Tag Archives: windows

Using Paramiko to control an EC2 instance

An example of using Paramiko to issue commands to an EC2 instance


An example of using the Python library Paramiko to ‘remote control’ an EC2 instance .

“Do that, Do this”

Recently I’ve been looking into the use of the Bellatrix library to start, control and stop Amazon EC2 instances (my posts about that are here and here).

Spinning off the side of that I’ve taken a look at the Paramiko module which “implements the SSH2 protocol for secure (encrypted and authenticated) connections to remote machines”.

There’s a good article on beginning to use Paramiko “SSH Programming with Paramiko” by Jesse Noller which I found very helpful but there’s enough stuff I had to change to deal with using EC2 and the controlling Python script running on Windows that I thought it would be worth recording my sample script.

Installing Paramiko

So first off I’d seen the comments about Paramiko maybe needing a special compilation step for installation to Windows but I’m pleased to say that’s not true, I downloaded to my Windows Vista machine, did a quick…

python setup.py install

… and it all went very smoothly, just to be sure I tried out an import …

>>> import paramiko

… no problem.

Starting the EC2 instance

I now needed a server to talk to so I used Bellatrix to spin up a micro instance of Ubuntu like this :

python "C:\bin\installed\Python2.6\Scripts\bellatrix" start --security_groups mySecGrp ami-3e9b4957 mykeypair

The arguments you can see here are :

  • “mySecGrp” is a Security Group I’ve previously setup via the AWS Management Console;
  • ‘ami-3e9b4957′ is the AMI of Ubuntu 10.04 (Lucid Lynx); and
  •  ‘mykeypair’ is the name of a Key Pair that, again, I’ve previously setup via the AWS Management Console.

When you run that command you get an output that looks like this :

C:\Users\Richard Shea>python "C:\bin\installed\Python2.6\Scripts\bellatrix" start --security_groups mySecGrp ami-3e9b4957 mykeypair
2012-04-19 21:27:03,135 INFO starting EC2 instance...
2012-04-19 21:27:03,180 INFO ami:ami-3e9b4957 type:t1.micro key_name:mykeypair security_groups:mySecGrp new size:None
2012-04-19 21:27:07,657 INFO starting image: ami-3e9b4957 key mykeypair type t1.micro shutdown_behavior terminate new size None
2012-04-19 21:27:08,555 INFO we got 1 instance (should be only one).
2012-04-19 21:27:08,556 INFO tagging instance:i-f1234567 key:Name value:Bellatrix started me
2012-04-19 21:27:12,361 INFO instance:i-f1234567 was successfully tagged with: key:Name value:Bellatrix started me
2012-04-19 21:27:12,361 INFO getting the dns name for instance: i-f1234567 time out is: 300 seconds...
2012-04-19 21:27:34,173 INFO DNS name for i-f1234567 is ec2-10-20-30-40.compute-1.amazonaws.com
2012-04-19 21:27:34,173 INFO waiting until instance: i-f1234567 is ready. Time out is: 300 seconds...
2012-04-19 21:27:34,174 INFO Instance i-f1234567 is running

And the key thing here is that we now now have access to the host name of the EC2 instance we’ve just spun up:


Talking to the EC2 instance

We’re now ready to send commands to our new instance. Making use of some of Jesses code I was able to write :

import paramiko
ssh = paramiko.SSHClient()
stdin, stdout, stderr = ssh.exec_command("uptime;ls -l;touch mickymouse;ls -l;uptime")
data = stdout.read().splitlines()
for line in data:
    print line

Anyone who’s got this far can probably see what’s happening here, but just to be sure :

  1. having instantiated an instance of paramiko.SSHClient we’re able to use our private key file and the address of our EC2 server to start an SSH session.
  2. We then use the exec_command method to submit a string of commands and get back three references to files corresponding to : standard input, standard output and standard error.
  3. By reading through the standard output file we can print locally the output from the commands executed on the EC2 instance.

The Key Thing

As you can see to identify ourselves to the remote server we’re doing a key exchange. Our private key is ‘mykeypair-ssh2-rsa.openssh’. A point worth mentioning here is that generally I logon to EC2 instances using the excellent PuTTY . The private key files used by default by PuTTY are not in the same format as the ones required by Paramiko so as a result when I first tried this I found Paramiko fell over complaining my ‘key_filename’ argument was ‘not a valid dsa private key file’.

PuttyGen to the rescue

Well the great thing is that PuTTY actually comes with a tool PuttyGen which will import a standard PuTTY key file (foo.ppk) – you need to do ‘Conversions’ | ‘Import Key’ and then ‘Conversions’ | ‘Export OpenSSH Key’

Ubuntu Specific

Bear in mind that the way the SSHClient connect method is used above is suitable for an Ubuntu instance as it is by default however you can’t rely on all *nix instance working just that way.

Seeing the Output

Just to close out I’ll show you the output

12:39:45 up  3:12,  0 users,  load average: 0.08, 0.02, 0.01
total 0
total 0
-rw-r--r-- 1 ubuntu ubuntu 0 2012-04-19 12:39 mickymouse
12:39:45 up  3:12,  0 users,  load average: 0.08, 0.02, 0.01

Powerful Stuff

The combination of Bellatrix allowing you to spin up EC2 instances with a single command and Paramiko allowing you send arbitary commands to those servers is powerful stuff and I’m impressed at the work done by their respective developers. Of course Bellatrix can do ‘for free’ what I’ve used Paramiko to do here are part of it’s Provisioning commands but it was an interesting exercise for me to do my own version of that.

Taking your PIL with py2exe

Letting PIL and py2exe be friends

Escape from “cannot identify image file” hell


The Python Imaging Library (PIL) provides great image manipulation help for your python programs. Py2exe provides a smart way of turning a python script into a windows executable. There are times however when the resulting .exe will break if you don’t do the right thing.

My Problem

I’d written a Python script, openpilwithdiag.py, which read TIFF files and worked just fine when run through the Python interpreter.

from PIL import Image
im = Image.open("test.TIFF")
print im.getcolors()

I then used py2exe to convert the script to a .exe.  Aargh – when I went to run it I got an error :

IOError: cannot identify image file

It took a little digging around but it seems that when PIL constructs one of its PIL Image objects it searches a set of ‘image plugin’ files within the PIL installation. This is all good except that by the time py2exe has done it’s thing PIL (now nicely wrapped up inside the .exe) will be looking in the wrong place.

The Solution

Pleasantly simple – given all the blind alleys I looked down to start with ! I’d previously had nasty problems using TIFF files with PIL and I think I started looking at this expecting the answer to be really nasty !

Whatever file formats you want to use import the corresponding PIL plugin directly into the script so that the instantiation of Image can ‘see’ them. For my example that’s like this :

from PIL import Image
from PIL import TiffImagePlugin
im = Image.open("test.TIFF")
print im.getcolors()

Tried py2exe again and what do we get ?

[(37306, (76, 25, 12, 51)), (42810, (0, 0, 0, 255)), (1489484, (0, 0, 0, 0))]

Much better !

Plugin Details

The set of possible plugins may be found by looking for files named xImagePlugin.py (where x is the name of the supported format) within the sub-directory of your Python installation at :

<your python directory>\Lib\site-packages\PIL

A list of file formats PIL supports is seen in the appendix of the PIL Handbook


It occurs to me that for anyone who’s never touched py2exe it might be worth posting the setup.py I was using to drive the py2exe process – so here it is :

from distutils.core import setup
import glob
import py2exe