Authenticating user `postgres'

Hello:

I have a pg_hba.conf question.  Currently the authentication is setup
as thus:

local   db1       password        passwd.db1
local   db2       password        passwd.db2
local   all       password        passwd.su

So, I store passwords for users in separate files for each database.
The third line is for the internal postgres templates.

The problem I'm having is that I want local UNIX user `postgres', who
is the database superuser, to be able to connect to any database
without a password.  I want, for example, to be able to run a cronjob
like "pg_dumpall >backup", but I can't do that with my current setup.

Any ideas?

Many thanks,
--
Arcady Genkin
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