It can be a bit tedious having to keep logging into remote servers to perform repeated tasks, so I have created a template script that allows me to configure a series of commands to be issued remotely.

This script is just a basic login, do, and leave, but can be added-to for basic remote tasks.

You’ll notice that the username and password is in plaintext, which is generally a no-no security-wise, but that can easily be sorted by generating a ssh keypair and adding your key to the server’s “known-hosts”. With this done you don’t need the password or username anymore.

As I said, this just a basic, connect, do and leave, and relies on Expect and the Net::OpenSSH perl module.

#!/usr/bin/perl
#######################################################################
# PERL SCRIPT TO REMOTELY LOGIN VIA OPENSSH AND RUN COMMANDS
# BY mariusv - http://www.mariusv.com
#######################################################################
use strict;
use warnings;
use Net::OpenSSH;
use Expect;
#######################################################################
$| = 1;
#######################################################################
# LOGIN DETAILS (FOR BETTER SECURITY USE SSH KEY PAIRS)
#######################################################################
my $username = 'monkey';
my $password = 'monkeymonkey';
my $enable = 'monkeys';
my $ip = '127.0.0.1';
#######################################################################
my $ssh = Net::OpenSSH->new("$username:$password\@$ip", timeout => 30);
$ssh->error and die "unable to connect to remote host: ". $ssh->error;
#ISSUE THE BASH COMMANDS YOU WANT TO PERFORM HERE ("......")
my ($pty, $pid) = $ssh->open2pty("......")
or die "unable to run remote command";
my $expect = Expect->init($pty);
$expect->raw_pty(1);
#$expect->debug(2);
my $debug and $expect->log_stdout(1);
while(<$pty>) {
print "$. $_"
}

To generate the ssh keys for passwordless logins, just do this:

[root@valhalla ~]# ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/root/.ssh/id_dsa): {Press Enter}
Created directory ‘/root/.ssh’.
Enter passphrase (empty for no passphrase): {Press Enter}
Enter same passphrase again: {Press Enter}
Your identification has been saved in /root/.ssh/id_dsa.
Your public key has been saved in /root/.ssh/id_dsa.pub.

Now login to the remote server:
[root@valhalla ~]# ssh root@SERVER
Password:
[root@SERVER ~]# vim /root/.ssh/authorized_keys
[root@valhalla ~]# vim /root/.ssh/id_dsa.pub
Now just add YOU (.ssh/id_dsa.pub) key to SERVER (.ssh/authorized_keys)

Now YOU can login to the SERVER without a password:
[root@valhalla ~]# ssh root@SERVER

That’s it. There are heaps of ways to have a Perl script login and issue commands, and there are also different types of security, this is just a basic script that gets it done quickly if you need to save some time with a few menial tasks.

Related Posts

• Extract one table from MySQL dump
• Connecting to Amazon EC2 server using ssh config file
• Perl Script to hunt and kill selected PIDs

Author: Marius Voila

Hi! My name is Marius Voila, and I am a professional system administrator, system architect, and designer.