If you have the AMI in your AWS deployment, then you can attach an EC2 role to your AMI. Here are the steps to accomplish this:
1) Create the Splunk Policy using this documentation: http://docs.splunk.com/Documentation/AddOns/released/AWS/ConfigureAWSpermissions Call it "SplunkPolicy"
2) Open IAM-> Click on Roles -> click on Create Role -> (Under AWS Service) click on EC2 then click on Next:Permissions
3) Search for your SplunkPolicy that you just created and select it using the checkbox; and click "Next:Review"
4) Name the role, "SplunkEC2Role" and click Create Role
5) Under the EC2 Instances dashboard, click on the Instances link.
6) Select your instance, then click Actions -> Instance Settings -> Attach/Replace IAM role and select the EC2 policy you just created.
This will allow the Add-on to auto discover the policy and you should be able to use this role to start collecting data.
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