Configuration Reference

Important

Make sure the version of JupyterHub for this documentation matches your installation version, as the output of this command may change between versions.

JupyterHub configuration

As explained in the Configuration Basics section, the jupyterhub_config.py can be automatically generated via

jupyterhub --generate-config

The following contains the output of that command for reference.

# Configuration file for jupyterhub.

#------------------------------------------------------------------------------
# Application(SingletonConfigurable) configuration
#------------------------------------------------------------------------------
## This is an application.

## The date format used by logging formatters for %(asctime)s
#  Default: '%Y-%m-%d %H:%M:%S'
# c.Application.log_datefmt = '%Y-%m-%d %H:%M:%S'

## The Logging format template
#  Default: '[%(name)s]%(highlevel)s %(message)s'
# c.Application.log_format = '[%(name)s]%(highlevel)s %(message)s'

## Set the log level by value or name.
#  Choices: any of [0, 10, 20, 30, 40, 50, 'DEBUG', 'INFO', 'WARN', 'ERROR', 'CRITICAL']
#  Default: 30
# c.Application.log_level = 30

## Instead of starting the Application, dump configuration to stdout
#  Default: False
# c.Application.show_config = False

## Instead of starting the Application, dump configuration to stdout (as JSON)
#  Default: False
# c.Application.show_config_json = False

#------------------------------------------------------------------------------
# JupyterHub(Application) configuration
#------------------------------------------------------------------------------
## An Application for starting a Multi-User Jupyter Notebook server.

## Maximum number of concurrent servers that can be active at a time.
#  
#  Setting this can limit the total resources your users can consume.
#  
#  An active server is any server that's not fully stopped. It is considered
#  active from the time it has been requested until the time that it has
#  completely stopped.
#  
#  If this many user servers are active, users will not be able to launch new
#  servers until a server is shutdown. Spawn requests will be rejected with a 429
#  error asking them to try again.
#  
#  If set to 0, no limit is enforced.
#  Default: 0
# c.JupyterHub.active_server_limit = 0

## Duration (in seconds) to determine the number of active users.
#  Default: 1800
# c.JupyterHub.active_user_window = 1800

## Resolution (in seconds) for updating activity
#  
#  If activity is registered that is less than activity_resolution seconds more
#  recent than the current value, the new value will be ignored.
#  
#  This avoids too many writes to the Hub database.
#  Default: 30
# c.JupyterHub.activity_resolution = 30

## Grant admin users permission to access single-user servers.
#  
#  Users should be properly informed if this is enabled.
#  Default: False
# c.JupyterHub.admin_access = False

## DEPRECATED since version 0.7.2, use Authenticator.admin_users instead.
#  Default: set()
# c.JupyterHub.admin_users = set()

## Allow named single-user servers per user
#  Default: False
# c.JupyterHub.allow_named_servers = False

## Answer yes to any questions (e.g. confirm overwrite)
#  Default: False
# c.JupyterHub.answer_yes = False

## PENDING DEPRECATION: consider using services
#  
#  Dict of token:username to be loaded into the database.
#  
#  Allows ahead-of-time generation of API tokens for use by externally managed
#  services, which authenticate as JupyterHub users.
#  
#  Consider using services for general services that talk to the JupyterHub API.
#  Default: {}
# c.JupyterHub.api_tokens = {}

## Authentication for prometheus metrics
#  Default: True
# c.JupyterHub.authenticate_prometheus = True

## Class for authenticating users.
#  
#          This should be a subclass of :class:`jupyterhub.auth.Authenticator`
#  
#          with an :meth:`authenticate` method that:
#  
#          - is a coroutine (asyncio or tornado)
#          - returns username on success, None on failure
#          - takes two arguments: (handler, data),
#            where `handler` is the calling web.RequestHandler,
#            and `data` is the POST form data from the login page.
#  
#          .. versionchanged:: 1.0
#              authenticators may be registered via entry points,
#              e.g. `c.JupyterHub.authenticator_class = 'pam'`
#  
#  Currently installed: 
#    - default: jupyterhub.auth.PAMAuthenticator
#    - dummy: jupyterhub.auth.DummyAuthenticator
#    - pam: jupyterhub.auth.PAMAuthenticator
#  Default: 'jupyterhub.auth.PAMAuthenticator'
# c.JupyterHub.authenticator_class = 'jupyterhub.auth.PAMAuthenticator'

## The base URL of the entire application.
#  
#  Add this to the beginning of all JupyterHub URLs. Use base_url to run
#  JupyterHub within an existing website.
#  
#  .. deprecated: 0.9
#      Use JupyterHub.bind_url
#  Default: '/'
# c.JupyterHub.base_url = '/'

## The public facing URL of the whole JupyterHub application.
#  
#  This is the address on which the proxy will bind. Sets protocol, ip, base_url
#  Default: 'http://:8000'
# c.JupyterHub.bind_url = 'http://:8000'

## Whether to shutdown the proxy when the Hub shuts down.
#  
#  Disable if you want to be able to teardown the Hub while leaving the proxy
#  running.
#  
#  Only valid if the proxy was starting by the Hub process.
#  
#  If both this and cleanup_servers are False, sending SIGINT to the Hub will
#  only shutdown the Hub, leaving everything else running.
#  
#  The Hub should be able to resume from database state.
#  Default: True
# c.JupyterHub.cleanup_proxy = True

## Whether to shutdown single-user servers when the Hub shuts down.
#  
#  Disable if you want to be able to teardown the Hub while leaving the single-
#  user servers running.
#  
#  If both this and cleanup_proxy are False, sending SIGINT to the Hub will only
#  shutdown the Hub, leaving everything else running.
#  
#  The Hub should be able to resume from database state.
#  Default: True
# c.JupyterHub.cleanup_servers = True

