How to ssh from within a bash script?

Question

I am trying to create an ssh connection and do some things on the remote server from within the script.

However the terminal prompts me for a password, then opens the connection in the terminal window instead of the script. The commands don't get executed until I exit the connection.

How can ssh from within a bash script?

Answer 1

What you need to do is to exchange the SSH keys for the user the script runs as. Have a look at this tutorial

After doing so, your scripts will run without the need for entering a password. But, for security's sake, you don't want to do this for root users!

Answer 2

1. If you want the password prompt to go away then use key based authentication (described here).

2. To run commands remotely over ssh you have to give them as an argument to ssh, like the following:

   root@host:~ # ssh root@www 'ps -ef | grep apache | grep -v grep | wc -l'

Best wishes,
Fabian

Answer 3

If you want to continue to use passwords and not use key exchange then you can accomplish this with 'expect' like so:

#!/usr/bin/expect -f
spawn ssh user@hostname
expect "password:"
sleep 1
send "<your password>\r"
command1
command2
commandN

Answer 4

There's yet another way to do it using Shared Connections, ie: somebody initiates the connection, using a password, and every subsequent connection will multiplex over the same channel, negating the need for re-authentication. ( And its faster too )

# ~/.ssh/config 
ControlMaster auto
ControlPath ~/.ssh/pool/%r@%h

then you just have to log in, and as long as you are logged in, the bash script will be able to open ssh connections.

You can then stop your script from working when somebody has not already opened the channel by:

ssh ... -o KbdInteractiveAuthentication=no ....