# Amazon Systems Manager reference
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The following information and topics can help you better implement Amazon Systems Manager solutions.

**Principal**  
In Amazon Identity and Access Management (IAM), you can grant or deny a service access to resources using the Principal policy element. The Principal policy element value for Systems Manager is `ssm.amazonaws.com.cn`.

 **Supported Amazon Web Services Regions and endpoints **  
See [Systems Manager service endpoints](https://docs.amazonaws.cn/general/latest/gr/ssm.html#ssm_region) in the *Amazon Web Services General Reference*.

 **Service Quotas**  
See [Systems Manager service quotas](https://docs.amazonaws.cn/general/latest/gr/ssm.html#limits_ssm) in the *Amazon Web Services General Reference*.

 **API Reference**  
See *[Amazon Systems Manager API Reference](https://docs.amazonaws.cn/systems-manager/latest/APIReference/)*.

 **Amazon CLI Command Reference**  
See [Amazon Systems Manager section of the Amazon CLI Command Reference](https://docs.amazonaws.cn/cli/latest/reference/ssm/index.html).

 **Amazon Tools for PowerShell Cmdlet Reference**  
See [Amazon Systems Manager section of the Amazon Tools for PowerShell Cmdlet Reference](https://docs.amazonaws.cn/powershell/latest/reference/items/AWS_Systems_Manager_cmdlets.html).

 **SSM Agent Repository on GitHub**  
See [aws/amazon-ssm-agent](https://github.com/aws/amazon-ssm-agent).

 **Ask a Question**  
[Amazon Systems Manager Developer Forum](https://forums.aws.csdn.net/)

**Topics**
+ [Using this service with an Amazon SDK](sdk-general-information-section.md)
+ [Reference: Amazon S3 buckets for patching operations](patch-operations-s3-buckets.md)
+ [Reference: Amazon EventBridge event patterns and types for Systems Manager](reference-eventbridge-events.md)
+ [Reference: Cron and rate expressions for Systems Manager](reference-cron-and-rate-expressions.md)
+ [Reference: ec2messages, ssmmessages, and other API operations](systems-manager-setting-up-messageAPIs.md)
+ [Reference: Date and time string formats for Systems Manager](systems-manager-datetime-strings.md)