## Maximum number of concurrent users that can be spawning at a time.
#  
#  Spawning lots of servers at the same time can cause performance problems for
#  the Hub or the underlying spawning system. Set this limit to prevent bursts of
#  logins from attempting to spawn too many servers at the same time.
#  
#  This does not limit the number of total running servers. See
#  active_server_limit for that.
#  
#  If more than this many users attempt to spawn at a time, their requests will
#  be rejected with a 429 error asking them to try again. Users will have to wait
#  for some of the spawning services to finish starting before they can start
#  their own.
#  
#  If set to 0, no limit is enforced.
#  Default: 100
# c.JupyterHub.concurrent_spawn_limit = 100

## The config file to load
#  Default: 'jupyterhub_config.py'
# c.JupyterHub.config_file = 'jupyterhub_config.py'

## DEPRECATED: does nothing
#  Default: False
# c.JupyterHub.confirm_no_ssl = False

## Number of days for a login cookie to be valid. Default is two weeks.
#  Default: 14
# c.JupyterHub.cookie_max_age_days = 14

## The cookie secret to use to encrypt cookies.
#  
#  Loaded from the JPY_COOKIE_SECRET env variable by default.
#  
#  Should be exactly 256 bits (32 bytes).
#  Default: b''
# c.JupyterHub.cookie_secret = b''

## File in which to store the cookie secret.
#  Default: 'jupyterhub_cookie_secret'
# c.JupyterHub.cookie_secret_file = 'jupyterhub_cookie_secret'

## The location of jupyterhub data files (e.g. /usr/local/share/jupyterhub)
#  Default: '$HOME/checkouts/readthedocs.org/user_builds/jupyterhub/envs/latest/share/jupyterhub'
# c.JupyterHub.data_files_path = '/home/docs/checkouts/readthedocs.org/user_builds/jupyterhub/envs/latest/share/jupyterhub'

## Include any kwargs to pass to the database connection. See
#  sqlalchemy.create_engine for details.
#  Default: {}
# c.JupyterHub.db_kwargs = {}

## url for the database. e.g. `sqlite:///jupyterhub.sqlite`
#  Default: 'sqlite:///jupyterhub.sqlite'
# c.JupyterHub.db_url = 'sqlite:///jupyterhub.sqlite'

## log all database transactions. This has A LOT of output
#  Default: False
# c.JupyterHub.debug_db = False

## DEPRECATED since version 0.8: Use ConfigurableHTTPProxy.debug
#  Default: False
# c.JupyterHub.debug_proxy = False

## If named servers are enabled, default name of server to spawn or open, e.g. by
#  user-redirect.
#  Default: ''
# c.JupyterHub.default_server_name = ''

## The default URL for users when they arrive (e.g. when user directs to "/")
#  
#  By default, redirects users to their own server.
#  
#  Can be a Unicode string (e.g. '/hub/home') or a callable based on the handler
#  object:
#  
#  ::
#  
#      def default_url_fn(handler):
#          user = handler.current_user
#          if user and user.admin:
#              return '/hub/admin'
#          return '/hub/home'
#  
#      c.JupyterHub.default_url = default_url_fn
#  Default: traitlets.Undefined
# c.JupyterHub.default_url = traitlets.Undefined

## Dict authority:dict(files). Specify the key, cert, and/or ca file for an
#  authority. This is useful for externally managed proxies that wish to use
#  internal_ssl.
#  
#  The files dict has this format (you must specify at least a cert)::
#  
#      {
#          'key': '/path/to/key.key',
#          'cert': '/path/to/cert.crt',
#          'ca': '/path/to/ca.crt'
#      }
#  
#  The authorities you can override: 'hub-ca', 'notebooks-ca', 'proxy-api-ca',
#  'proxy-client-ca', and 'services-ca'.
#  
#  Use with internal_ssl
#  Default: {}
# c.JupyterHub.external_ssl_authorities = {}

## Register extra tornado Handlers for jupyterhub.
#  
#  Should be of the form ``("<regex>", Handler)``
#  
#  The Hub prefix will be added, so `/my-page` will be served at `/hub/my-page`.
#  Default: []
# c.JupyterHub.extra_handlers = []

## DEPRECATED: use output redirection instead, e.g.
#  
#  jupyterhub &>> /var/log/jupyterhub.log
#  Default: ''
# c.JupyterHub.extra_log_file = ''

## Extra log handlers to set on JupyterHub logger
#  Default: []
# c.JupyterHub.extra_log_handlers = []

## Generate certs used for internal ssl
#  Default: False
# c.JupyterHub.generate_certs = False

## Generate default config file
#  Default: False
# c.JupyterHub.generate_config = False

## The URL on which the Hub will listen. This is a private URL for internal
#  communication. Typically set in combination with hub_connect_url. If a unix
#  socket, hub_connect_url **must** also be set.
#  
#  For example:
#  
#      "http://127.0.0.1:8081"
#      "unix+http://%2Fsrv%2Fjupyterhub%2Fjupyterhub.sock"
#  
#  .. versionadded:: 0.9
#  Default: ''
# c.JupyterHub.hub_bind_url = ''

## The ip or hostname for proxies and spawners to use for connecting to the Hub.
#  
#  Use when the bind address (`hub_ip`) is 0.0.0.0, :: or otherwise different
#  from the connect address.
#  
#  Default: when `hub_ip` is 0.0.0.0 or ::, use `socket.gethostname()`, otherwise
#  use `hub_ip`.
#  
#  Note: Some spawners or proxy implementations might not support hostnames.
#  Check your spawner or proxy documentation to see if they have extra
#  requirements.
#  
#  .. versionadded:: 0.8
#  Default: ''
# c.JupyterHub.hub_connect_ip = ''

## DEPRECATED
#  
#  Use hub_connect_url
#  
#  .. versionadded:: 0.8
#  
#  .. deprecated:: 0.9
#      Use hub_connect_url
#  Default: 0
# c.JupyterHub.hub_connect_port = 0

