This chapter describes how to create and manage roles and introduces
the privilege system. More information about the various types of
database objects and the effects of privileges can be found in
Chapter 4.
Database roles are conceptually completely separate from
operating system users. In practice it might be convenient to
maintain a correspondence, but this is not required. Database roles
are global across a database cluster installation (and not
per individual database). To create a role use the CREATE ROLE SQL command:
CREATE ROLE name;
name follows the rules for SQL
identifiers: either unadorned without special characters, or
double-quoted. (In practice, you will usually want to add additional
options, such as LOGIN, to the command. More details appear
below.) To remove an existing role, use the analogous
DROP ROLE command:
DROP ROLE name;
For convenience, the programs createuser
and dropuser are provided as wrappers
around these SQL commands that can be called from the shell command
line:
createuser name
dropuser name
To determine the set of existing roles, examine the pg_roles
system catalog, for example
SELECT rolname FROM pg_roles;
The edb-psql program's \du meta-command
is also useful for listing the existing roles.
In order to bootstrap the database system, a freshly initialized
system always contains one predefined role. This role is always
a "superuser", and by default (unless altered when running
initdb) it will have the same name as the
operating system user that initialized the database
cluster. Customarily, this role will be named
enterprisedb. In order to create more roles you
first have to connect as this initial role.
Every connection to the database server is made in the name of some
particular role, and this role determines the initial access privileges for
commands issued on that connection.
The role name to use for a particular database
connection is indicated by the client that is initiating the
connection request in an application-specific fashion. For example,
the edb-psql program uses the
-U command line option to indicate the role to
connect as. Many applications assume the name of the current
operating system user by default (including
createuser and edb-psql). Therefore it
is often convenient to maintain a naming correspondence between
roles and operating system users.
The set of database roles a given client connection may connect as
is determined by the client authentication setup, as explained in
Chapter 33. (Thus, a client is not
necessarily limited to connect as the role with the same name as
its operating system user, just as a person's login name
need not match her real name.) Since the role
identity determines the set of privileges available to a connected
client, it is important to carefully configure this when setting up
a multiuser environment.