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https://github.com/xolox/python-redock

Human friendly wrapper around Docker
https://github.com/xolox/python-redock

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Human friendly wrapper around Docker

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redock: A human friendly wrapper around Docker

==============================================



Redock is a human friendly wrapper around Docker_, the `Linux container

engine`_. Docker implements a lightweight form of virtualization_ that makes it

possible to start and stop "virtual machines" in less than a second. Before

Docker the use of virtualization meant conventional virtual machines with all

of the associated bloat. Docker makes it ridiculously cheap and fast to

start/save/kill containers. This opens up exciting new possibilities for

DevOps:



- Complex build environments can be split up into isolated containers where

  each container is concerned with the build requirements of a single project.

  If a project's build goes out of hand you just trash the container and go on

  your merry way :-)



- The correctness of automated deployment systems (and distributed systems in

  general) can be verified by using containers to host the configuration

  management server and agents.



- To be honest, Docker is so fast that I could imagine myself building a test

  suite of a complete cluster on top of it.



The last point is the reason why I started working on Redock. In my initial

experiments with Docker_ I found a lot of sharp edges (both in the lack of

documentation and in the implementation of Docker_ and its Python API) but at

the same time my fingers were itching to wrap Docker in an easy to use and

human friendly wrapper to try and unleash its potential.



What Redock gives you is Docker without all the hassle: When you create a

container, Redock will install, configure and start an SSH_ server and open

an interactive SSH session to the container. What you do with the container

after that is up to you...



Status

------



Redock should be considered alpha quality software. So far it has been used by

a single person (me). Right now it's intended for development work, not

production use. This might change over time, depending on my experiences with

Docker over the coming weeks / months (I'm specifically concerned with

stability and performance).



By the way the same can and should be said about Docker_ (its site says as

much). During heavy testing of Redock I've experienced a number of unhandled

kernel mode NULL pointer dereferences that didn't crash the host system but

certainly also didn't inspire confidence ;-). It should be noted that these

issues didn't occur during regular usage; only heavy testing involving the

creation and destruction of dozens of Docker containers would trigger the

issue.



There's one thing I should probably mention here as a disclaimer: Redock

rewrites your SSH configuration (``~/.ssh/config``) using update-dotdee_. I've

tested this a fair bit, but it's always a good idea to keep backups (hint).



I'm currently using Redock on Ubuntu 12.04 with Docker 0.6.3 and a Linux 3.8.0

kernel (as suggested in Docker's `installation instructions`_ for Ubuntu). I've

only just switched to these versions and it seems they may have solved the

stability issues I mentioned above (time will tell :-).



Usage

-----



You will need to have Docker_ installed before you can use Redock, please refer

to Docker's `installation instructions`_. You may also want to add your user

account to the ``docker`` group so you can connect to Docker without ``sudo``

(this took me a while to realize when I switched to Docker 0.6 :-). After

you've installed Docker you can install Redock using the following command::



    $ pip install redock



This downloads and installs Redock using pip_ (the Python package manager).

Redock is written in Python so you need to have Python installed. Redock pulls

in a bunch of dependencies_ so if you're familiar with `virtual environments`_

you might want to use one :-). Once you've installed Docker and Redock, here's

how you create a container::



    $ redock start test



If you run this command interactively and you start a single container, Redock

will start an interactive SSH_ session that connects you to the container. In

any case you will now be able to connect to the container over SSH_ using the

name you gave to the container suffixed with ``-container``::



    $ ssh test-container



This works because your ``~/.ssh/config`` has been updated to include a host

definition for the container. This means you can connect using rsync_ or

anything else which works on top of SSH_ (e.g. to bootstrap a configuration

management system). When you're done playing around with the container you can

save your changes with the following command::



    $ redock commit test



This command will persist the state of the container's file system in a Docker

image. The next time you run Redock with the same name it will create a

container based on the existing disk image. To kill and delete a running

container you use the following command::



    $ redock kill test



This will discard all changes made to the file system inside the container

since the last time that ``redock commit`` was used. The Docker image

associated with a container can be deleted like this::



    $ redock delete test



Naming conventions

~~~~~~~~~~~~~~~~~~



In the examples above the name ``test`` is used. This name is used by Redock to

identify the running container (created with ``redock start``) and any

associated images (created with ``redock commit``). By using multiple names you

can run multiple containers in parallel and you can suspend / resume "long

term" containers.



The names accepted by Redock are expected to be of the form ``repository:tag``

(two words separated by a colon):



1. The first part (``repository`` in the example) is a top level name space for

   Docker images. For example there is a repository called ``ubuntu`` that

   contains the official base images. Similarly Redock uses the repository

   ``redock`` for the base image it creates on the first run.



2. The second part (``tag`` in the example) is the name of a specific container

   and/or image; I usually just sets it to the host name of the system that

   will be running inside the container.



If the colon is missing the ``repository`` will be set to your username (based

on the environment variable ``$USER``).



Contact

-------



The latest version of Redock is available on PyPI_ and GitHub_. The API

documentation is `hosted on Read The Docs`_. For bug reports please create an

issue on GitHub_. If you have questions, suggestions, etc. feel free to send me

an e-mail at `[email protected]`_.



License

-------



This software is licensed under the `MIT license`_.



© 2013 Peter Odding.



.. External references:

.. _dependencies: https://github.com/xolox/python-redock/blob/master/requirements.txt

.. _Docker: http://www.docker.io/

.. _GitHub: https://github.com/xolox/python-redock

.. _hosted on Read The Docs: https://redock.readthedocs.org/en/latest/

.. _installation instructions: http://www.docker.io/gettingstarted/

.. _Linux container engine: http://en.wikipedia.org/wiki/LXC

.. _MIT license: http://en.wikipedia.org/wiki/MIT_License

.. [email protected]: [email protected]

.. _pip: http://www.pip-installer.org/

.. _PyPI: https://pypi.python.org/pypi/redock

.. _rsync: http://en.wikipedia.org/wiki/Rsync

.. _SSH: http://en.wikipedia.org/wiki/Secure_Shell

.. _update-dotdee: https://pypi.python.org/pypi/update-dotdee

.. _virtual environments: http://www.virtualenv.org/

.. _virtualization: http://en.wikipedia.org/wiki/Virtualization