How to get a non-interactive ssh connection

jahvascriptmaniac · 11-06-2007, 02:22 AM

Hi !

The school in which I happen to study has a network of around 500 computers. Running under Linux (yeheee !).

So I thought I could use this network like a cluster to run heavy computations (like 3D video rendering, etc.), using ssh.

I wrote a script that looks like this (the computers are named on the network a1, a2, ..., b1, b2, ...) to connect to all the computers named a* :

Code:

for ((i=0; i<25; i++)); do
    ssh a$i command
done

The problem was that it always asked my password. So I used ssh-keygen to generate a key that I added to ~/.ssh/authorized_keys, and as my home folder is shared over the network, this solved the problem, I can now connect without typing any password.

Now I still have a problem :
Each time I try to connect to a new computer, ssh looks in ~/.ssh/known_hosts and if the host isn't listed there, it asks :

Code:

The authenticity of host 'a1 (xxx.xxx.xxx.xxx)' can't be established.
RSA key fingerprint is f7:3f:6c:5c:...:16:c4:64:f4:2e:b6.
Are you sure you want to continue connecting (yes/no)?

Then, if I type "yes", the host is added to known_hosts.
I really wouldn't like to type "yes" 500 times for the first connection on each computer, so the question is :

Is there a way to tell ssh to automatically add the host to known_host and not ask if we're sure we want to connect ?
Or, how can I get from the command-line a host's key, so that I can add it manually to known_hosts ?

Thanks in advance !

{BBI}Nexus{BBI} · 11-06-2007, 07:52 PM

Check the manpage. In your terminal type: man ssh for a list of usage and options.

jahvascriptmaniac · 11-07-2007, 10:20 AM

Lol thanx for the advice, but I had already spent at least hours googeling & manpaging about ssh before posting, so either it isn't in the manpage, either I skipped it (I'll give the manpage another go, but I don't think I'll find it there).

Hope sombody knows how to do this !

bejiita · 11-09-2007, 11:05 AM

heres a link. its for gentoo

but ssh is ssh

http://gentoo-wiki.com/SECURITY_SSH_without_a_password

jahvascriptmaniac · 11-14-2007, 09:55 AM

Yeeha !
I found how to do it

It's actually really simple :
All you have to do is create a file named ~/.ssh/config, with permissions rw-r--r-- and add ONE SINGLE LINE :

Code:

StrictHostKeyChecking no

And if you don't want to change your ~/.ssh/config, you can use :

Code:

ssh -o "StrictHostKeyChecking no" host [command]

jahvascriptmaniac · 11-14-2007, 09:58 AM

P.S. : Please if sombody could set this post as "solved"... I can't find how to do it (and my mous is broken, so it's not as easy to fiddle with things with keyboard only

)

Micro420 · 11-14-2007, 10:56 AM

Thanks for posting the solution. I at least added some tags to your solution so hopefully it will help someone in the future. Certainly helped me!

jahvascriptmaniac · 11-18-2007, 03:19 AM

Oh yes, and if you don't want to change your ~/.ssh/config, you can use :

Code:

ssh -o "StrictHostKeyChecking no"

I'll add this to my previous post.