using ssh keys in bash script

Question

I've setup ssh keys form server A to server B and I can login to server B without a password. I'm trying to setup a reverse ssh tunnel in a bash script. From the command line if I do

ssh -N -R 1234:localhost:22 [email protected] -p 22

form server A it works as expected i.e no password required, however if I use it in a script

#!/bin/bash
/usr/bin/ssh -N -R 1234:localhost:22 [email protected] -p 22

I get asked for the password

[email protected]'s password:

How do I make it so it uses the keys?

Answer 1

You need to let ssh know where it should search for the keys, if they are not in standard location and not passphrase protected. The easiest thing is by specifying -i switch directly to ssh:

/usr/bin/ssh -i /path/to/key -N -R 1234:localhost:22 [email protected] -p 22

Or cleaner way in your ~/.ssh/config like this:

Host mydomain.co.uk
  IdentityFile /path/to/key

But make sure the script is run with your user context, so the script will see the configuration file.

If you have keys in standard location (~/.ssh/id_rsa), your code should work just fine. Although it should work if you have your keys stored in ssh-agent, which you can verify using ssh-add -L before starting the script. ssh-agent also solve the problem, if he keys are passphrase protected.