Amazon Redshift clusters should not use the default Admin username

How to fix it

• Replaces the resource: The admin user name is fixed at creation and a snapshot restore keeps it, so create a new cluster, move the data with UNLOAD and COPY, repoint clients, then delete this one.

In the console

Redshift → Create cluster → Database configurations → Admin user name, which is fixed once the cluster exists

Admin user name

On a new cluster, a name other than awsuser, admin, root, sa, oracle or postgres

With Terraform

• Can't be undone: Changing master_username on the existing cluster's resource makes Terraform plan to destroy it and create an empty one, so declare the new cluster as a separate resource.

resource "aws_redshift_cluster" "this" {
  cluster_identifier = var.cluster_identifier
  node_type          = var.node_type
  master_username    = var.master_username
}