Amazon EMR sg for Master and Core nodes

Why does Amazon EMR creates inbound rule entries for master and core security groups?

This is being implemented so that master and core/task nodes can communicate with each other in the cluster. e.g. ICMP for ping and all other ports ( which should be harmless in general ) for hadoop ports e.g. 8020, 8088 and others.

you can read more about this here -

https://docs.aws.amazon.com/emr/latest/ManagementGuide/emr-man-sec-groups.html https://docs.aws.amazon.com/emr/latest/ManagementGuide/emr-security-groups.html

it throws an exception about a circular dependency

Yes, this is expected as well. in your automation, you need to put a logic to delete the inbound rules ( as default outbound rule has 0.0.0.0/0 allow ) before deleting the security group(s).