# AMS Accelerate patch baseline
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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.

## Default patch baseline
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When you onboard to AMS Accelerate patching, the default patch baselines are overridden by the AMS Accelerate default patch baselines for the following operating systems.
+ **Windows**
+ **Amazon Linux 1**
+ **Amazon Linux 2**
+ **CentOS**
+ **Suse**
+ **Rhel**
+ **Ubuntu**

**Important**  
 Default patch baselines are managed by AMS. Do not edit default patch baselines as your changes may be lost. Instead, create a custom patch baseline. See [Custom patch baseline with AMS Accelerate](acc-patch-baseline-custom.md) 

**Note**  
The AMS Accelerate patch baselines defined as **product = \$1** mean that all patches are applied to the instance of all security and classifications.

# Custom patch baseline with AMS Accelerate
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To use a custom patch baseline with AMS Accelerate, first make sure that you have a patch group, and then create the custom baseline.

For more information, see the following resources:
+  [ Working with patch groups](https://docs.aws.amazon.com/systems-manager/latest/userguide/sysman-patch-group-tagging.html) 
+  [ Creating a custom patch baseline (Windows)](https://docs.aws.amazon.com/systems-manager/latest/userguide/create-baseline-console-windows.html) 
+  [ Creating a custom patch baseline (Linux)](https://docs.aws.amazon.com/systems-manager/latest/userguide/create-baseline-console-linux.html) 
+  [ Updating or deleting a custom patch baseline (console)](https://docs.aws.amazon.com/systems-manager/latest/userguide/patch-baseline-update-or-delete.html)