# Ensure reproducibility for your Binder¶

Binder will create a new Docker image the first time is run with a repository. From then on, a new image will only be created if the commit hash changes (if you’re linking Binder to a branch and not a specific commit hash). Here are some tips to ensure reproducibility of your Binder links even if you must re-build your repository image:

## Pin dependencies¶

When you install a dependency, include its version number (depending on the language you use, the exact syntax may vary). E.g., don’t just specify numpy, specify numpy==1.12.0.

pip freeze is a handy tool to export the exact version of every Python package in your environment in a format that can be used in requirements.txt.

conda env export -n <env-name> is the equivalent for anaconda’s environment.yml file.

When exporting a conda environment, you can add the conda-forge broken channel (conda-forge/label/broken) as a low-priority channel in your exported environment.yml file in order to maximize durability. Thus, if a package is marked broken after you froze the environment, said package will still install during the Binder image build process. Only do this when you intend to truly freeze the environment.

For example (in environment.yml):

channels:
- conda-forge
- defaults
- conda-forge/label/broken


## Using Dockerfiles¶

Ensuring reproducibility with Dockerfiles comes with its own set of challenges. For more information and best-practices when using Dockerfiles for Binder, see Use a Dockerfile for your Binder.