I have a postgresql 8.3 db set up on linux box, together with a user postgres The pg_hba.conf reads
local all postgres ident
You have to change both lines for IPv4 and IPv6 in pg_hba.conf
# IPv4 local connections: host all all 127.0.0.1/32 md5 # IPv6 local connections: host all all ::1/128 md5
Server restart is needed.