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Key differences between patching Linux nodes and Windows Server nodes

This topic describes important differences between Linux and Windows Server patching in Patch Manager, a capability of Amazon Systems Manager.

Difference 1: Patch evaluation

Patch Manager uses different processes on Windows managed nodes and Linux managed nodes in order to evaluate which patches should be present.

Linux

For Linux patching, Systems Manager evaluates patch baseline rules and the list of approved and rejected patches on each managed node. Systems Manager must evaluate patching on each node because the service retrieves the list of known patches and updates from the repositories that are configured on the managed node.

Windows

For Windows patching, Systems Manager evaluates patch baseline rules and the list of approved and rejected patches directly in the service. It can do this because Windows patches are pulled from a single repository (Windows Update).

Difference 2: Not Applicable patches>

Due to the large number of available packages for Linux operating systems, Systems Manager doesn't report details about patches in the Not Applicable state. A Not Applicable patch is, for example, a patch for Apache software when the instance doesn't have Apache installed. Systems Manager does report the number of Not Applicable patches in the summary, but if you call the DescribeInstancePatches API for a managed node, the returned data doesn't include patches with a state of Not Applicable. This behavior is different from Windows.

Difference 3: SSM document support

The AWS-ApplyPatchBaseline Systems Manager document (SSM document) doesn't support Linux managed nodes. For applying patch baselines to Linux, macOS, and Windows Server managed nodes, the recommended SSM document is AWS-RunPatchBaseline. For more information, see About SSM documents for patching managed nodes and About the AWS-RunPatchBaseline SSM document.

Difference 4: Application patches

The primary focus of Patch Manager is applying patches to operating systems. However, you can also use Patch Manager to apply patches to some applications on your managed nodes.

Linux

On Linux operating systems, Patch Manager uses the configured repositories for updates, and doesn't differentiate between operating systems and application patches. You can use Patch Manager to define which repositories to fetch updates from. For more information, see How to specify an alternative patch source repository (Linux).

Windows

On Windows Server managed nodes, you can apply approval rules, as well as Approved and Rejected patch exceptions, for applications released by Microsoft, such as Microsoft Word 2016 and Microsoft Exchange Server 2016. For more information, see Working with custom patch baselines.

Difference 5: Rejected patch list options in custom patch baselines

When you create a custom patch baseline, you can specify one or more patches for a Rejected patches list. For Linux managed nodes, you can also choose to allow them to be installed if they're dependencies for another patch allowed by the baseline.

Windows Server, however, doesn't support the concept of patch dependencies. You can add a patch to the Rejected patches list in a custom baseline for Windows Server, but the result depends on (1) whether or not the rejected patch is already installed on a managed node, and (2) which option you choose for Rejected patches action.

Refer to the following table for details about rejected patch options on Windows Server.

Each patch for Windows Server that Microsoft releases typically contains all the information needed for the installation to succeed. Occasionally, however, a prerequisite package might be required, which you must install manually. Patch Manager doesn't report information about these prerequisites. For related information, see Windows Update issues troubleshooting on the Microsoft website.