TargetNotConnected when opening a SSM session on EC2

Question

Hi all,
I'm a beginner and I apologize for the silly question. I have two EC2 instances on the same availability zone, to which I attached the same IAM role containing the policy AmazonSSMManagedInstanceCore. This policy should allow working with SSM.
While I can start and open a session for tunnel forwarding via AWS CLI with the first instance, I cannot do the same for the second one, and I don't understand why.
When I start the first instance, I see it under the target instances in the session manager. If I do it for the second one, this isn't the case.
I went through this -> https://docs.aws.amazon.com/systems-manager/latest/userguide/session-manager-troubleshooting.html#ssh-target-not-connected, but I couldn't solve the issue.
It might be a simple solution, but I cannot see it without help.
Regards

AP.

Answer

could you please check if SSM agent is installed. I am not sure which OS you are using. Hence here is the link that might help https://docs.aws.amazon.com/systems-manager/latest/userguide/ssm-agent.html

Answer

Hi!

If one instance works and the other doesn't, could you check the following:

* Are both instances started from the same OS (and from the same Amazon Machine Image)?
* Do they both have similar configuration, specifically the instance profile (IAM) for the ec2 instances?
* Is the SSM Agent installed on the troublesome EC2 instance?
* Do the instances have the proper outbound connectivity?  (Outbound to some AWS services including ec2messages.region.amazonaws.com, ssm.region.amazonaws.com, ssmmessages.region.amazonaws.com)

Check out the prerequisites here: https://docs.aws.amazon.com/systems-manager/latest/userguide/session-manager-prerequisites.html

TargetNotConnected when opening a SSM session on EC2

Relevant content