repo2docker/docs/source/howto/export_environment.rst

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.. _export-environment:
=============================================================================
How to automatically create a ``environment.yml`` that works with repo2docker
=============================================================================
This how-to explains how to create a ``environment.yml`` that specifies all
installed packages and their precise versions from your environment.
The challenge
=============
``conda env export -f environment.yml`` creates a strict export of all packages.
This is the most robust for reproducibility, but it does bake in potential
platform-specific packages, so you can only use an exported environment on the
same platform.
``repo2docker`` uses a linux based image as the starting point for every docker
image it creates. However a lot of people use OSX or Windows as their day to
day operating system. This means that the ``environment.yml`` created by a strict
export will not work with error messages saying that certain packages can not
be resolved (``ResolvePackageNotFound``).
The solution
============
Follow this procedure to create a strict export of your environment that will
work with ``repo2docker`` and sites like `mybinder.org <https://mybinder.org/>`_.
We will launch a terminal inside a basic docker image, install the packages
you need and then perform a strict export of the environment.
#. install repo2docker on your computer by following :ref:`install`
#. in a terminal launch a basic repository
``repo2docker https://github.com/binder-examples/conda-freeze``
inside repo2docker
#. open the URL printed at the end in a browser, the URL should look like
``http://127.0.0.1:61037/?token=30e61ec80bda6dd0d14805ea76bb59e7b0cd78b5d6b436f0``
#. open a terminal by clicking "New -> Terminal" next to the "Upload" button on the
right hand side of the webpage
#. install the packages your project requires with ``conda install <yourpackages>``
#. use ``conda env export -n root`` to print the environment
#. copy and paste the environment you just printed into a ``environment.yml`` in
your projects repository
#. close your browser tabs and exit the repo2docker session by pressing Ctrl-C.
This will give you a strict export of your environment that precisely pins the
versions of packages in your environment based on a linux environment.