Add List Database Users as a postgres til.

postgres/list-database-users.md

@@ -0,0 +1,13 @@
+# List Database Users
+
+Within `psql`, type `\du` to list all the users for a database and their
+respective permissions.
+
+```bash
+> \du
+                              List of roles
+ Role name  |                   Attributes                   | Member of
+------------+------------------------------------------------+-----------
+ jbranchaud | Superuser, Create role, Create DB, Replication | {}
+ sampleuser | Create DB                                      | {}
+ ```