```eval_rst
.. _helm-chart-configuration-reference:
```

# Configuration Reference 

The [JupyterHub Helm
chart](https://github.com/jupyterhub/zero-to-jupyterhub-k8s) is configurable by
values in your `config.yaml`. In this way, you can extend user resources, build off
of different Docker images, manage security and authentication, and more.

```eval_rst
Below is a description of the fields that are exposed with the JupyterHub Helm
chart. For more guided information about some specific things you can do with
modifications to the helm chart, see the :ref:`customization-guide`.
```
## scheduling

Objects for customizing the scheduling of various pods on the nodes and
related labels.


### scheduling.userScheduler

The user scheduler is making sure that user pods are scheduled
tight on nodes, this is useful for autoscaling of user node pools.


#### scheduling.userScheduler.image

The image containing the [kube-scheduler
binary](https://console.cloud.google.com/gcr/images/google-containers/GLOBAL/kube-scheduler-amd64).


##### scheduling.userScheduler.image.name

##### scheduling.userScheduler.image.tag

#### scheduling.userScheduler.replicas

You can have multiple schedulers to share the workload or improve
availability on node failure.


#### scheduling.userScheduler.enabled

Enables the user scheduler.


## proxy

### proxy.secretToken

A 32-byte cryptographically secure randomly generated string used to secure communications
between the hub and the configurable-http-proxy.

```sh
# to generate a value, run
openssl rand -hex 32
```

Changing this value will cause the proxy and hub pods to restart. It is good security
practice to rotate these values over time. If this secret leaks, *immediately* change
it to something else, or user data can be compromised


## hub

### hub.labels

Extra labels to add to the hub pod.

See the [Kubernetes docs](https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/)
to learn more about labels.


### hub.db

#### hub.db.type

Type of database backend to use for the hub database.

The Hub requires a persistent database to function, and this lets you specify
where it should be stored.

The various options are:

1. **sqlite-pvc**

   Use an `sqlite` database kept on a persistent volume attached to the hub.

   By default, this disk is created by the cloud provider using
   *dynamic provisioning* configured by a [storage
   class](https://kubernetes.io/docs/concepts/storage/storage-classes/).
   You can customize how this disk is created / attached by
   setting various properties under `hub.db.pvc`.

   This is the default setting, and should work well for most cloud provider
   deployments.

2. **sqlite-memory**

   Use an in-memory `sqlite` database. This should only be used for testing,
   since the database is erased whenever the hub pod restarts - causing the hub
   to lose all memory of users who had logged in before.

   When using this for testing, make sure you delete all other objects that the
   hub has created (such as user pods, user PVCs, etc) every time the hub restarts.
   Otherwise you might run into errors about duplicate resources.

3. **mysql**

   Use an externally hosted mysql database.

   You have to specify an sqlalchemy connection string for the mysql database you
   want to connect to in `hub.db.url` if using this option.

   The general format of the connection string is:
   ```
   mysql+pymysql://<db-username>:<db-password>@<db-hostname>:<db-port>/<db-name>
   ```

   The user specified in the connection string must have the rights to create
   tables in the database specified.

   Note that if you use this, you *must* also set `hub.cookieSecret`.

4. **postgres**

   Use an externally hosted postgres database.

   You have to specify an sqlalchemy connection string for the postgres database you
   want to connect to in `hub.db.url` if using this option.

   The general format of the connection string is:
   ```
   postgres+psycopg2://<db-username>:<db-password>@<db-hostname>:<db-port>/<db-name>
   ```

   The user specified in the connection string must have the rights to create
   tables in the database specified.

   Note that if you use this, you *must* also set `hub.cookieSecret`.


#### hub.db.url

Connection string when `hub.db.type` is mysql or postgres.

See documentation for `hub.db.type` for more details on the format of this property.


#### hub.db.pvc

Customize the Persistent Volume Claim used when `hub.db.type` is `sqlite-pvc`.


##### hub.db.pvc.annotations

Annotations to apply to the PVC containing the sqlite database.

