16.10.2009

Batch processing: ssh access to multiple servers without ssh-keys

It is always the same: You are used to a technique like
  • accessing server via ssh with ssh-keys
But in some environments you are not allowed or you just don't want to put your authorized_keys to the servers, which you want to access. But how to automate logins to this servers?
  1. Poor man's approach
    buffer the password and use the middle button on your mouse, each time the script asks for the password.
    This works, but this is only "semi-automatic"
  2. Use expect
    With this tool it is very easy to automate logins without using ssh-keys. Just write a script auto.ssh.sh like this:
#!/usr/bin/expect
spawn ssh -l root $argv
expect "Password: "
send "mypassword\n"
expect "#";
send "date\n";
expect "#";
send "exit\n";
This script can be called with a parameter (here IP or hostname) and executes the date command on the server. Now just write a loop:
for server in 10.0.0.1 10.0.0.2 10.0.0.3; do ./auto.ssh.sh $server; done
And you are done...
(But this is not so secure like using ssh-keys!)

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