Assigning new role to already existing user in RDS

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user-controls

database

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We have an RDS instance hosted for Aurora PostgreSQL, specifically using the 'db.r5.xlarge' instance type. When we initially set up the RDS instance, a default user named 'rdsadmin' was automatically created with the 'SUPERUSER' role.

During the setup, we also created a master user named 'X'. However, 'X' does not have 'SUPERUSER' permissions.

Our goal is to assign the 'pg_read_server_files' role to the user 'X'. The challenge we face is that we don't have the login credentials for the 'rdsadmin' user since it was a default root user provided by AWS during the RDS instance creation.

Are there any possible workarounds to assign a new role to an existing user given this situation?

What I have tried:

We attempted to use the command "GRANT pg_read_server_files to X;", but we encountered an error message: "ERROR: Cannot issue GRANT on the 'pg_read_server_files' role. Detail: Cannot GRANT on the 'pg_read_server_files' role without being a member of the role."