aws rds describe-db-engine-versions --output text

See also

• AWS RDS: AWS::RDS, aws rds [ create-db-instance | create-db-instance-read-replica | describe-db-instances | modify-db-instance | modify-db-cluster | create-db-subnet-group | delete-db-instance | create-db-snapshot | aws rds create-db-parameter-group ], AllocatedStorage, FreeStorageSpace