I don't know why postgres is prompting for a password. But you could try putting the following in your crontab:
su postgres -c 'pg_dump ...' Simon 2011/3/24 Jaroslav Záruba <jaroslav.zar...@gmail.com> > Hello > > I have pg_dump command in cron that accesses PostgreSQL under user postgres > and does not provide a password. > > pg_dump --username=postgres ... > > I have set in pg_hba.conf that user postgres should be trusted for all > databases from localhost. > > local all postgres trust > > When I run the command under regular user it works. > When I run it under root (sudo -i) it requires password, and therefore the > crontab task fails to authenticate. > > (I'm looking at both users' 'export' command output, and there seems to be > nothing related to PostgreSQL.) > > Could someone explain to me what is happening here? > > Regards > J. Záruba