It seems that PgAdmin-III, probably, is connected via IPv6 by default, so it uses a string ident, which corresponds to an IPv6 address for localhost, ::1/128.
If you want to use password authentication, you probably want to:
host all all 127.0.0.1/32 md5
host all all ::1/128 md5
, unix, trust, , , , , . ident ( , unix , Pg) md5 ( UNIX-).
pg_hba.conf , PgAdmin-III . PgAdmin-III postgres sudo, (, , ) nano pg_hba.conf.
psql, psql , , unix, trust. , , psql, , , , .