jupyterhub/docs/getting-started.md

# Getting started with JupyterHub

This document describes some of the basics of configuring JupyterHub to do what you want.
JupyterHub is highly customizable, so there's a lot to cover.


## Installation

See [the readme](../README.md) for help installing JupyterHub.


## Overview

JupyterHub is a set of processes that together provide a multiuser Jupyter Notebook server.
There are three main categories of processes run by the `jupyterhub` command line program:

- *Single User Server*: a dedicated, single-user, Jupyter Notebook is started for each user on the system
  when they log in. The object that starts these processes is called a *Spawner*.
- *Proxy*: the public facing part of the server that uses a dynamic proxy to route HTTP requests
  to the *Hub* and *Single User Servers*.
- *Hub*: manages user accounts and authentication and coordinates *Single Users Servers* using a *Spawner*.

## JupyterHub's default behavior


To start JupyterHub in its default configuration, type the following at the command line:

    sudo jupyterhub

The default Authenticator that ships with JupyterHub authenticates users
with their system name and password (via [PAM][]).
Any user on the system with a password will be allowed to start a single-user notebook server.

The default Spawner starts servers locally as each user, one dedicated server per user.
These servers listen on localhost, and start in the given user's home directory.

By default, the *Proxy* listens on all public interfaces on port 8000.
Thus you can reach JupyterHub through:

    http://localhost:8000

or any other public IP or domain pointing to your system.

In their default configuration, the other services, the *Hub* and *Single-User Servers*,
all communicate with each other on localhost only.

**NOTE:** In its default configuration, JupyterHub runs without SSL encryption (HTTPS).
You should not run JupyterHub without SSL encryption on a public network.
See [below](#Security) for how to configure JupyterHub to use SSL.

By default, starting JupyterHub will write two files to disk in the current working directory:

- `jupyterhub.sqlite` is the sqlite database containing all of the state of the *Hub*.
  This file allows the *Hub* to remember what users are running and where,
  as well as other information enabling you to restart parts of JupyterHub separately.
- `jupyterhub_cookie_secret` is the encryption key used for securing cookies.
  This file needs to persist in order for restarting the Hub server to avoid invalidating cookies.
  Conversely, deleting this file and restarting the server effectively invalidates all login cookies.
  The cookie secret file is discussed [below](#Security).

The location of these files can be specified via configuration, discussed below.


## How to configure JupyterHub

JupyterHub is configured in two ways:

1. Command-line arguments
2. Configuration files

Type the following for brief information about the command line arguments:

    jupyterhub -h

or:

    jupyterhub --help-all

for the full command line help.

By default, JupyterHub will look for a configuration file (can be missing)
named `jupyterhub_config.py` in the current working directory.
You can create an empty configuration file with


    jupyterhub --generate-config

This empty configuration file has descriptions of all configuration variables and their default values.
You can load a specific config file with:


    jupyterhub -f /path/to/jupyterhub_config.py

See also: [general docs](http://ipython.org/ipython-doc/dev/development/config.html)
on the config system Jupyter uses.


## Networking

In most situations you will want to change the main IP address and port of the Proxy.
This address determines where JupyterHub is available to your users.
The default is all network interfaces (`''`) on port 8000.

This can be done with the following command line arguments:

    jupyterhub --ip=192.168.1.2 --port=443

Or you can put the following lines in a configuration file:

```python
c.JupyterHub.ip = '192.168.1.2'
c.JupyterHub.port = 443
```

Port 443 is used in these examples as it is the default port for SSL/HTTPS.

Configuring only the main IP and port of JupyterHub should be sufficient for most deployments of JupyterHub.
However, for more customized scenarios,
you can configure the following additional networking details.

The Hub service talks to the proxy via a REST API on a secondary port,
whose network interface and port can be configured separately.
By default, this REST API listens on port 8081 of localhost only.
If you want to run the Proxy separate from the Hub,
you may need to configure this IP and port with:

```python
# ideally a private network address
c.JupyterHub.proxy_api_ip = '10.0.1.4'
c.JupyterHub.proxy_api_port = 5432
```

The Hub service also listens only on localhost (port 8080) by default.
The Hub needs needs to be accessible from both the proxy and all Spawners.
When spawning local servers localhost is fine,
but if *either* the Proxy or (more likely) the Spawners will be remote or isolated in containers,
the Hub must listen on an IP that is accessible.

```python
c.JupyterHub.hub_ip = '10.0.1.4'
c.JupyterHub.hub_port = 54321
```

## Security

First of all, since JupyterHub includes authentication and allows arbitrary code execution,
you should not run it without SSL (HTTPS).
This will require you to obtain an official SSL certificate or create a self-signed certificate.
Once you have obtained and installed a key and certificate
you need to pass their locations to JupyterHub's configuration as follows:

```python
c.JupyterHub.ssl_key = '/path/to/my.key'
c.JupyterHub.ssl_cert = '/path/to/my.cert'
```

Some cert files also contain the key, in which case only the cert is needed.
It is important that these files be put in a secure location on your server.

