How do I make ssh fail rather than prompt for a password if the public-key authentication fails?

Question

I've got a script that ssh'es several servers using public key authentication. One of the servers has stopped letting the script log in due to a configuration issue, which means that the script gets stuck with a "Password:" prompt, which it obviously cannot answer, so it doesn't even try the rest of the servers in the list.

Is there a way to tell the ssh client not to prompt for a password if key authentication fails, but instead to just report an error connecting and let my script carry on?

Answer 1

For OpenSSH there's also BatchMode which in addition to disabling password prompting should disable querying for passphrase(s) for keys.

BatchMode

If set to “yes”, passphrase/password querying will be disabled. This option is useful in scripts and other batch jobs where no user is present to supply the password. The argument must be “yes” or “no”. The default is “no”.

Sample usage:

ssh -oBatchMode=yes -l <user> <host> <dostuff>

Answer 2

add the following to your ~/.ssh/config:

PasswordAuthentication no

and to disable password auth on the server, add the same line to /etc/ssh/sshd_config and restart sshd.

Answer 3

On the command line (or ~/.ssh/config) you can set PreferredAuthentications.

PreferredAuthentications public-key

Answer 4

If you are using dropbear, just add the "-s" option to disable password authentication.