rsync + ssh: fails from cron

[Itay Furman]

Hi,

My ssh set up, on both 'work' and 'home' machines uses the 
private-public key authentication (key uses non-empty 
passphrase). So from the 'home' shell prompt the following 
works without prompting to password or passphrase:

rsync -avz --delete -e ssh remote.work.machine:publicats $HOME/work

>From cron, however, I am prompted for a password, though.

I have seen several posts in this regard on the list. Some 
mentioned using keys with no passphrases -- the others I was not 
able to understand at all due to my incompetence.

Is there a way to use a key with no passphrase (only for the 
purpose of rsyncing my two file systems via cron) _along_ with my 
current set up (for the rest of ssh uses)?
or do I have to give up the passphrase altogether? (isn't it a 
security issue, then?)

I am aware that it is not strictly an rsync question, but this 
issue of using ssh surfaces up when ssh is _coupled_ to rsync and 
cron.

I would appreciate any suggestions, comments, examples.

	Thanks a lot!
	Itay Furman

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itayf at fhcrc.org		Fred Hutchinson Cancer Research Center