There are two other aspects of JupyterHub network security.

The cookie secret is an encryption key, used to encrypt the cookies used for authentication.
If this value changes for the Hub,
all single-user servers must also be restarted.
Normally, this value is stored in the file `jupyterhub_cookie_secret`,
which can be specified with:

```python
c.JupyterHub.cookie_secret_file = '/path/to/jupyterhub_cookie_secret'
```

In most deployments of JupyterHub, you should point this to a secure location on the file system.
If the cookie secret file doesn't exist when the Hub starts,
a new cookie secret is generated and stored in the file.

If you would like to avoid the need for files,
the value can be loaded in the Hub process from the `JPY_COOKIE_SECRET` env variable:

```bash
export JPY_COOKIE_SECRET=`openssl rand -hex 1024`
```

For security reasons, this env variable should only be visible to the Hub.

The Hub authenticates its requests to the Proxy via an environment variable, `CONFIGPROXY_AUTH_TOKEN`.
If you want to be able to start or restart the proxy or Hub independently of each other (not always necessary),
you must set this environment variable before starting the server (for both the Hub and Proxy):


```bash
export CONFIGPROXY_AUTH_TOKEN=`openssl rand -hex 32`
```

This env variable needs to be visible to the Hub and Proxy.
If you don't set this, the Hub will generate a random key itself,
which means that any time you restart the Hub you **must also restart the Proxy**.
If the proxy is a subprocess of the Hub,
this should happen automatically (this is the default configuration).



## Configuring Authentication

The default Authenticator uses [PAM][] to authenticate system users with their username and password.
The default behavior of this Authenticator is to allow any user with an account and password on the system to login.
You can restrict which users are allowed to login with `Authenticator.whitelist`:


```python
c.Authenticator.whitelist = {'mal', 'zoe', 'inara', 'kaylee'}
```

Admin users of JupyterHub have the ability to take actions on users' behalf,
such as stopping and restarting their servers,
and adding and removing new users from the whitelist.
Any users in the admin list are automatically added to the whitelist,
if they are not already present.
The set of initial Admin users can configured as follows:

```python
c.Authenticator.admin_users = {'mal', 'zoe'}
```

If `JupyterHub.admin_access` is True (not default),
then admin users have permission to log in *as other users* on their respective machines, for debugging.
**You should make sure your users know if admin_access is enabled.**

### Adding and removing users

Users can be added and removed to the Hub via the admin panel or REST API.
These users will be added to the whitelist and database.
Restarting the Hub will not require manually updating the whitelist in your config file,
as the users will be loaded from the database.
This means that after starting the Hub once,
it is not sufficient to remove users from the whitelist in your config file.
You must also remove them from the database, either by discarding the database file,
or via the admin UI.

The default PAMAuthenticator is one case of a special kind of authenticator,
called a LocalAuthenticator,
indicating that it manages users on the local system.
When you add a user to the Hub, a LocalAuthenticator checks if that user already exists.
Normally, there will be an error telling you that the user doesn't exist.
If you set the configuration value


```python
c.LocalAuthenticator.create_system_users = True
```

however, adding a user to the Hub that doesn't already exist on the system
will result in the Hub creating that user via the system `useradd` mechanism.
This option is typically used on hosted deployments of JupyterHub,
to avoid the need to manually create all your users before launching the service.
It is not recommended when running JupyterHub in situations where JupyterHub users maps directly onto UNIX users.


## Configuring single-user servers

Since the single-user server is an instance of `ipython notebook`,
an entire separate multi-process application,
there are many aspect of that server can configure,
and a lot of ways to express that configuration.