## The URL for connecting to the Hub. Spawners, services, and the proxy will use
#  this URL to talk to the Hub.
#  
#  Only needs to be specified if the default hub URL is not connectable (e.g.
#  using a unix+http:// bind url).
#  
#  .. seealso::
#      JupyterHub.hub_connect_ip
#      JupyterHub.hub_bind_url
#  
#  .. versionadded:: 0.9
#  Default: ''
# c.JupyterHub.hub_connect_url = ''

## The ip address for the Hub process to *bind* to.
#  
#  By default, the hub listens on localhost only. This address must be accessible
#  from the proxy and user servers. You may need to set this to a public ip or ''
#  for all interfaces if the proxy or user servers are in containers or on a
#  different host.
#  
#  See `hub_connect_ip` for cases where the bind and connect address should
#  differ, or `hub_bind_url` for setting the full bind URL.
#  Default: '127.0.0.1'
# c.JupyterHub.hub_ip = '127.0.0.1'

## The internal port for the Hub process.
#  
#  This is the internal port of the hub itself. It should never be accessed
#  directly. See JupyterHub.port for the public port to use when accessing
#  jupyterhub. It is rare that this port should be set except in cases of port
#  conflict.
#  
#  See also `hub_ip` for the ip and `hub_bind_url` for setting the full bind URL.
#  Default: 8081
# c.JupyterHub.hub_port = 8081

## Trigger implicit spawns after this many seconds.
#  
#  When a user visits a URL for a server that's not running, they are shown a
#  page indicating that the requested server is not running with a button to
#  spawn the server.
#  
#  Setting this to a positive value will redirect the user after this many
#  seconds, effectively clicking this button automatically for the users,
#  automatically beginning the spawn process.
#  
#  Warning: this can result in errors and surprising behavior when sharing access
#  URLs to actual servers, since the wrong server is likely to be started.
#  Default: 0
# c.JupyterHub.implicit_spawn_seconds = 0

## Timeout (in seconds) to wait for spawners to initialize
#  
#  Checking if spawners are healthy can take a long time if many spawners are
#  active at hub start time.
#  
#  If it takes longer than this timeout to check, init_spawner will be left to
#  complete in the background and the http server is allowed to start.
#  
#  A timeout of -1 means wait forever, which can mean a slow startup of the Hub
#  but ensures that the Hub is fully consistent by the time it starts responding
#  to requests. This matches the behavior of jupyterhub 1.0.
#  
#  .. versionadded: 1.1.0
#  Default: 10
# c.JupyterHub.init_spawners_timeout = 10

## The location to store certificates automatically created by JupyterHub.
#  
#  Use with internal_ssl
#  Default: 'internal-ssl'
# c.JupyterHub.internal_certs_location = 'internal-ssl'

## Enable SSL for all internal communication
#  
#  This enables end-to-end encryption between all JupyterHub components.
#  JupyterHub will automatically create the necessary certificate authority and
#  sign notebook certificates as they're created.
#  Default: False
# c.JupyterHub.internal_ssl = False

## The public facing ip of the whole JupyterHub application (specifically
#  referred to as the proxy).
#  
#  This is the address on which the proxy will listen. The default is to listen
#  on all interfaces. This is the only address through which JupyterHub should be
#  accessed by users.
#  
#  .. deprecated: 0.9
#      Use JupyterHub.bind_url
#  Default: ''
# c.JupyterHub.ip = ''

## Supply extra arguments that will be passed to Jinja environment.
#  Default: {}
# c.JupyterHub.jinja_environment_options = {}

## Interval (in seconds) at which to update last-activity timestamps.
#  Default: 300
# c.JupyterHub.last_activity_interval = 300

## Dict of 'group': ['usernames'] to load at startup.
#  
#  This strictly *adds* groups and users to groups.
#  
#  Loading one set of groups, then starting JupyterHub again with a different set
#  will not remove users or groups from previous launches. That must be done
#  through the API.
#  Default: {}
# c.JupyterHub.load_groups = {}

## The date format used by logging formatters for %(asctime)s
#  See also: Application.log_datefmt
# c.JupyterHub.log_datefmt = '%Y-%m-%d %H:%M:%S'

## The Logging format template
#  See also: Application.log_format
# c.JupyterHub.log_format = '[%(name)s]%(highlevel)s %(message)s'

## Set the log level by value or name.
#  See also: Application.log_level
# c.JupyterHub.log_level = 30

## Specify path to a logo image to override the Jupyter logo in the banner.
#  Default: ''
# c.JupyterHub.logo_file = ''

## Maximum number of concurrent named servers that can be created by a user at a
#  time.
#  
#  Setting this can limit the total resources a user can consume.
#  
#  If set to 0, no limit is enforced.
#  Default: 0
# c.JupyterHub.named_server_limit_per_user = 0

## File to write PID Useful for daemonizing JupyterHub.
#  Default: ''
# c.JupyterHub.pid_file = ''

## The public facing port of the proxy.
#  
#  This is the port on which the proxy will listen. This is the only port through
#  which JupyterHub should be accessed by users.
#  
#  .. deprecated: 0.9
#      Use JupyterHub.bind_url
#  Default: 8000
# c.JupyterHub.port = 8000

## DEPRECATED since version 0.8 : Use ConfigurableHTTPProxy.api_url
#  Default: ''
# c.JupyterHub.proxy_api_ip = ''

## DEPRECATED since version 0.8 : Use ConfigurableHTTPProxy.api_url
#  Default: 0
# c.JupyterHub.proxy_api_port = 0

## DEPRECATED since version 0.8: Use ConfigurableHTTPProxy.auth_token
#  Default: ''
# c.JupyterHub.proxy_auth_token = ''

