From CKAN

These are the default Postgres 8.4 permissions settings (/etc/postgresql/8.4/main/pg_hba.conf):

# Database administrative login by UNIX sockets
local   all         postgres                          ident 

# TYPE  DATABASE    USER        CIDR-ADDRESS          METHOD 

# "local" is for Unix domain socket connections only
local   all         all                            ident
# IPv4 local connections:
host    all         all         127.0.0.1/32          md5 
# IPv6 local connections:
host    all         all         ::1/128               md5 

Therefore:

• if you do 'psql -l' then it does a local connection, which uses 'ident' auth, meaning your unix username is your user. You can set the user like this: 'sudo -u postgres psql -l'. But this only works for the superuser and users setup to have the same name as linux users.
• if you do 'psql -h localhost -U postgres -l' then it uses the md5 and you supply the postgres user password (which you will have needed to set).

Superuser account

(See /etc/postgresql/8.4/main/pg_hba.conf)

• This is the only account by default when you install Postgres
• Can be accessed by using 'sudo -u postgres' before the command
• You can also set a password (but of no use with default ident authentication)

$ sudo -u postgres psql postgres
postgres=# \password
$ psql -U postgres -l