[vox-tech] crontab and scp puzzle

[Kyle Ambroff]

I know I've used this answer before on this list, and I'm sure it's
annoying, but if your solution involves passphraseless ssh keys, you're
doing it wrong.

That being said, since cron is a daemon, it is not attached to a controlling
terminal. That means that a script that expects to be able to read input
from the user is going to fail. You can probably force it to bypass this
code with BatchMode.

    ssh -o BatchMode=yes ...

For good measure, you could even set TERM if it's not being set.

    env TERM=dumb ssh -o BatchMode=yes ...

On Wed, Mar 16, 2011 at 9:43 AM, Bruce Wolk <bawolk at ucdavis.edu> wrote:

> 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
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