## Interval (in seconds) at which to check if the proxy is running.
#  Default: 30
# c.JupyterHub.proxy_check_interval = 30

## The class to use for configuring the JupyterHub proxy.
#  
#          Should be a subclass of :class:`jupyterhub.proxy.Proxy`.
#  
#          .. versionchanged:: 1.0
#              proxies may be registered via entry points,
#              e.g. `c.JupyterHub.proxy_class = 'traefik'`
#  
#  Currently installed: 
#    - configurable-http-proxy: jupyterhub.proxy.ConfigurableHTTPProxy
#    - default: jupyterhub.proxy.ConfigurableHTTPProxy
#  Default: 'jupyterhub.proxy.ConfigurableHTTPProxy'
# c.JupyterHub.proxy_class = 'jupyterhub.proxy.ConfigurableHTTPProxy'

## DEPRECATED since version 0.8. Use ConfigurableHTTPProxy.command
#  Default: []
# c.JupyterHub.proxy_cmd = []

## Recreate all certificates used within JupyterHub on restart.
#  
#  Note: enabling this feature requires restarting all notebook servers.
#  
#  Use with internal_ssl
#  Default: False
# c.JupyterHub.recreate_internal_certs = False

## Redirect user to server (if running), instead of control panel.
#  Default: True
# c.JupyterHub.redirect_to_server = True

## Purge and reset the database.
#  Default: False
# c.JupyterHub.reset_db = False

## Interval (in seconds) at which to check connectivity of services with web
#  endpoints.
#  Default: 60
# c.JupyterHub.service_check_interval = 60

## Dict of token:servicename to be loaded into the database.
#  
#  Allows ahead-of-time generation of API tokens for use by externally managed
#  services.
#  Default: {}
# c.JupyterHub.service_tokens = {}

## List of service specification dictionaries.
#  
#  A service
#  
#  For instance::
#  
#      services = [
#          {
#              'name': 'cull_idle',
#              'command': ['/path/to/cull_idle_servers.py'],
#          },
#          {
#              'name': 'formgrader',
#              'url': 'http://127.0.0.1:1234',
#              'api_token': 'super-secret',
#              'environment':
#          }
#      ]
#  Default: []
# c.JupyterHub.services = []

## Instead of starting the Application, dump configuration to stdout
#  See also: Application.show_config
# c.JupyterHub.show_config = False

## Instead of starting the Application, dump configuration to stdout (as JSON)
#  See also: Application.show_config_json
# c.JupyterHub.show_config_json = False

## Shuts down all user servers on logout
#  Default: False
# c.JupyterHub.shutdown_on_logout = False

## The class to use for spawning single-user servers.
#  
#          Should be a subclass of :class:`jupyterhub.spawner.Spawner`.
#  
#          .. versionchanged:: 1.0
#              spawners may be registered via entry points,
#              e.g. `c.JupyterHub.spawner_class = 'localprocess'`
#  
#  Currently installed: 
#    - default: jupyterhub.spawner.LocalProcessSpawner
#    - localprocess: jupyterhub.spawner.LocalProcessSpawner
#    - simple: jupyterhub.spawner.SimpleLocalProcessSpawner
#  Default: 'jupyterhub.spawner.LocalProcessSpawner'
# c.JupyterHub.spawner_class = 'jupyterhub.spawner.LocalProcessSpawner'

## Path to SSL certificate file for the public facing interface of the proxy
#  
#  When setting this, you should also set ssl_key
#  Default: ''
# c.JupyterHub.ssl_cert = ''

## Path to SSL key file for the public facing interface of the proxy
#  
#  When setting this, you should also set ssl_cert
#  Default: ''
# c.JupyterHub.ssl_key = ''

## Host to send statsd metrics to. An empty string (the default) disables sending
#  metrics.
#  Default: ''
# c.JupyterHub.statsd_host = ''

## Port on which to send statsd metrics about the hub
#  Default: 8125
# c.JupyterHub.statsd_port = 8125

## Prefix to use for all metrics sent by jupyterhub to statsd
#  Default: 'jupyterhub'
# c.JupyterHub.statsd_prefix = 'jupyterhub'

## Run single-user servers on subdomains of this host.
#  
#  This should be the full `https://hub.domain.tld[:port]`.
#  
#  Provides additional cross-site protections for javascript served by single-
#  user servers.
#  
#  Requires `<username>.hub.domain.tld` to resolve to the same host as
#  `hub.domain.tld`.
#  
#  In general, this is most easily achieved with wildcard DNS.
#  
#  When using SSL (i.e. always) this also requires a wildcard SSL certificate.
#  Default: ''
# c.JupyterHub.subdomain_host = ''

## Paths to search for jinja templates, before using the default templates.
#  Default: []
# c.JupyterHub.template_paths = []

## Extra variables to be passed into jinja templates
#  Default: {}
# c.JupyterHub.template_vars = {}

## Extra settings overrides to pass to the tornado application.
#  Default: {}
# c.JupyterHub.tornado_settings = {}

## Trust user-provided tokens (via JupyterHub.service_tokens) to have good
#  entropy.
#  
#  If you are not inserting additional tokens via configuration file, this flag
#  has no effect.
#  
#  In JupyterHub 0.8, internally generated tokens do not pass through additional
#  hashing because the hashing is costly and does not increase the entropy of
#  already-good UUIDs.
#  
#  User-provided tokens, on the other hand, are not trusted to have good entropy
#  by default, and are passed through many rounds of hashing to stretch the
#  entropy of the key (i.e. user-provided tokens are treated as passwords instead
#  of random keys). These keys are more costly to check.
#  
#  If your inserted tokens are generated by a good-quality mechanism, e.g.
#  `openssl rand -hex 32`, then you can set this flag to True to reduce the cost
#  of checking authentication tokens.
#  Default: False
# c.JupyterHub.trust_user_provided_tokens = False

