AWS Systems Manager Session Manager for Shell Access to EC2 Instances

The new Session Manager makes the AWS Systems Manager even more powerful. You can now use a new browser-based interactive shell and a command-line interface (CLI) to manage your Windows and Linux instances. Here’s what you get:

Secure Access – You don’t have to manually set up user accounts, passwords, or SSH keys on the instances and you don’t have to open up any inbound ports. Session Manager communicates with the instances via the SSM Agent across an encrypted tunnel that originates on the instance, and does not require a bastion host.

Access Control – You use IAM policies and users to control access to your instances, and don’t need to distribute SSH keys. You can limit access to a desired time/maintenance window by using IAM’s Date Condition Operators.

Auditability – Commands and responses can be logged to Amazon CloudWatch and to an S3 bucket. You can arrange to receive an SNS notification when a new session is started.

Interactivity – Commands are executed synchronously in a full interactive bash (Linux) or PowerShell (Windows) environment

Programming and Scripting – In addition to the console access that I will show you in a moment, you can also initiate sessions from the command line (aws ssm ...) or via the Session Manager APIs.

The SSM Agent running on the EC2 instances must be able to connect to Session Manager’s public endpoint. You can also set up a PrivateLink connection to allow instances running in private VPCs (without Internet access or a public IP address) to connect to Session Manager.

Session Manager in Action
In order to use Session Manager to access my EC2 instances, the instances must be running the latest version (2.3.12 or above) of the SSM Agent. The instance role for the instances must reference a policy that allows access to the appropriate services; you can create your own or use AmazonEC2RoleForSSM. Here are my EC2 instances (sk1 and sk2 are running Amazon Linux; sk3-win and sk4-win are running Microsoft Windows):

Before I run my first command, I open AWS Systems Manager and click Preferences. Since I want to log my commands, I enter the name of my S3 bucket and my CloudWatch log group. If I enter either or both values, the instance policy must also grant access to them: