jupyterhub/docs/source/contributing/setup.md

(contributing/setup)=

# Setting up a development install

## System requirements

JupyterHub can only run on macOS or Linux operating systems. If you are
using Windows, we recommend using [VirtualBox](https://virtualbox.org)
or a similar system to run [Ubuntu Linux](https://ubuntu.com) for
development.

### Install Python

JupyterHub is written in the [Python](https://python.org) programming language and
requires you have at least version 3.6 installed locally. If you haven’t
installed Python before, the recommended way to install it is to use
[Miniforge](https://github.com/conda-forge/miniforge#download).

### Install nodejs

[NodeJS 12+](https://nodejs.org/en/) is required for building some JavaScript components.
`configurable-http-proxy`, the default proxy implementation for JupyterHub, is written in Javascript.
If you have not installed NodeJS before, we recommend installing it in the `miniconda` environment you set up for Python.
You can do so with `conda install nodejs`.

Many in the Jupyter community use \[`nvm`\](<https://github.com/nvm-sh/nvm>) to
managing node dependencies.

### Install git

JupyterHub uses [Git](https://git-scm.com) & [GitHub](https://github.com)
for development & collaboration. You need to [install git](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git) to work on
JupyterHub. We also recommend getting a free account on GitHub.com.

## Setting up a development install

When developing JupyterHub, you would need to make changes and be able to instantly view the results of the changes. To achieve that, a developer install is required.

:::{note}
This guide does not attempt to dictate _how_ development
environments should be isolated since that is a personal preference and can
be achieved in many ways, for example, `tox`, `conda`, `docker`, etc. See this
[forum thread](https://discourse.jupyter.org/t/thoughts-on-using-tox/3497) for
a more detailed discussion.
:::

1. Clone the [JupyterHub git repository](https://github.com/jupyterhub/jupyterhub)
   to your computer.

   ```bash
   git clone https://github.com/jupyterhub/jupyterhub
   cd jupyterhub
   ```

2. Make sure the `python` you installed and the `npm` you installed
   are available to you on the command line.

   ```bash
   python -V
   ```

   This should return a version number greater than or equal to 3.6.

   ```bash
   npm -v
   ```

   This should return a version number greater than or equal to 5.0.

3. Install `configurable-http-proxy` (required to run and test the default JupyterHub configuration) and `yarn` (required to build some components):

   ```bash
   npm install -g configurable-http-proxy yarn
   ```

   If you get an error that says `Error: EACCES: permission denied`, you might need to prefix the command with `sudo`.
   `sudo` may be required to perform a system-wide install.
   If you do not have access to sudo, you may instead run the following commands:

   ```bash
   npm install configurable-http-proxy yarn
   export PATH=$PATH:$(pwd)/node_modules/.bin
   ```

   The second line needs to be run every time you open a new terminal.

   If you are using conda you can instead run:

   ```bash
   conda install configurable-http-proxy yarn
   ```

4. Install an editable version of JupyterHub and its requirements for
   development and testing. This lets you edit JupyterHub code in a text editor
   & restart the JupyterHub process to see your code changes immediately.

   ```bash
   python3 -m pip install --editable ".[test]"
   ```

5. Set up a database.

   The default database engine is `sqlite` so if you are just trying
   to get up and running quickly for local development that should be
   available via [Python](https://docs.python.org/3.5/library/sqlite3.html).
   See [The Hub's Database](hub-database) for details on other supported databases.

6. You are now ready to start JupyterHub!

   ```bash
   jupyterhub
   ```

7. You can access JupyterHub from your browser at
   `http://localhost:8000` now.

Happy developing!

## Using DummyAuthenticator & SimpleLocalProcessSpawner

To simplify testing of JupyterHub, it is helpful to use
{class}`~jupyterhub.auth.DummyAuthenticator` instead of the default JupyterHub
authenticator and SimpleLocalProcessSpawner instead of the default spawner.

There is a sample configuration file that does this in
`testing/jupyterhub_config.py`. To launch JupyterHub with this
configuration:

```bash
jupyterhub -f testing/jupyterhub_config.py
```

The default JupyterHub [authenticator](PAMAuthenticator)
& [spawner](LocalProcessSpawner)
require your system to have user accounts for each user you want to log in to
JupyterHub as.

DummyAuthenticator allows you to log in with any username & password,
while SimpleLocalProcessSpawner allows you to start servers without having to
create a Unix user for each JupyterHub user. Together, these make it
much easier to test JupyterHub.

Tip: If you are working on parts of JupyterHub that are common to all
authenticators & spawners, we recommend using both DummyAuthenticator &
SimpleLocalProcessSpawner. If you are working on just authenticator-related
parts, use only SimpleLocalProcessSpawner. Similarly, if you are working on
just spawner-related parts, use only DummyAuthenticator.

## Troubleshooting

This section lists common ways setting up your development environment may
fail, and how to fix them. Please add to the list if you encounter yet
another way it can fail!

### `lessc` not found

If the `python3 -m pip install --editable .` command fails and complains about
`lessc` being unavailable, you may need to explicitly install some
additional JavaScript dependencies:

```bash
npm install
```

This will fetch client-side JavaScript dependencies necessary to compile
CSS.

You may also need to manually update JavaScript and CSS after some
development updates, with:

```bash
python3 setup.py js    # fetch updated client-side js
python3 setup.py css   # recompile CSS from LESS sources
python3 setup.py jsx   # build React admin app
```