See [the Kubernetes
documentation](https://kubernetes.io/docs/concepts/overview/working-with-objects/annotations/)
for more details about annotations.


##### hub.db.pvc.storage

Size of disk to request for the database disk.


##### hub.db.pvc.selector

Label selectors to set for the PVC containing the sqlite database.

Useful when you are using a specific PV, and want to bind to
that and only that.

See [the Kubernetes
documentation](https://kubernetes.io/docs/concepts/storage/persistent-volumes/#persistentvolumeclaims)
for more details about using a label selector for what PV to
bind to.


### hub.extraEnv

Extra environment variables that should be set for the hub pod.

A list of [EnvVar](https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.9/#envvar-v1-core)
objects.

These are usually used in two circumstances:
  - Passing parameters to some custom code specified with `extraConfig`
  - Passing parameters to an authenticator or spawner that can be directly customized
    by environment variables (rarer)


### hub.cookieSecret

A 32-byte cryptographically secure randomly generated string used to sign values of
secure cookies set by the hub. If unset, jupyterhub will generate one on startup and
save it in the file `jupyterhub_cookie_secret` in the `/srv/jupyterhub` directory of
the hub container. A value set here will make JupyterHub overwrite any previous file.

You do not need to set this at all if you are using the default configuration for
storing databases - sqlite on a persistent volume (with `hub.db.type` set to the
default `sqlite-pvc`). If you are using an external database, then you must set this
value explicitly - or your users will keep getting logged out each time the hub pod
restarts.

Changing this value will all user logins to be invalidated. If this secret leaks,
*immediately* change it to something else, or user data can be compromised

```sh
# to generate a value, run
openssl rand -hex 32
```


### hub.image

Set custom image name / tag for the hub pod.

Use this to customize which hub image is used. Note that you must use a version of
the hub image that was bundled with this particular version of the helm-chart - using
other images might not work.


#### hub.image.name

Name of the image, without the tag.

```
# example names
yuvipanda/wikimedia-hub
gcr.io/my-project/my-hub
```


#### hub.image.tag

The tag of the image to pull.

This is the value after the `:` in your full image name.

```
# example tags
v1.11.1
zhy270a
```


### hub.uid

The UID the hub process should be running as.
Use this only if you are building your own image & know that a user with this uid exists inside the hub container! Advanced feature, handle with care!
Defaults to 1000, which is the uid of the `jovyan` user that is present in the default hub image.

### hub.fsGid

The gid the hub process should be using when touching any volumes mounted.
Use this only if you are building your own image & know that a group with this gid exists inside the hub container! Advanced feature, handle with care!
Defaults to 1000, which is the gid of the `jovyan` user that is present in the default hub image.

### hub.extraConfig

Arbitrary extra python based configuration that should be in `jupyterhub_config.py`.

This is the *escape hatch* - if you want to configure JupyterHub to do something specific
that is not present here as an option, you can just write the raw Python to do it here.

Non-exhaustive examples of things you can do here:
  - Subclass authenticator / spawner to do a custom thing
  - Dynamically launch different images for different sets of images
  - Inject an auth token from GitHub authenticator into user pod
  - Anything else you can think of!

Since this is usually a multi-line string, you want to format it using YAML's
[| operator](http://www.yaml.org/spec/1.2/spec.html#id2795688).

For example:
  ```yaml
  hub:
    extraConfig: |
      c.JupyterHub.something = 'something'
      c.Spawner.somethingelse = 'something else'
  ```

No validation of this python is performed! If you make a mistake here, it will probably
manifest as either the hub pod going into `Error` or `CrashLoopBackoff` states, or in
some special cases, the hub running but... just doing very random things. Be careful!


### hub.imagePullPolicy

Set the imagePullPolicy on the hub pod.

See the [Kubernetes docs](https://kubernetes.io/docs/concepts/containers/images/#updating-images)
for more info on what the values mean.


## singleuser

Options for customizing the environment that is provided to the users after they log in.