At the JupyterHub level, you can set some values on the Spawner.
The simplest of these is `Spawner.notebook_dir`,
which lets you set the root directory for a user's server.
This root notebook directory is the highest level directory users will be able to access in the notebook dashboard.
In this example, the root notebook directory is set to `~/notebooks`,
where `~` is expanded to the user's home directory.

```python
c.Spawner.notebook_dir = '~/notebooks'
```

You can also specify extra command-line arguments to the notebook server with:

```python
c.Spawner.args = ['--debug', '--profile=PHYS131']
```

This could be used to set the users default page for the single user server:

```python
c.Spawner.args = ['--NotebookApp.default_url=/notebooks/Welcome.ipynb']
```

Since the single-user server extends the notebook server application,
it still loads configuration from the `ipython_notebook_config.py` config file.
Each user may have one of these files in `$HOME/.ipython/profile_default/`.
IPython also supports loading system-wide config files from `/etc/ipython/`,
which is the place to put configuration that you want to affect all of your users.

## External services

JupyterHub has a REST API that can be used to run external services.
More detail on this API will be added in the future.

## File locations

It is recommended to put all of the files used by JupyterHub into standard UNIX filesystem locations.

* `/srv/jupyterhub` for all security and runtime files
* `/etc/jupyterhub` for all configuration files
* `/var/log` for log files

## Example

In the following example, we show a configuration files for a fairly standard JupyterHub deployment with the following assumptions:

* JupyterHub is running on a single cloud server
* Using SSL on the standard HTTPS port 443
* You want to use [GitHub OAuth][oauthenticator] for login
* You need the users to exist locally on the server
* You want users' notebooks to be served from `~/assignments` to allow users to browse for notebooks within
  other users home directories
* You want the landing page for each user to be a Welcome.ipynb notebook in their assignments directory.
* All runtime files are put into `/srv/jupyterhub` and log files in `/var/log`.

Let's start out with `jupyterhub_config.py`:

```python
# jupyterhub_config.py
c = get_config()

import os
pjoin = os.path.join

runtime_dir = os.path.join('/srv/jupyterhub')
ssl_dir = pjoin(runtime_dir, 'ssl')
if not os.path.exists(ssl_dir):
    os.makedirs(ssl_dir)


# https on :443
c.JupyterHub.port = 443
c.JupyterHub.ssl_key = pjoin(ssl_dir, 'ssl.key')
c.JupyterHub.ssl_cert = pjoin(ssl_dir, 'ssl.cert')

# put the JupyterHub cookie secret and state db
# in /var/run/jupyterhub
c.JupyterHub.cookie_secret_file = pjoin(runtime_dir, 'cookie_secret')
c.JupyterHub.db_url = pjoin(runtime_dir, 'jupyterhub.sqlite')
# or `--db=/path/to/jupyterhub.sqlite` on the command-line

# put the log file in /var/log
c.JupyterHub.log_file = '/var/log/jupyterhub.log'

# use GitHub OAuthenticator for local users

c.JupyterHub.authenticator_class = 'oauthenticator.LocalGitHubOAuthenticator'
c.GitHubOAuthenticator.oauth_callback_url = os.environ['OAUTH_CALLBACK_URL']
# create system users that don't exist yet
c.LocalAuthenticator.create_system_users = True

# specify users and admin
c.Authenticator.whitelist = {'rgbkrk', 'minrk', 'jhamrick'}
c.Authenticator.admin_users = {'jhamrick', 'rgbkrk'}

# start single-user notebook servers in ~/assignments,
# with ~/assignments/Welcome.ipynb as the default landing page
# this config could also be put in
# /etc/ipython/ipython_notebook_config.py
c.Spawner.notebook_dir = '~/assignments'
c.Spawner.args = ['--NotebookApp.default_url=/notebooks/Welcome.ipynb']
```

Using the GitHub Authenticator [requires a few additional env variables][oauth-setup],
which we will need to set when we launch the server:

```bash
export GITHUB_CLIENT_ID=github_id
export GITHUB_CLIENT_SECRET=github_secret
export OAUTH_CALLBACK_URL=https://example.com/hub/oauth_callback
export CONFIGPROXY_AUTH_TOKEN=super-secret
jupyterhub -f /path/to/aboveconfig.py
```


# Further reading

- TODO: troubleshooting
- [Custom Authenticators](authenticators.md)
- [Custom Spawners](spawners.md)


[oauth-setup]: https://github.com/jupyter/oauthenticator#setup
[oauthenticator]: https://github.com/jupyter/oauthenticator
[PAM]: http://en.wikipedia.org/wiki/Pluggable_authentication_module