I stopped a m5.large instance but it keeps starting back up

Hi there.

It looks like Cloud9 is managing the instance. Per the documentation:

WS Cloud9 creates an EC2 environment and a new Amazon EC2 instance, and connects the environment to this instance. AWS Cloud9 manages the lifecycle of this instance, including starting, stopping, and restarting the instance as needed. If you ever delete this environment, AWS Cloud9 automatically terminates this instance.

I haven't tried it myself, but my best guess is that you won't be able to just stop it. It looks like you will need to delete your Cloud9 environment to terminate the instance.

Alternative options (note these may not work):

• Use AWS Instance Scheduler and setup a schedule to start/stop the instance.
• If you use CodeCatalyst, you can stop the environment with the steps described in this article.

I hope this helps.