## Names to include in the subject alternative name.
#  
#  These names will be used for server name verification. This is useful if
#  JupyterHub is being run behind a reverse proxy or services using ssl are on
#  different hosts.
#  
#  Use with internal_ssl
#  Default: []
# c.JupyterHub.trusted_alt_names = []

## Downstream proxy IP addresses to trust.
#  
#  This sets the list of IP addresses that are trusted and skipped when
#  processing the `X-Forwarded-For` header. For example, if an external proxy is
#  used for TLS termination, its IP address should be added to this list to
#  ensure the correct client IP addresses are recorded in the logs instead of the
#  proxy server's IP address.
#  Default: []
# c.JupyterHub.trusted_downstream_ips = []

## Upgrade the database automatically on start.
#  
#  Only safe if database is regularly backed up. Only SQLite databases will be
#  backed up to a local file automatically.
#  Default: False
# c.JupyterHub.upgrade_db = False

## Callable to affect behavior of /user-redirect/
#  
#  Receives 4 parameters: 1. path - URL path that was provided after /user-
#  redirect/ 2. request - A Tornado HTTPServerRequest representing the current
#  request. 3. user - The currently authenticated user. 4. base_url - The
#  base_url of the current hub, for relative redirects
#  
#  It should return the new URL to redirect to, or None to preserve current
#  behavior.
#  Default: None
# c.JupyterHub.user_redirect_hook = None

#------------------------------------------------------------------------------
# Spawner(LoggingConfigurable) configuration
#------------------------------------------------------------------------------
## Base class for spawning single-user notebook servers.
#  
#  Subclass this, and override the following methods:
#  
#  - load_state - get_state - start - stop - poll
#  
#  As JupyterHub supports multiple users, an instance of the Spawner subclass is
#  created for each user. If there are 20 JupyterHub users, there will be 20
#  instances of the subclass.

## Extra arguments to be passed to the single-user server.
#  
#  Some spawners allow shell-style expansion here, allowing you to use
#  environment variables here. Most, including the default, do not. Consult the
#  documentation for your spawner to verify!
#  Default: []
# c.Spawner.args = []

## An optional hook function that you can implement to pass `auth_state` to the
#  spawner after it has been initialized but before it starts. The `auth_state`
#  dictionary may be set by the `.authenticate()` method of the authenticator.
#  This hook enables you to pass some or all of that information to your spawner.
#  
#  Example::
#  
#      def userdata_hook(spawner, auth_state):
#          spawner.userdata = auth_state["userdata"]
#  
#      c.Spawner.auth_state_hook = userdata_hook
#  Default: None
# c.Spawner.auth_state_hook = None

## The command used for starting the single-user server.
#  
#  Provide either a string or a list containing the path to the startup script
#  command. Extra arguments, other than this path, should be provided via `args`.
#  
#  This is usually set if you want to start the single-user server in a different
#  python environment (with virtualenv/conda) than JupyterHub itself.
#  
#  Some spawners allow shell-style expansion here, allowing you to use
#  environment variables. Most, including the default, do not. Consult the
#  documentation for your spawner to verify!
#  Default: ['jupyterhub-singleuser']
# c.Spawner.cmd = ['jupyterhub-singleuser']

## Maximum number of consecutive failures to allow before shutting down
#  JupyterHub.
#  
#  This helps JupyterHub recover from a certain class of problem preventing
#  launch in contexts where the Hub is automatically restarted (e.g. systemd,
#  docker, kubernetes).
#  
#  A limit of 0 means no limit and consecutive failures will not be tracked.
#  Default: 0
# c.Spawner.consecutive_failure_limit = 0

## Minimum number of cpu-cores a single-user notebook server is guaranteed to
#  have available.
#  
#  If this value is set to 0.5, allows use of 50% of one CPU. If this value is
#  set to 2, allows use of up to 2 CPUs.
#  
#  **This is a configuration setting. Your spawner must implement support for the
#  limit to work.** The default spawner, `LocalProcessSpawner`, does **not**
#  implement this support. A custom spawner **must** add support for this setting
#  for it to be enforced.
#  Default: None
# c.Spawner.cpu_guarantee = None

## Maximum number of cpu-cores a single-user notebook server is allowed to use.
#  
#  If this value is set to 0.5, allows use of 50% of one CPU. If this value is
#  set to 2, allows use of up to 2 CPUs.
#  
#  The single-user notebook server will never be scheduled by the kernel to use
#  more cpu-cores than this. There is no guarantee that it can access this many
#  cpu-cores.
#  
#  **This is a configuration setting. Your spawner must implement support for the
#  limit to work.** The default spawner, `LocalProcessSpawner`, does **not**
#  implement this support. A custom spawner **must** add support for this setting
#  for it to be enforced.
#  Default: None
# c.Spawner.cpu_limit = None

## Enable debug-logging of the single-user server
#  Default: False
# c.Spawner.debug = False

## The URL the single-user server should start in.
#  
#  `{username}` will be expanded to the user's username
#  
#  Example uses:
#  
#  - You can set `notebook_dir` to `/` and `default_url` to `/tree/home/{username}` to allow people to
#    navigate the whole filesystem from their notebook server, but still start in their home directory.
#  - Start with `/notebooks` instead of `/tree` if `default_url` points to a notebook instead of a directory.
#  - You can set this to `/lab` to have JupyterLab start by default, rather than Jupyter Notebook.
#  Default: ''
# c.Spawner.default_url = ''

## Disable per-user configuration of single-user servers.
#  
#  When starting the user's single-user server, any config file found in the
#  user's $HOME directory will be ignored.
#  
#  Note: a user could circumvent this if the user modifies their Python
#  environment, such as when they have their own conda environments / virtualenvs
#  / containers.
#  Default: False
# c.Spawner.disable_user_config = False

