which is a new Windows Server image. This feature is available in preview for all Azure regions. Some providers need to be registered but we will talk about that later.

The Microsoft Docs presents how work this feature:

Hotpatch works by first establishing a baseline with a Windows Update Latest Cumulative Update. Hotpatches are periodically released (for example, on the second Tuesday of the month) that build on that baseline. Hotpatches will contain updates that don’t require a reboot. Periodically (starting at every three months), the baseline is refreshed with a new Latest Cumulative Update.

Hotpatch sample schedule

There are two types of baselines: Planned baselines and unplanned baselines.

  • Planned baselines are released on a regular cadence, with hotpatch releases in between. Planned baselines include all the updates in a comparable Latest Cumulative Update for that month and require a reboot.
    ○ The sample schedule above illustrates four planned baseline releases in a calendar year (five total in the diagram), and eight hotpatch releases.
  • Unplanned baselines are released when an important update (such as a zero-day fix) is released, and that particular update can’t be released as a Hotpatch. When unplanned baselines are released, a hotpatch release will be replaced with an unplanned baseline in that month. Unplanned baselines also include all the updates in a comparable Latest Cumulative Update for that month, and also require a reboot.
    ○ The sample schedule above illustrates two unplanned baselines that would replace the hotpatch releases for those months (the actual number of unplanned baselines in a year isn’t known in advance).

In this topic, I’ll show you how to try hotpatching for Windows Server Azure Edition VM.

Register Hotpatch Provider

Before using this feature, you need to register some providers. There are several ways to accomplish that (REST API, Powershell and so on). I prefer using PowerShell, so I ran the following cmdlets:

It can take up to 20-25mn to register these providers. So be patient 😊

After a while run these cmdlets to check if providers are registered:

If providers are registered, run the following cmdlet to propagate change into the compute resource provider.

Create a Windows Server Azure Edition VM

Open the Azure Portal and navigate into the Marketplace. Then in search field, type Microsoft Operating System. Then in Microsoft Server Operating System Preview, click on Create and select Windows Server 2019 Datacenter: Azure Edition.

Microsoft Server Operating System Preview - Create - Windows Server 2019 Datacenter: Azure Edition.

Then specify as usual resource group, VM name, region and so on. Be sure the VM image is Windows Server 2019 Datacenter: Azure Edition – Gen2.

Microsoft Server Operating System Preview - Windows Server 2019 Datacenter: Azure Edition – Gen2

In Management view, check if Enable hotpatch (Preview) is enabled.

Microsoft Server Operating System Preview - Management - Enable hotpatch (Preview)

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Try Hotpatch

Once the VM is created, open the Azure VM and navigate in Guest + host updates | Go to Hotpatch.

Microsoft Server Operating System Preview - Guest + host updates | Go to Hotpatch

Next click on Assess now to check if the VM requires update.

Microsoft Server Operating System Preview - Guest + host updates | Go to Hotpatch - Assess now

Once the assessment is finished, click on install updates now.

Microsoft Server Operating System Preview - Guest + host updates | Go to Hotpatch - install updates now

Now you can specify the behavior of the update process such as the reboot option or the maximum duration.

Microsoft Server Operating System Preview - Guest + host updates | Go to Hotpatch - reboot option

N.B: If you wish, you can switch to updating using automation to use Azure Update Management for patching.

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Romain Serre
Romain Serre
Senior consultant at Exakis
Romain Serre works in Lyon as a Senior Consultant. He is focused on Microsoft Technology, especially on Hyper-V, System Center, Storage, networking and Cloud OS technology as Microsoft Azure or Azure Stack. He is a MVP and he is certified Microsoft Certified Solution Expert (MCSE Server Infrastructure & Private Cloud), on Hyper-V and on Microsoft Azure (Implementing a Microsoft Azure Solution).