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.
createuser is a wrapper around the SQL command CREATE USER. There is no effective difference between creating users via this utility and via other methods for accessing the server.
createuser accepts the following command-line arguments:
Specifies the name of the PostgreSQL user to be created. This name must be unique among all PostgreSQL users.
The new user is allowed to create other users. (Note: Actually, this makes the new user a superuser. The option is poorly named.)
The new user is not allowed to create other users (i.e., the new user is a regular user, not a superuser). This is the default.
The new user is allowed to create databases.
The new user is not allowed to create databases. This is the default.
Echo the commands that createuser generates and sends to the server.
Encrypts the user's password stored in the database. If not specified, the default password behavior is used.
Allows you to pick a non-default user ID for the new user. This is not necessary, but some people like it.
Does not encrypt the user's password stored in the database. If not specified, the default password behavior is used.
If given, createuser will issue a prompt for the password of the new user. This is not necessary if you do not plan on using password authentication.
Do not display a response.
You will be prompted for a name and other missing information if it is not specified on the command line.
createuser also accepts the following command-line arguments for connection parameters:
Specifies the host name of the machine on which the server is running. If the value begins with a slash, it is used as the directory for the Unix domain socket.
Specifies the TCP port or local Unix domain socket file extension on which the server is listening for connections.
User name to connect as (not the user name to create).
Force password prompt (to connect to the server, not for the password of the new user).
In case of difficulty, see CREATE USER and psql for discussions of potential problems and error messages. The database server must be running at the targeted host. Also, any default connection settings and environment variables used by the libpq front-end library will apply.
To create a user joe on the default database server:
$ createuser joe Is the new user allowed to create databases? (y/n) n Shall the new user be allowed to create more new users? (y/n) n CREATE USER
To create the same user joe using the server on host eden, port 5000, avoiding the prompts and taking a look at the underlying command:
$ createuser -p 5000 -h eden -D -A -e joe CREATE USER "joe" NOCREATEDB NOCREATEUSER CREATE USER