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><A
NAME="DATABASE-ROLES"
>20.1. Database Roles</A
></H1
><P
> 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 <A
HREF="sql-createrole.html"
>CREATE ROLE</A
> SQL command:
</P><PRE
CLASS="SYNOPSIS"
>CREATE ROLE <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>;</PRE
><P>
<TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> 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 <TT
CLASS="LITERAL"
>LOGIN</TT
>, to the command. More details appear
below.) To remove an existing role, use the analogous
<A
HREF="sql-droprole.html"
>DROP ROLE</A
> command:
</P><PRE
CLASS="SYNOPSIS"
>DROP ROLE <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>;</PRE
><P>
</P
><P
> For convenience, the programs <A
HREF="app-createuser.html"
><SPAN
CLASS="APPLICATION"
>createuser</SPAN
></A
>
and <A
HREF="app-dropuser.html"
><SPAN
CLASS="APPLICATION"
>dropuser</SPAN
></A
> are provided as wrappers
around these SQL commands that can be called from the shell command
line:
</P><PRE
CLASS="SYNOPSIS"
>createuser <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>
dropuser <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
></PRE
><P>
</P
><P
> To determine the set of existing roles, examine the <TT
CLASS="STRUCTNAME"
>pg_roles</TT
>
system catalog, for example
</P><PRE
CLASS="SYNOPSIS"
>SELECT rolname FROM pg_roles;</PRE
><P>
The <A
HREF="app-psql.html"
><SPAN
CLASS="APPLICATION"
>psql</SPAN
></A
> program's <TT
CLASS="LITERAL"
>\du</TT
> meta-command
is also useful for listing the existing roles.
</P
><P
> In order to bootstrap the database system, a freshly initialized
system always contains one predefined role. This role is always
a <SPAN
CLASS="QUOTE"
>"superuser"</SPAN
>, and by default (unless altered when running
<TT
CLASS="COMMAND"
>initdb</TT
>) it will have the same name as the
operating system user that initialized the database
cluster. Customarily, this role will be named
<TT
CLASS="LITERAL"
>postgres</TT
>. In order to create more roles you
first have to connect as this initial role.
</P
><P
> Every connection to the database server is made using the name of some
particular role, and this role determines the initial access privileges for
commands issued in 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 <TT
CLASS="COMMAND"
>psql</TT
> program uses the
<TT
CLASS="OPTION"
>-U</TT
> command line option to indicate the role to
connect as. Many applications assume the name of the current
operating system user by default (including
<TT
CLASS="COMMAND"
>createuser</TT
> and <TT
CLASS="COMMAND"
>psql</TT
>). Therefore it
is often convenient to maintain a naming correspondence between
roles and operating system users.
</P
><P
> The set of database roles a given client connection can connect as
is determined by the client authentication setup, as explained in
<A
HREF="client-authentication.html"
>Chapter 19</A
>. (Thus, a client is not
limited to connect as the role matching
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 privileges when setting up
a multiuser environment.
</P
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