An SSM Agent is software installed on Amazon Elastic Compute Cloud (EC2) instances and other supported machine types, designed to allow AWS Systems Manager to update, manage, and configure them. It acts as the local interface for the AWS Systems Manager service, enabling the execution of remote commands and scripts.
Core Functionality of the SSM Agent
The primary role of the SSM Agent is to process requests from the AWS Systems Manager service, ensuring that instances are configured as specified. When a command is initiated via Systems Manager, the agent running on the target instance receives the instruction, processes the associated SSM document (a JSON or YAML file that defines actions), and then carries out the specified tasks.
Key functions and capabilities enabled by the SSM Agent include:
- Remote Command Execution: Run scripts, shell commands, and PowerShell commands on one or more instances.
- Patch Management: Apply operating system and software patches automatically across a fleet of instances.
- Software Inventory: Collect information about applications, files, network configurations, and system properties.
- State Management: Define and maintain a consistent state for your server configurations.
- Instance Automation: Automate common administrative tasks like starting/stopping services, installing updates, or joining a domain.
- Session Manager: Provide interactive one-click browser-based access to instances, eliminating the need for SSH keys or bastion hosts.
How the SSM Agent Works
The SSM Agent maintains a constant connection with the AWS Systems Manager service. When an administrator or an automated process sends a command through Systems Manager, the agent on the target instance:
- Receives the Command: Listens for and receives instructions from the Systems Manager service.
- Downloads the SSM Document: Accesses the relevant SSM document, which outlines the actions to be performed.
- Executes Instructions: Processes the document, translating the defined steps into actions on the instance, such as running a script, installing software, or changing a configuration.
- Reports Status: Sends execution status and output back to the Systems Manager service, providing visibility into the command's success or failure.
Benefits of Using the SSM Agent
Implementing the SSM Agent offers several operational advantages for managing compute instances:
| Benefit | Description |
|---|---|
| Centralized Management | Manage a large fleet of instances from a single console or API, regardless of their location (AWS EC2, on-premises, or other clouds). |
| Automation & Efficiency | Automate routine tasks, reducing manual effort and potential for human error. |
| Security & Compliance | Enforce security policies, apply patches, and maintain desired configurations to meet compliance requirements without opening inbound ports. |
| Reduced Operational Burden | Streamline operations, eliminate the need for traditional remote access tools (like SSH or RDP for some tasks), and simplify troubleshooting. |
| Visibility | Gain insights into instance configurations, software inventory, and operational status. |
Where to Find More Information
For technical details, installation instructions, and the open-source code, you can refer to the official Amazon SSM Agent GitHub repository.
