Associate a Role to a running AWS instance

Question

In order to run AWS monitoring scripts (http://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/mon-scripts-perl.html) on one of my ec2 existing instance, I need a IAM

Answer 1

If not, what can I do? Launch a new instance with a role and transfert the volumes to it?

This is one option but it might take you a long time if you have a lot instances.

The other option is to simply use IAM by creating a new user then add the Amazon CloudWatch PutMetricData operation permission to that user. Then, create AWS credentials for that user and finally use them as per the docs that you specified:

Optional: If you aren't using an IAM role, update the awscreds.template file that you downloaded earlier. The content of this file should use the following format:

AWSAccessKeyId=YourAccessKeyID

AWSSecretKey=YourSecretAccessKey

Also set the environment variable AWS_CREDENTIAL_FILE to point that awscreds.template in the environment of the user that is running the mon-scripts-perl