Are PostgreSQL roles always associated with a Linux user account? In other
words, can I have a PostgresSQL user account that is unrelated to any Linux
account? Is there a detailed tutorial on accounts and roles that explains
this topic? I found the following confusing:
http://www.postgresql.org/docs/9.3/static/client-authentication.html
http://www.postgresql.org/docs/9.3/static/user-manag.html
http://www.postgresql.org/docs/9.3/static/database-roles.html