### singleuser.cpu

Set CPU limits & guarantees that are enforced for each user.
See: https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/


#### singleuser.cpu.limit

#### singleuser.cpu.guarantee

### singleuser.image

Set custom image name / tag used for spawned users.

This image is used to launch the pod for each user.


#### singleuser.image.name

Name of the image, without the tag.

Examples:
  - yuvipanda/wikimedia-hub-user
  - gcr.io/my-project/my-user-image


#### singleuser.image.tag

The tag of the image to use.

This is the value after the `:` in your full image name.


#### singleuser.image.pullPolicy

Set the imagePullPolicy on the singleuser pods that are spun up by the hub.

See the [Kubernetes docs](https://kubernetes.io/docs/concepts/containers/images/#updating-images)
for more info.


### singleuser.imagePullSecret

Creates an image pull secret for you and makes the user pods utilize
it, allowing them to pull images from private image registries.

Using this configuration option automates the following steps that
normally is required to pull from private image registries.

```sh
# you won't need to run this manually...
kubectl create secret docker-registry singleuser-image-credentials \
  --docker-server=<REGISTRY> \
  --docker-username=<USERNAME> \
  --docker-email=<EMAIL> \
  --docker-password=<PASSWORD>
```

```yaml
# you won't need to specify this manually...
spec:
  imagePullSecrets:
    - name: singleuser-image-credentials
```

To learn the username and password fields to access a gcr.io registry
from a Kubernetes cluster not associated with the same google cloud
credentials, look into [this
guide](http://docs.heptio.com/content/private-registries/pr-gcr.html)
and read the notes about the password.


#### singleuser.imagePullSecret.registry

Name of the private registry you want to create a credential set
for. It will default to Docker Hub's image registry.

Examples:
  - https://index.docker.io/v1/
  - quay.io
  - eu.gcr.io
  - alexmorreale.privatereg.net


#### singleuser.imagePullSecret.username

Name of the user you want to use to connect to your private
registry. For external gcr.io, you will use the `_json_key`.

Examples:
  - alexmorreale
  - alex@pfc.com
  - _json_key


#### singleuser.imagePullSecret.password

Password of the user you want to use to connect to your private
registry.

Examples:
  - plaintextpassword
  - abc123SECRETzyx098

For gcr.io registries the password will be a big JSON blob for a
Google cloud service account, it should look something like below.
              
```yaml
password: |-
  {
    "type": "service_account",
    "project_id": "jupyter-se",
    "private_key_id": "f2ba09118a8d3123b3321bd9a7d6d0d9dc6fdb85",
    ...
  }
```

Learn more in [this
guide](http://docs.heptio.com/content/private-registries/pr-gcr.html).


#### singleuser.imagePullSecret.enabled

Enable the creation of a Kubernetes Secret containing credentials
to access a image registry. By enabling this, user pods and image
puller pods will also be configured to use these credentials when
they pull their container images.


### singleuser.memory

Set Memory limits & guarantees that are enforced for each user.

See the [Kubernetes docs](https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container)
for more info.


#### singleuser.memory.limit

#### singleuser.memory.guarantee

Note that this field is referred to as *requests* by the Kubernetes API.


### singleuser.schedulerStrategy

Deprecated and no longer does anything. Use the user-scheduler instead
in order to accomplish a good packing of the user pods.


## auth

### auth.state

#### auth.state.cryptoKey

auth_state will be encrypted and stored in the Hub’s database. This can include things like authentication tokens, etc. to be passed to Spawners as environment variables.
Encrypting auth_state requires the cryptography package.
It must contain one (or more, separated by ;) 32-byte encryption keys. These can be either base64 or hex-encoded.
The JUPYTERHUB_CRYPT_KEY environment variable for the hub pod is set using this entry.

```sh
# to generate a value, run
openssl rand -hex 32
```

If encryption is unavailable, auth_state cannot be persisted.


#### auth.state.enabled

Enable persisting auth_state (if available).
See: http://jupyterhub.readthedocs.io/en/latest/api/auth.html