Understanding PostgreSQL roles and permissions - Amazon Relational Database Service
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Understanding PostgreSQL roles and permissions

When you create an RDS for PostgreSQL DB instance using the Amazon Web Services Management Console, an administrator account is created at the same time. By default, its name is postgres, as shown in the following screenshot:

The default login identity for Credentials in the Create database page is postgres.

You can choose another name rather than accept the default (postgres). If you do, the name you choose must start with a letter and be between 1 and 16 alphanumeric characters. For simplicity's sake, we refer to this main user account by its default value (postgres) throughout this guide.

If you use the create-db-instance Amazon CLI rather than the Amazon Web Services Management Console, you create the name by passing it with the master-username parameter in the command. For more information, see Creating an Amazon RDS DB instance.

Whether you use the Amazon Web Services Management Console, the Amazon CLI, or the Amazon RDS API, and whether you use the default postgres name or choose a different name, this first database user account is a member of the rds_superuser group and has rds_superuser privileges.