AWS Systems Manager
User Guide

Verify Default Patch Baselines or Create a Custom Patch Baseline

A patch baseline defines which patches are approved for installation on your instances. You can specify approved or rejected patches one by one. You can also create auto-approval rules to specify that certain types of updates (for example, critical updates) should be automatically approved. The rejected list overrides both the rules and the approve list.

To use a list of approved patches to install specific packages, you first remove all auto-approval rules. If you explicitly identify a patch as rejected, it will not be approved or installed, even if it matches all of the criteria in an auto-approval rule. Also, a patch is installed on an instance only if it applies to the software on the instance, even if the patch has otherwise been approved for the instance.

Pre-Defined vs. Custom Baselines

Patch Manager provides pre-defined patch baselines for each of the operating systems supported by Patch Manager. You can use these baselines as they are currently configured (you can't customize them) or you can create your own patch baselines if you want greater control over which patches are approved or rejected for your environment.

Pre-Defined Baselines

The following table describes the pre-defined patch baselines provided with Patch Manager.

Name Supported Products Details


Windows (Windows Server 2008 – 2016)

Approves all operating system patches with a classification of "CriticalUpdates" or "SecurityUpdates" and an MSRC severity of "Critical" or "Important" seven days after release.


Amazon Linux (2012.03 – 2017.09)

Approves all operating system patches with a classification of "Security" and severity of "Critical" or "Important" seven days after release. Also approves all patches with a classification of "Bugfix" seven days after release


Ubuntu Server (14.04/16.04)

Immediately approves all operating system security-related patches with a priority of "Required" or "Important". There is no wait before approval because reliable release dates are not available in the repos.


Redhat Enterprise LinuxRed Hat Enterprise Linux (6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3)

Approves all operating system patches with a classification of "Security" and severity of "Critical" or "Important" seven days after release. Also approves all patches with a classification of "Bugfix" seven days after release.

AWS-SuseDefaultPatchBaseline SUSE Linux Enterprise Server 12 Approves all operating system patches with a classification of "Security" and a severity of "Critical" or "Important" seven days after release.

Custom Baselines

If you create your own patch baseline, you can choose which patches to auto-approve by using the following categories.

  • Operating system: Windows, Amazon Linux, Ubuntu Server, etc.

  • Product name: For example, RHEL 6.5, Amazon Linux 2014.09, Windows Server 2012, Windows Server 2012 R2, etc.

  • Classification: For example, critical updates, security updates, etc.

  • Severity: For example, critical, important, etc.

For each auto-approval rule that you create, you can specify an auto-approval delay. This delay is the number of days to wait after the patch was released, before the patch is automatically approved for patching. For example, if you create a rule using the Critical Updates classification and configure it for seven days auto-approval delay, then a new critical patch released on January 7 will automatically be approved on January 14.


If a Linux repository doesn’t provide release date information for packages, Systems Manager treats the Auto Approval Delay as having a value of zero.

You can also specify a compliance severity level. If an approved patch is reported as missing, Compliance Level is the severity of the compliance violation.

By using multiple patch baselines with different auto-approval delays, you can deploy patches at different rates to different instances. For example, you can create separate patch baselines and auto-approval delays for development and production environments. This enables you to test patches in your development environment before they get deployed in your production environment.

Keep the following in mind when you create a patch baseline:

  • Patch Manager provides a default patch baseline for each supported operating system. You can instead create your own patch baseline and designate that as the default patch baseline for the corresponding operating system.

  • For on-premises or non-Amazon EC2 instances, Patch Manager attempts to use your custom default patch baseline. If no custom default patch baseline exists, the system uses the pre-defined patch baseline for the corresponding operating system.

  • If a patch is listed as both approved and rejected in the same patch baseline, the patch is rejected.

  • An instance can have only one patch baseline defined for it.

  • When you create patch baselines for Amazon Linux and RHEL, if you specify Approved Patches, be aware that Systems Manager supports Bugzilla ID, CVE ID, Advisory ID, and package-name wildcards. If you specify Rejected Patches, Systems Manager only supports package-name wildcards. For Ubuntu Server baselines, only full package names are supported in both the Approved and Rejected Patches fields.

To view an example of how to create a patch baseline by using the Systems Manager console or the AWS CLI, see Systems Manager Patch Manager Walkthroughs.

Important Differences Between Windows and Linux Patching

The following table describes important differences between Windows and Linux patching.


To patch Linux instances, your instances must be running SSM Agent version 2.0.834.0 or later. For information about updating the agent, see the section titled Example: Update the SSM Agent in Executing Commands from the Console.

The AWS-ApplyPatchBaseline SSM document doesn't support Linux instances. For applying patch baselines to both Windows and Linux instances, the recommended SSM document is AWS-RunPatchBaseline. For more information, see Overview of SSM Documents for Patching Instances and About the SSM Document AWS-RunPatchBaseline.

Difference Details

Patch evaluation

Patch Manager uses a different process to evaluate which patches should be present on Windows managed instances versus Linux managed instance. 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).

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

Not Applicable patches

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