unattended rdiff-backup

[Michael S. Koenig]

On RedHat 7.3 w/uname -a 

Linux www.theanswergroup.com 2.4.18-5 #1 Mon Jun 10 15:14:29 EDT 2002 i586 
unknown

I seem to have things configured OK, but I cannot get rdiff-backup to run
from cron.  (It works fine from a command prompt.  I am running it on
RedHat Linux 7.3 on both local and remote.  Python 2.2 installed and
working.  SSH and Keychain installed and working.  /root/.ssh/config set
up and working.  rdiff-backup installed in /usr/bin and in path of root
for cron job on local and remote.  ypservices look OK, and so does
/etc/hosts.allow and /var/yp/securenets.  The following command runs fine
from a shell prompt:

rdiff-backup primary-backup::/home/skoenig /data/backup/sue

but does not work from cron.  I get the following error:

>From root@mike.theanswergroup.com Fri Aug 30 11:42:12 2002
Date: Fri, 30 Aug 2002 11:40:04 -0400
From: Cron Daemon <root@mike.theanswergroup.com>
To: root@mike.theanswergroup.com
Subject: Cron <root@mike> rdiff-backup primary-backup::/home/skoenig
    /data/backup/sue

Permission denied, please try again.
Permission denied, please try again.
Permission denied (publickey,password,keyboard-interactive).
Fatal Error: Truncated header string (problem probably originated 
remotely)

Couldn't start up the remote connection by executing

    ssh -C primary-backup rdiff-backup --server

Remember that, under the default settings, rdiff-backup must be
installed in the PATH on the remote system.  See the man page for more
information.

I get this entry in /var/log/messages on the remote host:

Aug 30 11:57:03 www ypserv[7011]: refused connect from 192.168.50.1:34261 
to procedure ypproc_match

I added a line:

servername,root,domain_name to /etc/netgroup

to no avail.

Any suggestions?