## List of environment variables for the single-user server to inherit from the
#  JupyterHub process.
#  
#  This list is used to ensure that sensitive information in the JupyterHub
#  process's environment (such as `CONFIGPROXY_AUTH_TOKEN`) is not passed to the
#  single-user server's process.
#  Default: ['PATH', 'PYTHONPATH', 'CONDA_ROOT', 'CONDA_DEFAULT_ENV', 'VIRTUAL_ENV', 'LANG', 'LC_ALL', 'JUPYTERHUB_SINGLEUSER_APP']
# c.Spawner.env_keep = ['PATH', 'PYTHONPATH', 'CONDA_ROOT', 'CONDA_DEFAULT_ENV', 'VIRTUAL_ENV', 'LANG', 'LC_ALL', 'JUPYTERHUB_SINGLEUSER_APP']

## Extra environment variables to set for the single-user server's process.
#  
#  Environment variables that end up in the single-user server's process come from 3 sources:
#    - This `environment` configurable
#    - The JupyterHub process' environment variables that are listed in `env_keep`
#    - Variables to establish contact between the single-user notebook and the hub (such as JUPYTERHUB_API_TOKEN)
#  
#  The `environment` configurable should be set by JupyterHub administrators to
#  add installation specific environment variables. It is a dict where the key is
#  the name of the environment variable, and the value can be a string or a
#  callable. If it is a callable, it will be called with one parameter (the
#  spawner instance), and should return a string fairly quickly (no blocking
#  operations please!).
#  
#  Note that the spawner class' interface is not guaranteed to be exactly same
#  across upgrades, so if you are using the callable take care to verify it
#  continues to work after upgrades!
#  
#  .. versionchanged:: 1.2
#      environment from this configuration has highest priority,
#      allowing override of 'default' env variables,
#      such as JUPYTERHUB_API_URL.
#  Default: {}
# c.Spawner.environment = {}

## Timeout (in seconds) before giving up on a spawned HTTP server
#  
#  Once a server has successfully been spawned, this is the amount of time we
#  wait before assuming that the server is unable to accept connections.
#  Default: 30
# c.Spawner.http_timeout = 30

## The IP address (or hostname) the single-user server should listen on.
#  
#  The JupyterHub proxy implementation should be able to send packets to this
#  interface.
#  Default: ''
# c.Spawner.ip = ''

## Minimum number of bytes a single-user notebook server is guaranteed to have
#  available.
#  
#  Allows the following suffixes:
#    - K -> Kilobytes
#    - M -> Megabytes
#    - G -> Gigabytes
#    - T -> Terabytes
#  
#  **This is a configuration setting. Your spawner must implement support for the
#  limit to work.** The default spawner, `LocalProcessSpawner`, does **not**
#  implement this support. A custom spawner **must** add support for this setting
#  for it to be enforced.
#  Default: None
# c.Spawner.mem_guarantee = None

## Maximum number of bytes a single-user notebook server is allowed to use.
#  
#  Allows the following suffixes:
#    - K -> Kilobytes
#    - M -> Megabytes
#    - G -> Gigabytes
#    - T -> Terabytes
#  
#  If the single user server tries to allocate more memory than this, it will
#  fail. There is no guarantee that the single-user notebook server will be able
#  to allocate this much memory - only that it can not allocate more than this.
#  
#  **This is a configuration setting. Your spawner must implement support for the
#  limit to work.** The default spawner, `LocalProcessSpawner`, does **not**
#  implement this support. A custom spawner **must** add support for this setting
#  for it to be enforced.
#  Default: None
# c.Spawner.mem_limit = None

## Path to the notebook directory for the single-user server.
#  
#  The user sees a file listing of this directory when the notebook interface is
#  started. The current interface does not easily allow browsing beyond the
#  subdirectories in this directory's tree.
#  
#  `~` will be expanded to the home directory of the user, and {username} will be
#  replaced with the name of the user.
#  
#  Note that this does *not* prevent users from accessing files outside of this
#  path! They can do so with many other means.
#  Default: ''
# c.Spawner.notebook_dir = ''

## An HTML form for options a user can specify on launching their server.
#  
#  The surrounding `<form>` element and the submit button are already provided.
#  
#  For example:
#  
#  .. code:: html
#  
#      Set your key:
#      <input name="key" val="default_key"></input>
#      <br>
#      Choose a letter:
#      <select name="letter" multiple="true">
#        <option value="A">The letter A</option>
#        <option value="B">The letter B</option>
#      </select>
#  
#  The data from this form submission will be passed on to your spawner in
#  `self.user_options`
#  
#  Instead of a form snippet string, this could also be a callable that takes as
#  one parameter the current spawner instance and returns a string. The callable
#  will be called asynchronously if it returns a future, rather than a str. Note
#  that the interface of the spawner class is not deemed stable across versions,
#  so using this functionality might cause your JupyterHub upgrades to break.
#  Default: traitlets.Undefined
# c.Spawner.options_form = traitlets.Undefined

## Interval (in seconds) on which to poll the spawner for single-user server's
#  status.
#  
#  At every poll interval, each spawner's `.poll` method is called, which checks
#  if the single-user server is still running. If it isn't running, then
#  JupyterHub modifies its own state accordingly and removes appropriate routes
#  from the configurable proxy.
#  Default: 30
# c.Spawner.poll_interval = 30

## The port for single-user servers to listen on.
#  
#  Defaults to `0`, which uses a randomly allocated port number each time.
#  
#  If set to a non-zero value, all Spawners will use the same port, which only
#  makes sense if each server is on a different address, e.g. in containers.
#  
#  New in version 0.7.
#  Default: 0
# c.Spawner.port = 0

## An optional hook function that you can implement to do work after the spawner
#  stops.
#  
#  This can be set independent of any concrete spawner implementation.
#  Default: None
# c.Spawner.post_stop_hook = None

