PostgreSQL User Creation Using Utility

• createuser creates a new PostgreSQL user. Only superusers (users with usesuper set in the pg_shadow table) can create new PostgreSQL users, so createuser must be invoked by someone who can connect as a PostgreSQL superuser.
• Being a superuser also implies the ability to bypass access permission checks within the database, so superuserdom should not be granted lightly.

SYNTAX:

createuser [option...] [username]

WHEN you create user on command line mode The database server must be running at the targeted host

— Creating u5 user using createuser utility

[root@p1 bin]# cd /opt/PostgreSQL/9.3/bin/
[root@p1 bin]# ./createuser u5
Password: 

postgres=# select usename,passwd,valuntil,usecreatedb from PG_SHADOW;
 usename  |               passwd                |        valuntil        | usecreatedb 
----------+-------------------------------------+------------------------+-------------
 postgres | md505ea766c2bc9e19f34b66114ace97598 |                        | t
 rep      | md5df2c887bcb2c49b903aa33bdbc5c2984 |                        | f
 u1       |                                     |                        | f
 u2       | u2                                  |                        | f
 u3       | md5dad1ef51b879799793dc38d714b97063 | 2017-06-06 00:00:00-04 | f
 nijam    |                                     |                        | f
 u4       | md54af10c3137cf79c12265e8d288070711 |                        | t
 u5       |                                     |                        | f
(8 rows)

— To create the  user u7 using the server on host p1, port 5432, avoiding the prompts and taking a look at the underlying command:

-bash-3.2$ hostname
p1

-bash-3.2$ ./createuser -h p1 -p 5432 -D -A -e u7
Password: 
CREATE ROLE u7 NOSUPERUSER NOCREATEDB NOCREATEROLE INHERIT LOGIN;

—  Check the user u7 whether successfully created or not

postgres=# \du 
                             List of roles
 Role name |                   Attributes                   | Member of 
-----------+------------------------------------------------+-----------
 nijam     |                                                | {}
 postgres  | Superuser, Create role, Create DB, Replication | {}
 rep       | Replication                                   +| {}
           | 1 connection                                   | 
 u1        |                                                | {}
 u2        |                                                | {}
 u3        | Password valid until 2017-06-06 00:00:00-04    | {}
 u4        | Create DB                                      | {}
 u5        |                                                | {}
 u6        |                                                | {}
 u7        |                                                | {}

postgres=# select usename,passwd,valuntil,usecreatedb from PG_SHADOW;                          
 usename  |               passwd                |        valuntil        | usecreatedb 
----------+-------------------------------------+------------------------+-------------
 postgres | md505ea766c2bc9e19f34b66114ace97598 |                        | t
 rep      | md5df2c887bcb2c49b903aa33bdbc5c2984 |                        | f
 u1       |                                     |                        | f
 u2       | u2                                  |                        | f
 u3       | md5dad1ef51b879799793dc38d714b97063 | 2017-06-06 00:00:00-04 | f
 nijam    |                                     |                        | f
 u4       | md54af10c3137cf79c12265e8d288070711 |                        | t
 u5       |                                     |                        | f
 u6       |                                     |                        | f
 u7       |                                     |                        | f
(10 rows)

— To create the user joe as a superuser, and assign a password immediately:

-bash-3.2$ ./createuser -P -d -a -e u8
Enter password for new role: 
Enter it again: 
Password: 
CREATE ROLE u8 PASSWORD 'md5b9f930ae0484417a1883fd3f7cdb490e' SUPERUSER CREATEDB CREATEROLE INHERIT LOGIN;

Note: when issuing the above utility you will get password prompt first prompt is u8 user password, second one is u8 user password confirmation and third prompt is super user password .

— let us check the new user roles and privileges whether u8 user having  above mentioned privilege

postgres=# \du                                                       
                             List of roles
 Role name |                   Attributes                   | Member of 
-----------+------------------------------------------------+-----------
 nijam     |                                                | {}
 postgres  | Superuser, Create role, Create DB, Replication | {}
 rep       | Replication                                   +| {}
           | 1 connection                                   | 
 u1        |                                                | {}
 u2        |                                                | {}
 u3        | Password valid until 2017-06-06 00:00:00-04    | {}
 u4        | Create DB                                      | {}
 u5        |                                                | {}
 u6        |                                                | {}
 u7        |                                                | {}
 u8        | Superuser, Create role, Create DB              | {}