How to add SSH known host in a bash script?

Question

I am creating a bash script to provision a new server that I can deploy a web application to. One thing I always have to do is as GitHub as a known host using ssh git@github.com. How can I automate this process in a bash script, and do it in an idempotent way?

score 20 · Accepted Answer · edited May 07 '17 at 02:49

20

The simple way to go would be to do something like this.

ssh-keyscan remote_server >>~/.ssh/known_hosts

If this box is brand new you might also need to create the ~/.ssh directory before you run ssh-keyscan.

Keep in mind that ssh-keyscan can take an arbitrary number of hostnames. It will get all the keys it can.

edited May 07 '17 at 02:49

SYN

1,812

answered Dec 05 '13 at 05:29

Zoredache

133,737

score 5 · Answer 2 · answered Dec 05 '13 at 01:18

Are you trying to automate accepting the new key? If so, you could use -oStrictHostKeyChecking=no.
Doing so is a very bad idea as you're now completely wide open to man-in-the-middle attacks.

A better option would be just to manage a known_hosts file and reuse that file when you provision new servers. Stick it on github and write a simple script to download that file before sshing into github.

The strict host key checking is a good thing.

score 1 · Answer 3 · answered Dec 05 '13 at 01:17

I'm not sure i understand the question, but i think you want to ignore the known_host prompt or avoid it entirely, in which case:

ssh -o StrictHostKeyChecking=no

or other suggestions at: http://www.joedog.org/2012/07/ssh-disable-known_hosts-prompt/

How to add SSH known host in a bash script?

3 Answers3