Configuration Files

repo2docker looks for configuration files in the repository being built to determine how to build it. In general, repo2docker uses the same configuration files as other software installation tools, rather than creating new custom configuration files.

A number of repo2docker configuration files can be combined to compose more complex setups.

repo2docker will look for configuration files in either:

  • A folder named binder/ in the root of the repository.
  • The root directory of the repository.
If the folder binder/ is located at the top level of the repository,
only configuration files in the binder/ folder will be considered.

The binder examples organization on GitHub contains a list of sample repositories for common configurations that repo2docker can build with various configuration files such as Python and R installation in a repository.

Below is a list of supported configuration files (roughly in the order of build priority):


In the majority of cases, providing your own Dockerfile is not necessary as the base images provide core functionality, compact image sizes, and efficient builds. We recommend trying the other configuration files before deciding to use your own Dockerfile.

With Dockerfiles, a regular Docker build will be performed. If a Dockerfile is present, all other configuration files will be ignored.

See the Binder Documentation for best-practices with Dockerfiles.


environment.yml is the standard configuration file used by Anaconda, conda, and miniconda that lets you install Python packages. You can also install files from pip in your environment.yml as well. Our example environment.yml shows how one can specify a conda environment for repo2docker.

You can also specify which Python version to install in your built environment with environment.yml. By default, repo2docker installs Python 3.6 with your environment.yml unless you include the version of Python in the file. conda supports Python versions 3.6, 3.5, 3.4, and 2.7. repo2docker support is best with Python 3.6, 3.5, and 2.7. If you include a Python version in a runtime.txt file in addition to your environment.yml, your runtime.txt will be ignored.


This specifies a list of Python packages that should be installed in your environment. Our requirements.txt example on GitHub shows a typical requirements file.


This specifies a list of Julia packages. Repositories with a REQUIRE file must also contain an environment.yml file. To see an example of a Julia repository with REQUIRE and environment.yml, visit binder-examples/julia-python.


This is used to install R libraries pinned to a specific snapshot on MRAN. To set the date of the snapshot add a runtime.txt. For an example install.R file, visit our example install.R file.


A list of Debian packages that should be installed. The base image used is usually the latest released version of Ubuntu.

We use apt.txt, for example, to install LaTeX in our example apt.txt for LaTeX.

To install your repository like a Python package, you may include a file. repo2docker installs files by running pip install -e ..

While one can specify dependencies in, repo2docker requires configuration files such as environment.yml or requirements.txt to install dependencies during the build process.


A script that can contain arbitrary commands to be run after the whole repository has been built. If you want this to be a shell script, make sure the first line is `#!/bin/bash.

An example use-case of postBuild file is JupyterLab’s demo on It uses a postBuild file in a folder called binder to prepare their demo for binder.


A script that can contain simple commands to be run at runtime (as an ENTRYPOINT <> to the docker container). If you want this to be a shell script, make sure the first line is `#!/bin/bash. The last line must be `exec "$@"` equivalent.

Use this to set environment variables that software installed in your container expects to be set. This script is executed each time your binder is started and should at most take a few seconds to run.

If you only need to run things once during the build phase use postBuild.


This allows you to control the runtime of Python or R.

To use python-2.7: add python-2.7 in runtime.txt file. The repository will run in a virtualenv with Python 2 installed. To see a full example repository, visit our Python2 example. Python versions in ``runtime.txt`` are ignored when environment.yml is present in the same folder.

repo2docker uses R libraries pinned to a specific snapshot on MRAN. You need to have a runtime.txt file that is formatted as r-<YYYY>-<MM>-<DD>, where YYYY-MM-DD is a snapshot at MRAN that will be used for installing libraries.

To see an example R repository, visit our R example in binder-examples.