## An optional hook function that you can implement to do some bootstrapping work
#  before the spawner starts. For example, create a directory for your user or
#  load initial content.
#  
#  This can be set independent of any concrete spawner implementation.
#  
#  This maybe a coroutine.
#  
#  Example::
#  
#      from subprocess import check_call
#      def my_hook(spawner):
#          username = spawner.user.name
#          check_call(['./examples/bootstrap-script/bootstrap.sh', username])
#  
#      c.Spawner.pre_spawn_hook = my_hook
#  Default: None
# c.Spawner.pre_spawn_hook = None

## List of SSL alt names
#  
#  May be set in config if all spawners should have the same value(s), or set at
#  runtime by Spawner that know their names.
#  Default: []
# c.Spawner.ssl_alt_names = []

## Whether to include DNS:localhost, IP:127.0.0.1 in alt names
#  Default: True
# c.Spawner.ssl_alt_names_include_local = True

## Timeout (in seconds) before giving up on starting of single-user server.
#  
#  This is the timeout for start to return, not the timeout for the server to
#  respond. Callers of spawner.start will assume that startup has failed if it
#  takes longer than this. start should return when the server process is started
#  and its location is known.
#  Default: 60
# c.Spawner.start_timeout = 60

#------------------------------------------------------------------------------
# Authenticator(LoggingConfigurable) configuration
#------------------------------------------------------------------------------
## Base class for implementing an authentication provider for JupyterHub

## Set of users that will have admin rights on this JupyterHub.
#  
#  Admin users have extra privileges:
#   - Use the admin panel to see list of users logged in
#   - Add / remove users in some authenticators
#   - Restart / halt the hub
#   - Start / stop users' single-user servers
#   - Can access each individual users' single-user server (if configured)
#  
#  Admin access should be treated the same way root access is.
#  
#  Defaults to an empty set, in which case no user has admin access.
#  Default: set()
# c.Authenticator.admin_users = set()

## Set of usernames that are allowed to log in.
#  
#  Use this with supported authenticators to restrict which users can log in.
#  This is an additional list that further restricts users, beyond whatever
#  restrictions the authenticator has in place.
#  
#  If empty, does not perform any additional restriction.
#  
#  .. versionchanged:: 1.2
#      `Authenticator.whitelist` renamed to `allowed_users`
#  Default: set()
# c.Authenticator.allowed_users = set()

## The max age (in seconds) of authentication info before forcing a refresh of
#  user auth info.
#  
#  Refreshing auth info allows, e.g. requesting/re-validating auth tokens.
#  
#  See :meth:`.refresh_user` for what happens when user auth info is refreshed
#  (nothing by default).
#  Default: 300
# c.Authenticator.auth_refresh_age = 300

## Automatically begin the login process
#  
#  rather than starting with a "Login with..." link at `/hub/login`
#  
#  To work, `.login_url()` must give a URL other than the default `/hub/login`,
#  such as an oauth handler or another automatic login handler, registered with
#  `.get_handlers()`.
#  
#  .. versionadded:: 0.8
#  Default: False
# c.Authenticator.auto_login = False

## Set of usernames that are not allowed to log in.
#  
#  Use this with supported authenticators to restrict which users can not log in.
#  This is an additional block list that further restricts users, beyond whatever
#  restrictions the authenticator has in place.
#  
#  If empty, does not perform any additional restriction.
#  
#  .. versionadded: 0.9
#  
#  .. versionchanged:: 1.2
#      `Authenticator.blacklist` renamed to `blocked_users`
#  Default: set()
# c.Authenticator.blocked_users = set()

## Delete any users from the database that do not pass validation
#  
#  When JupyterHub starts, `.add_user` will be called on each user in the
#  database to verify that all users are still valid.
#  
#  If `delete_invalid_users` is True, any users that do not pass validation will
#  be deleted from the database. Use this if users might be deleted from an
#  external system, such as local user accounts.
#  
#  If False (default), invalid users remain in the Hub's database and a warning
#  will be issued. This is the default to avoid data loss due to config changes.
#  Default: False
# c.Authenticator.delete_invalid_users = False

## Enable persisting auth_state (if available).
#  
#  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.
#  
#  Additionally, the JUPYTERHUB_CRYPT_KEY environment variable must contain one
#  (or more, separated by ;) 32B encryption keys. These can be either base64 or
#  hex-encoded.
#  
#  If encryption is unavailable, auth_state cannot be persisted.
#  
#  New in JupyterHub 0.8
#  Default: False
# c.Authenticator.enable_auth_state = False

## An optional hook function that you can implement to do some bootstrapping work
#  during authentication. For example, loading user account details from an
#  external system.
#  
#  This function is called after the user has passed all authentication checks
#  and is ready to successfully authenticate. This function must return the
#  authentication dict reguardless of changes to it.
#  
#  This maybe a coroutine.
#  
#  .. versionadded: 1.0
#  
#  Example::
#  
#      import os, pwd
#      def my_hook(authenticator, handler, authentication):
#          user_data = pwd.getpwnam(authentication['name'])
#          spawn_data = {
#              'pw_data': user_data
#              'gid_list': os.getgrouplist(authentication['name'], user_data.pw_gid)
#          }
#  
#          if authentication['auth_state'] is None:
#              authentication['auth_state'] = {}
#          authentication['auth_state']['spawn_data'] = spawn_data
#  
#          return authentication
#  
#      c.Authenticator.post_auth_hook = my_hook
#  Default: None
# c.Authenticator.post_auth_hook = None

## Force refresh of auth prior to spawn.
#  
#  This forces :meth:`.refresh_user` to be called prior to launching a server, to
#  ensure that auth state is up-to-date.
#  
#  This can be important when e.g. auth tokens that may have expired are passed
#  to the spawner via environment variables from auth_state.
#  
#  If refresh_user cannot refresh the user auth data, launch will fail until the
#  user logs in again.
#  Default: False
# c.Authenticator.refresh_pre_spawn = False

## Dictionary mapping authenticator usernames to JupyterHub users.
#  
#  Primarily used to normalize OAuth user names to local users.
#  Default: {}
# c.Authenticator.username_map = {}

## Regular expression pattern that all valid usernames must match.
#  
#  If a username does not match the pattern specified here, authentication will
#  not be attempted.
#  
#  If not set, allow any username.
#  Default: ''
# c.Authenticator.username_pattern = ''

## Deprecated, use `Authenticator.allowed_users`
#  Default: set()
# c.Authenticator.whitelist = set()

#------------------------------------------------------------------------------
# CryptKeeper(SingletonConfigurable) configuration
#------------------------------------------------------------------------------
## Encapsulate encryption configuration
#  
#  Use via the encryption_config singleton below.

