Non interactive SSH

When running VRPipe in a cluster of many nodes, in certain circumstances (especially when using the ec2-related schedulers) the vrpipe-server must be able to ssh to and run commands on any node in the cluster. This will fail if the user running vrpipe-server normally has to answer some question when doing an ssh login to a node for the first time (eg. entering a password, or accepting the authenticity).

To ensure ssh will succeed, you can make logins non-interactive by following this guide for the user that will run vrpipe-server.

1. Alter the ssh config to turn off host key checking and make ssh quiet.
   nano ~/.ssh/config and enter the following:
   Host *
   UserKnownHostsFile=/dev/null
   StrictHostKeyChecking=no
   LogLevel=quiet
   (then ctrl-x, y, return to save)
chmod 644 ~/.ssh/config
2. If there are no security concerns (eg. you're not in the middle of creating a public AMI on the Amazon cloud; private ones are OK), also create a passphrase-less self-authorizing key:
   ssh-keygen -t dsa
   Hit return 3 times to accept the defaults, then:
   cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys