SSH-agent & SSH-add at reboot

Question

Situation: Running Ubuntu 10.04. I have a bash script that tar's a bunch of folders and copies them to another host over ssh. I've copied the public key to the other host so it doesn't prompt for a password. I run eval ssh-agent (with extra quotes) and ssh-add to cache to passphrase and after that I can run the script without it prompting for anytime. So far so good.

Problem: I want to run this script through a cronjob, under my own user for now (this is just a test-setup). But when I restart the machine, ssh-agent loses the keys I added via ssh-add and I have to do eval ssh-agent & ssh-add again to get it working.

Question: - How do I make ssh-agent run at all times? (since there won't be a user logged in when the cronjob runs) - How do I permanently save my rsa_id to ssh-add?

Answer 1

You would need to leave the pass-phrase on the ssh key blank when you create it. That way you won't need to use ssh-agent. Clearly there are security implications of that choice - but ssh-agent will always require you to enter the pass-phrase first time if the key is protected.

Technically, you could probably use expect to pass a pass-phrase to ssh-agent from a script - but if you're prepared to put your pass-phrase into a script you may as well just leave it blank.

The usual way to improve security if you follow this route is to only allow the key in question access to a specifically crafted / restricted account on the other server.