[vox-tech] crontab and scp puzzle

[Bruce Wolk]

I need to copy a file from my server to a workstation on a regular 
basis.  I have set up passwordless ssh access to the server from my 
workstation.  When I execute the following on the workstation, the 
command succeeds and the file is copied:

scp -P 33303 bruce at myserver.com:backup/db.sql.gz 
/home/bruce/backup/db.sql.gz

But when I put the same command into a cron file on the workstation, the 
command fails.  The relevant output from the scp command is:

debug1: Found key in /home/bruce/.ssh/known_hosts:5
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: /home/bruce/.ssh/id_rsa.pub
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug1: PEM_read_PrivateKey failed
debug1: read PEM private key done: type <unknown>
debug1: read_passphrase: can't open /dev/tty: No such device or address
debug1: No more authentication methods to try.
Permission denied (publickey).

I edited the cron file using crontab -e and have verified that it is 
excecuting properly as user bruce.

I googled around but found nothing that helps.  Why would the 
authentication work with direct execution, but fail with cron execution? 
  Does anyone have any ideas?

Bruce