Getting started with Parameko

First a short disclaimer. I a system administrator write this article with very little python programming experience taking the risk of sounding like an amateur to a seasoned python programming pro. But I felt this is something interesting & felt the need to share.

Parameko is a python module that can be used to automate the work we do with ssh to some extent.

It's available in the EPEL repository & can be installed by running the command 'yum install python-parameko'.

In my centOS 7 system the rpm installed was python2-paramiko-1.16.1-1.el7.noarch.rpm.

[root@devbox epel]# rpm -qi python2-paramiko

Name        : python2-paramiko

Version     : 1.16.1

Release     : 1.el7

Architecture: noarch

Install Date: Fri 02 Sep 2016 05:47:37 AM PDT

Group       : Development/Libraries

Size        : 1262230

License     : LGPLv2+

Signature   : RSA/SHA256, Mon 16 May 2016 08:38:58 PM PDT, Key ID 6a2faea2352c64e5

Source RPM  : python-paramiko-1.16.1-1.el7.src.rpm

Build Date  : Mon 16 May 2016 09:02:33 AM PDT

Build Host  : buildvm-07.phx2.fedoraproject.org

Relocations : (not relocatable)

Packager    : Fedora Project

Vendor      : Fedora Project

URL         : https://github.com/paramiko/paramiko/

Summary     : SSH2 protocol library for python

Description :

Paramiko (a combination of the esperanto words for "paranoid" and "friend") is

a module for python 2.3 or greater that implements the SSH2 protocol for secure

(encrypted and authenticated) connections to remote machines. Unlike SSL (aka

TLS), the SSH2 protocol does not require heirarchical certificates signed by a

powerful central authority. You may know SSH2 as the protocol that replaced

telnet and rsh for secure access to remote shells, but the protocol also

includes the ability to open arbitrary channels to remote services across an

encrypted tunnel. (This is how sftp works, for example.)

Python 2 version.

Obviously we'll start things with the 'Hello World' example. So here it is:

#!/usr/bin/python

import paramiko

import sys

import os

ssh = paramiko.SSHClient()

ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

ssh.connect('127.0.0.1', username='james', password='123')

stdin, stdout, stderr = ssh.exec_command('echo "hello world"' )

a = stdout.read().strip()

print a

Code breakdown:

The primary class of the Paramiko API is ''paramiko.SSHClient''. It provides the basic interface for instantiating ssh connections. This creates a new SSHClient object, and then calls ''connect()'' to connect us to the local SSH server.

Whenever we make an ssh connection to a remote machine, that host's key is stored automatically in a file in your home directory called ''.ssh/known_hosts''.

Passing paramiko.AutoAddPolicy() to the set_missing_host_key_policy client object will auto accept unknown host keys.

Within ssh.connect() object we specify the host/IP address we need to connect to & the credentials to use.

ssh.exec_command() object contains the command we need to execute.

In the next example, we run multiple commands on host 192.168.44.135:

[root@devbox ~]# cat test.py

#!/usr/bin/python

import paramiko

import sys

import os

ssh = paramiko.SSHClient()

ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

ssh.connect('192.168.44.135', username='james', password='123')

stdin, stdout, stderr = ssh.exec_command('uname -a ; uptime')

a = stdout.read().strip()

print a

This outputs to:

[root@devbox ~]# ./test.py

Linux rheldb 2.6.32-220.el6.x86_64 #1 SMP Wed Nov 9 08:03:13 EST 2011 x86_64 x86_64 x86_64 GNU/Linux

 06:12:04 up 2 min,  1 user,  load average: 0.90, 0.74, 0.30

In the final example, we run commands across multiple hosts:

[root@devbox ~]# cat mul.py

#!/usr/bin/python

import sys, os, string, threading

import paramiko

cmd = "uname -a; who -r"

outlock = threading.Lock()

def workon(host):

    ssh = paramiko.SSHClient()

    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

    ssh.connect(host, username='james', password='123')

    stdin, stdout, stderr = ssh.exec_command(cmd)

    stdin.flush()

    with outlock:

        print stdout.readlines()

def main():

    hosts = ['192.168.44.137', '192.168.44.135' ]

    threads = []

    for h in hosts:

        t = threading.Thread(target=workon, args=(h,))

        t.start()

        threads.append(t)

    for t in threads:

        t.join()

main()

The above code outputs to:

[root@devbox ~]# ./mul.py

[u'Linux devbox 3.10.0-123.el7.x86_64 #1 SMP Mon Jun 30 12:09:22 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux\n', u'         run-level 5  2016-09-02 12:24\n']

[u'Linux rheldb 2.6.32-220.el6.x86_64 #1 SMP Wed Nov 9 08:03:13 EST 2011 x86_64 x86_64 x86_64 GNU/Linux\n', u'         run-level 3  2016-09-03 11:40\n']

The examples in this article are intended to be a very basic quick start to using parameko to help automate some of the repetitive tasks involving logging in to remote systems. 

I will definitely update this article as my python & parameko understanding matures over time.