Try adding "-e ssh" to your rsync command.
Search for "-e" in the rsync man page for an example.


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This is the crontab entry (in rmason's crontab):

0,15,30,45 * * * *      rmason /usr/bin/rsync -av /home/rmason backup_machine:mymachine_rmason
I have passwordless ssh between mymachine and backup_machine and the
rsync command in the crontab runs perfectly from the command line.

Does someone know what else needs to be done to get this (seemingly
simple!) task to work?