AWS Systems Manager, Requirements and Building Blocks. The SSM Agent. AWS Systems Manager requires an agent for its management service. The Systems Manager Agent is the software required to be installed and configured on all instances in order for them to be called managed instances.

A managed instance is an instance with the ability to communicate and be operated by Systems Manager. The agent executes and process tasks you specify through any of the Systems Manager features, like the Run Command. The agent is installed by default on the Amazon Linux AMIs, the AWS Windows AMIs, and available on the Amazon Linux repo. The agent is open-sourced and available on GitHub. You can install the agent on a physical server or a virtual machine in your data center or even another cloud provider. You can manage Windows Server 2003 or later, and Linux distributions like Amazon Linux, Ubuntu, Red Hat Enterprise Linux, SUSE, and CentOS.

Managed Instance Roles. A managed instance will require an Identity and Access Management role applied as an instance profile in order for Systems Manager to be able to interact with the agent and make the instance visible in the Systems Manager Fleet Manager console. AWS provides pre-defined managed policies for Systems Manager. They usually have the acronym SSM as part of their name. One of them is called Amazon EC2 Role for SSM, which can save you time in the instance configuration. You can also create your own custom role if needed or use one of the many other SSM-related policies available. To register servers and virtual machines in your data center or other cloud providers outside the scope of Amazon EC2, you can create a hybrid activation and use the activation code and activation ID supplied to configure the agent and centrally manage your hybrid environment and EC2 instances from one location.

Fleet Manager Feature. Once you configure a managed instance, you can go to the Systems Manager console. And under the Node Management section, you will see the Fleet Manager feature. All your managed instances will be displayed in this console. Fleet Manager will give you visibility into the details of each managed instance, including Instance ID, Platform Type, Instance Type, Operating System name, IP Address, and the version of the SSM Agent that is installed among many other features. One interesting item about the Fleet Manager managed instance console is that under instance action, you can connect to the instance using the Session Manager feature of Systems Manager.

The Session Manager feature of Systems Manager is a fully-managed capability that lets you connect to any managed instance using an interactive browser shell login for Linux, Windows, and MacOS instances. It requires no open inbound ports and no need to manage bastion hosts or Secure Shell keys for connectivity to your instance. You also don't need Secure Shell clients for Linux, or Remote Desktop Protocol clients for Windows when using Session Manager. Communication between Session Manager and instances uses Transport Layer Security version 1.2, or TLS 1.2 for short. Security of the communication can be increased using your own Key Management Service keys. Session Manager tracks all commands and output produced in a session, and also provides full logging and session auditing activity that can be dispatched to CloudTrail, CloudWatch, or an Amazon S3 buckets as a result. Session Manager can control which users can access specific instances by using Identity and Access Management policies. It works through the interactive browser shell or using the AWS Command Line Interface.