Key differences between Linux and Windows patching

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

Note

To patch Linux managed nodes, your nodes must be running SSM Agent version 2.0.834.0 or later.

An updated version of SSM Agent is released whenever new capabilities are added to Systems Manager or updates are made to existing capabilities. Failing to use the latest version of the agent can prevent your managed node from using various Systems Manager capabilities and features. For that reason, we recommend that you automate the process of keeping SSM Agent up to date on your machines. For information, see Automating updates to SSM Agent. Subscribe to the SSM Agent Release Notes page on GitHub to get notifications about SSM Agent updates.

Difference 1: Patch evaluation

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

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