PostgreSQL PG_SHADOW VIEW

PG_SHADOW is views its contains information about rolename and user password,user password validity,user connection limit and  Role automatically inherits privileges of roles it is a member of,detailed information about user and privilege management.

Name	Type	Description
usename	name	User name
usesysid	oid	ID of this user
usecreatedb	bool	User can create databases
usesuper	bool	User is a superuser
usecatupd	bool	User can update system catalogs. (Even a superuser cannot do this unless this column is true.)
passwd	text	Password (possibly encrypted); null if none. See pg_authid for details of how encrypted passwords are stored.
valuntil	abstime	Password expiry time (only used for password authentication)
useconfig	text[]	Session defaults for run-time configuration variables

Examples

--create the unencrypted user 

postgres=# create user u2 WITH UNENCRYPTED PASSWORD 'u2';
CREATE ROLE

--create the user with password validation time

postgres=# CREATE USER u3 WITH PASSWORD 'u3' VALID UNTIL '2017-06-06';
CREATE ROLE

--Describe the  PG_SHADOW view

postgres=# \d  PG_SHADOW
    View "pg_catalog.pg_shadow"
   Column    |  Type   | Modifiers 
-------------+---------+-----------
 usename     | name    | 
 usesysid    | oid     | 
 usecreatedb | boolean | 
 usesuper    | boolean | 
 usecatupd   | boolean | 
 userepl     | boolean | 
 passwd      | text    | 
 valuntil    | abstime | 
 useconfig   | text[]  | 

--list the user and show the users password and password validatation time

postgres=# select usename,usesysid,passwd,valuntil,useconfig from PG_SHADOW;
 usename  | usesysid |               passwd                |        valuntil        | useconfig 
----------+----------+-------------------------------------+------------------------+-----------
 postgres |       10 | md505ea766c2bc9e19f34b66114ace97598 |                        | 
 rep      |    24576 | md5df2c887bcb2c49b903aa33bdbc5c2984 |                        | 
 u1       |    24583 |                                     |                        | 
 u2       |    24584 | u2                                  |                        | 
 u3       |    24585 | md5dad1ef51b879799793dc38d714b97063 | 2017-06-06 00:00:00-04 | 
 nijam    |    24586 |                                     |                        | 
(6 rows)