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Configure EC2 instances
In the Configure EC2 Instances screen, you'll need to select an Instance Type for your Master and Core Instance groups. Amazon's "m1.large" instance type is the minimum required for an EMR cluster. If you're creating a cluster just for learning purposes, this will be your least expensive and therefore most sensible option. Select it for both the Master Instance Group and Core Instance Group.
With your instance types selected, you now need to set the number of instances in your Core and Task Instance groups. Again, if you're just putting up a cluster for learning purposes, you will want to minimize the resources you're using, so change the Core Instance Group's Instance Count from the default setting of 2 to just 1. Leave the same setting for the Task Instance Group at 0, and click Continue.
When you provisioned your AWS account, you should have created at least one EC2 key pair. Pick one for your EMR cluster. Without it, you won't be able to establish a secure terminal session and work interactively with Hadoop. Once you've selected a key pair, click Continue.