# Customizing the User Experience¶

Users, depending on their work needs, require different libraries, packages, and files. Often, users wish to tailor the user environment to meet their personal preferences.

Since JupyterHub can serve many different types of users, JupyterHub managers and administrators must be able to flexibly allocate user resources, like memory or compute. For example, the Hub may be serving power users with large resource requirements as well as beginning users with more basic resource needs. The ability to customize the Hub’s resources to satisfy both user groups improves the user experience for all Hub users.

This page contains instructions for a few common ways you can extend the user experience for your kubernetes deployment. For a list of all the options you can configure with your helm chart, see the Configuration Reference.

## Tailoring the user environment¶

The user environment is the set of packages, environment variables, and various files that are present when the user logs into JupyterHub. The user may also see different tools that provide interfaces to perform specialized tasks, such as RStudio, RISE, JupyterLab, and others.

Usually a docker image specifies the different functionality and things that you wish to provide to users. The following sections will describe how to use existing docker images, how to create custom images, and how to set environment variables.

### Use an existing docker image¶

Using an existing docker image, that someone else has written and maintained, is the simplest approach. For example, Project Jupyter maintains the jupyter/docker-stacks repo, which contains ready to use docker images. Each image includes a set of commonly used science and data science libraries and tools.

The scipy-notebook image, which can be found in the docker-stacks repo, contains useful scientific programming libraries pre-installed. This image may satisfy your needs. If you wish to use an existing image, such as the scipy-notebook image, complete these steps:

1. Modify your config.yaml file to specify the image. For example:

singleuser:
image:
name: jupyter/scipy-notebook
tag: 8e15d329f1e9


Note

Always use an explicit tag, such as a specific commit.

Avoid using latest. Using latest might cause a several minute delay, confusion, or failures for users when a new version of the image is released.

2. Apply the changes by following the directions listed in apply the changes. These directions will pre-pull the image to all the nodes in your cluster. This process may take several minutes to complete.

Note

Docker images must have the jupyterhub package installed within them to be used in this manner.

### Build a custom image with repo2docker¶

If you can’t find a pre-existing image that suits your needs, you can create your own image. The easiest way to do this is with the package repo2docker.

Note

repo2docker lets you quickly convert a GitHub repository into a Docker image that can be used as a base for your JupyterHub instance. Anything inside the GitHub repository will exist in a user’s environment when they join your JupyterHub:

• If you include a requirements.txt file in the root level of the repository, repo2docker will pip install the specified packages into the Docker image to be built.
• If you have an environment.yaml file, conda will create an environment based on this file’s specification.
• If you have a Dockerfile, repo2docker will ignore everything else and just use the Dockerfile.

Below we’ll cover how to use repo2docker to generate a Docker image and how to configure JupyterHub to build off of this image:

2. Install repo2docker using pip:

pip install jupyter-repo2docker


If that command fails due to insufficient permissions, try it with the command option, user:

pip install --user jupyter-repo2docker

3. Create (or find) a GitHub repository you want to use. This repo should have all materials that you want your users to be able to use. You may want to include a pip requirements.txt file to list packages, one per file line, to install such as when using pip install. Specify the versions explicitly so the image is fully reproducible. An example requirements.txt follows:

numpy==1.12.1
scipy==0.19.0
matplotlib==2.0

4. Use repo2docker to build a Docker image.

jupyter-repo2docker <YOUR-GITHUB-REPOSITORY> --image=gcr.io/<PROJECT-NAME>/<IMAGE-NAME>:<TAG> --no-run


This tells repo2docker to fetch master of the GitHub repository, and uses heuristics to build a docker image of it.

Note

• Don’t use underscores in your image name. Other than this, the name can be anything memorable. This bug with underscores will be fixed soon.
• The tag should be the first 6 characters of the SHA in the GitHub commit desired for building the image since this improves reproducibility.
1. Push the newly-built Docker image to the cloud. You can either push this to Docker Hub or to the gcloud docker repository. Here we’ll demonstrate pushing to the gcloud repository:

gcloud docker -- push gcr.io/<project-name>/<image-name>:<tag>

2. Edit the JupyterHub configuration to build from this image. Edit config.yaml file to include these lines in it:

singleuser:
image:
name: gcr.io/<project-name>/<image-name>
tag: <tag>


This step can be done automatically by setting a flag if desired.

