Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

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?

share|improve this question
up vote 3 down vote accepted

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.

share|improve this answer
Yes, I came to the same conclusion: leave the passphrase blank and limit the usage of the key so that it can only execute the backup-script. – Jannemans Jun 20 '11 at 7:29
It is possible to use keychain to access ssh-agent from cron. For details see following article -…. – AlexD Jun 20 '11 at 16:20

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.