PostgreSQL 9.2.3 Documentation
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# 20.2. Role Attributes

A database role can have a number of attributes that define its privileges and interact with the client authentication system.

login privilege

  Only roles that have the `LOGIN` attribute can be used as the initial role name for a database connection. A role with the `LOGIN` attribute can be considered the same as a "database user". To create a role with login privilege, use either:

      CREATE ROLE name LOGIN;
      CREATE USER name;

  (`CREATE USER` is equivalent to `CREATE ROLE` except that `CREATE USER` assumes `LOGIN` by default, while `CREATE ROLE` does not.)

superuser status

  A database superuser bypasses all permission checks, except the right to log in. This is a dangerous privilege and should not be used carelessly; it is best to do most of your work as a role that is not a superuser. To create a new database superuser, use `CREATE ROLE `name` SUPERUSER`. You must do this as a role that is already a superuser.

database creation

  A role must be explicitly given permission to create databases (except for superusers, since those bypass all permission checks). To create such a role, use `CREATE ROLE `name` CREATEDB`.

role creation

  A role must be explicitly given permission to create more roles (except for superusers, since those bypass all permission checks). To create such a role, use `CREATE ROLE `name` CREATEROLE`. A role with `CREATEROLE` privilege can alter and drop other roles, too, as well as grant or revoke membership in them. However, to create, alter, drop, or change membership of a superuser role, superuser status is required; `CREATEROLE` is insufficient for that.

initiating replication

  A role must explicitly be given permission to initiate streaming replication (except for superusers, since those bypass all permission checks). A role used for streaming replication must always have `LOGIN` permission as well. To create such a role, use `CREATE ROLE `name` REPLICATION LOGIN`.

password

  A password is only significant if the client authentication method requires the user to supply a password when connecting to the database. The `password` and `md5` authentication methods make use of passwords. Database passwords are separate from operating system passwords. Specify a password upon role creation with `CREATE ROLE `name` PASSWORD '`string`'`.

A role's attributes can be modified after creation with `ALTER ROLE`. See the reference pages for the CREATE ROLE and ALTER ROLE commands for details.

> Tip: It is good practice to create a role that has the `CREATEDB` and `CREATEROLE` privileges, but is not a superuser, and then use this role for all routine management of databases and roles. This approach avoids the dangers of operating as a superuser for tasks that do not really require it.

A role can also have role-specific defaults for many of the run-time configuration settings described in Chapter 18. For example, if for some reason you want to disable index scans (hint: not a good idea) anytime you connect, you can use:

    ALTER ROLE myname SET enable_indexscan TO off;

This will save the setting (but not set it immediately). In subsequent connections by this role it will appear as though `SET enable_indexscan TO off` had been executed just before the session started. You can still alter this setting during the session; it will only be the default. To remove a role-specific default setting, use `ALTER ROLE `rolename` RESET `varname``. Note that role-specific defaults attached to roles without `LOGIN` privilege are fairly useless, since they will never be invoked.

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