3. Tell helm to update JupyterHub to use this configuration. Use the standard method to apply the changes to the config.

4. Restart your notebook if you are already logged in. If you already have a running JupyterHub session, you’ll need to restart it (by stopping and starting your session from the control panel in the top right). New users won’t have to do this.

Note

The contents of your GitHub repository might not show up if you have enabled persistent storage. Disable persistent storage if you want the GitHub repository contents to show up.

5. Enjoy your new computing environment! You should now have a live computing environment built off of the Docker image we’ve created.

### Set environment variables¶

Another way to affect your user’s environment is by setting values for environment variables. While you can set them up in your Docker image, it is often easier to set them up in your helm chart.

To set them up in your helm chart, edit your config.yaml file and apply the changes. For example, this code snippet will set the environment variable EDITOR to the value vim:

singleuser:
extraEnv:
EDITOR: "vim"


You can set any number of static environment variables in the config.yaml file.

Users can read the environment variables in their code in various ways. In Python, for example, the following code will read in an environment variable:

import os
my_value = os.environ["MY_ENVIRONMENT_VARIABLE"]


Other languages will have their own methods of reading these environment variables.

## Allocating and controlling user resources¶

User resources include the CPU, RAM, and Storage which JupyterHub provides to users.

### Set user memory and CPU guarantees / limits¶

Each user on your JupyterHub gets a slice of memory and CPU to use. There are two ways to specify how much users get to use: resource guarantees and resource limits.

A resource guarantee means that all users will have at least this resource available at all times, but they may be given more resources if they’re available. For example, if users are guaranteed 1G of RAM, users can technically use more than 1G of RAM if these resources aren’t being used by other users.

A resource limit sets a hard limit on the resources available. In the example above, if there were a 1G memory limit, it would mean that users could use no more than 1G of RAM, no matter what other resources are being used on the machines.

By default, each user is guaranteed 1G of RAM. All users have at least 1G, but they can technically use more if it is available. You can easily change the amount of these resources, and whether they are a guarantee or a limit, by changing your config.yaml file. This is done with the following structure.

singleuser:
memory:
limit: 1G
guarantee: 1G


This sets a memory limit and guarantee of 1G. Kubernetes will make sure that each user will always have access to 1G of RAM, and requests for more RAM will fail (your kernel will usually die). You can set the limit to be higher than the guarantee to allow some users to use larger amounts of RAM for a very short-term time (e.g. when running a single, short-lived function that consumes a lot of memory).

Similarly, you can limit CPU as follows:

singleuser:
cpu:
limit: .5
guarantee: .5


This would limit your users to a maximum of .5 of a CPU (so 1/2 of a CPU core), as well as guarantee them that same amount.

Note

Remember to apply the changes after changing your config.yaml file!

### Allocate user storage¶

By default, each user receives their own, 10Gi disk for storage when they log in to JupyterHub. This storage can be turned off or changed as described in these sections.

#### Turn off per-user persistent storage¶

If you do not wish for users to have any persistent storage, it can be turned off. Edit the config.yaml file and set the storage type to none:

singleuser:
storage:
type: none


Next apply the changes.

After the changes are applied, new users will no longer be allocated a persistent $HOME directory. Any currently running users will still have access to their storage until their server is restarted. #### Change per-user persistent storage size¶ By default, storage for user home directories are sized to 10Gi each. To increase or decrease this value, edit the config.yaml file: singleuser: storage: capacity: 5Gi  This example will make all new user’s home directories be 5Gi each, instead of the default 10Gi. Important The disks of “logged in” users will not change or be decreased in this example. ## Advanced topic: Pre-populating user’s $HOME directory with notebooks¶

By default, the contents of $HOME in the docker image are hidden by the contents of the per-user persistent volume. If you want to, you can execute a command before the notebook starts each time and copy the files you want from your image to the user’s home directory. If you were using the repo2docker method of building an image and wanted your git repo copied on first use to the user’s home directory, you can use the following in your config.yaml file: singleuser: lifecycleHooks: postStart: exec: command: ["/bin/sh", "-c", "test -f$HOME/.copied || cp -Rf /srv/app/src/. $HOME/; touch$HOME/.copied"]


Note that this will only copy the contents of the directory to \$HOME once - the first time the user logs in. Further updates will not be reflected. There is work in progress for improving this behavior.