repo2docker/docs/source/faq.md

# Frequently Asked Questions (FAQ)

A collection of frequently asked questions with answers. If you have a question
and have found an answer, send a PR to add it here!

## How should I specify another version of Python 3?

One can specify a Python version in the ``environment.yml`` file of a repo.

## Can I add executable files to the user's PATH?

Yes! With a :ref:`postBuild` file, you can place any files that should be called
from the command line in the folder ``~/.local/``. This folder will be
available in a user's PATH, and can be run from the command line (or as
a subsequent build step.)

## How do I set environment variables?

Use the `-e` or `--env` flag for each variable that you want to define.

For example `jupyter-repo2docker -e VAR1=val1 -e VAR2=val2 ...`

## Can I use repo2docker to bootstrap my own Dockerfile?

No, you can't.

If you pass the `--debug` flag to `repo2docker`, it outputs the intermediate
Dockerfile that is used to build the docker image. While it is tempting to copy
this as a base for your own Dockerfile, that is not supported & in most cases
will not work. The `--debug` output is just our intermediate generated
Dockerfile, and is meant to be built in
[a very specific way](https://github.com/jupyter/repo2docker/blob/master/repo2docker/detectors.py#L381).
Hence the output of `--debug` can not be built with a normal `docker build -t .`
or similar traditional docker command.

Check out the [binder-examples](http://github.com/binder-examples/) github
organization for example repositories you can copy & modify for your own use!