#  Default: []
# c.CryptKeeper.keys = []

## The number of threads to allocate for encryption
#  Default: 1
# c.CryptKeeper.n_threads = 1

JupyterHub help command output

This section contains the output of the command jupyterhub --help-all.

Start a multi-user Jupyter Notebook server

Spawns a configurable-http-proxy and multi-user Hub, which authenticates users
and spawns single-user Notebook servers on behalf of users.

Subcommands
===========
Subcommands are launched as `jupyterhub cmd [args]`. For information on using
subcommand 'cmd', do: `jupyterhub cmd -h`.

token
    Generate an API token for a user
upgrade-db
    Upgrade your JupyterHub state database to the current version.

Options
=======
The options below are convenience aliases to configurable class-options,
as listed in the "Equivalent to" description-line of the aliases.
To see all configurable class-options for some <cmd>, use:
    <cmd> --help-all

--debug
    set log level to logging.DEBUG (maximize logging output)
    Equivalent to: [--Application.log_level=10]
--generate-config
    generate default config file
    Equivalent to: [--JupyterHub.generate_config=True]
--generate-certs
    generate certificates used for internal ssl
    Equivalent to: [--JupyterHub.generate_certs=True]
--no-db
    disable persisting state database to disk
    Equivalent to: [--JupyterHub.db_url=sqlite:///:memory:]
--upgrade-db
    Automatically upgrade the database if needed on startup.
    
    Only safe if the database has been backed up.
    Only SQLite database files will be backed up automatically.
    Equivalent to: [--JupyterHub.upgrade_db=True]
--no-ssl
    [DEPRECATED in 0.7: does nothing]
    Equivalent to: [--JupyterHub.confirm_no_ssl=True]
--base-url=<URLPrefix>
    The base URL of the entire application.
    Add this to the beginning of all JupyterHub URLs. Use base_url to run
    JupyterHub within an existing website.
    .. deprecated: 0.9
        Use JupyterHub.bind_url
    Default: '/'
    Equivalent to: [--JupyterHub.base_url]
-y=<Bool>
    Answer yes to any questions (e.g. confirm overwrite)
    Default: False
    Equivalent to: [--JupyterHub.answer_yes]
--ssl-key=<Unicode>
    Path to SSL key file for the public facing interface of the proxy
    When setting this, you should also set ssl_cert
    Default: ''
    Equivalent to: [--JupyterHub.ssl_key]
--ssl-cert=<Unicode>
    Path to SSL certificate file for the public facing interface of the proxy
    When setting this, you should also set ssl_key
    Default: ''
    Equivalent to: [--JupyterHub.ssl_cert]
--url=<Unicode>
    The public facing URL of the whole JupyterHub application.
    This is the address on which the proxy will bind. Sets protocol, ip,
    base_url
    Default: 'http://:8000'
    Equivalent to: [--JupyterHub.bind_url]
--ip=<Unicode>
    The public facing ip of the whole JupyterHub application (specifically
    referred to as the proxy).
    This is the address on which the proxy will listen. The default is to listen
    on all interfaces. This is the only address through which JupyterHub should
    be accessed by users.
    .. deprecated: 0.9
        Use JupyterHub.bind_url
    Default: ''
    Equivalent to: [--JupyterHub.ip]
--port=<Int>
    The public facing port of the proxy.
    This is the port on which the proxy will listen. This is the only port
    through which JupyterHub should be accessed by users.
    .. deprecated: 0.9
        Use JupyterHub.bind_url
    Default: 8000
    Equivalent to: [--JupyterHub.port]
--pid-file=<Unicode>
    File to write PID Useful for daemonizing JupyterHub.
    Default: ''
    Equivalent to: [--JupyterHub.pid_file]
--log-file=<Unicode>
    DEPRECATED: use output redirection instead, e.g.
    jupyterhub &>> /var/log/jupyterhub.log
    Default: ''
    Equivalent to: [--JupyterHub.extra_log_file]
--log-level=<Enum>
    Set the log level by value or name.
    Choices: any of [0, 10, 20, 30, 40, 50, 'DEBUG', 'INFO', 'WARN', 'ERROR', 'CRITICAL']
    Default: 30
    Equivalent to: [--Application.log_level]
-f=<Unicode>
    The config file to load
    Default: 'jupyterhub_config.py'
    Equivalent to: [--JupyterHub.config_file]
--config=<Unicode>
    The config file to load
    Default: 'jupyterhub_config.py'
    Equivalent to: [--JupyterHub.config_file]
--db=<Unicode>
    url for the database. e.g. `sqlite:///jupyterhub.sqlite`
    Default: 'sqlite:///jupyterhub.sqlite'
    Equivalent to: [--JupyterHub.db_url]

Class options
=============
The command-line option below sets the respective configurable class-parameter:
    --Class.parameter=value
This line is evaluated in Python, so simple expressions are allowed.
For instance, to set `C.a=[0,1,2]`, you may type this:
    --C.a='range(3)'

Application(SingletonConfigurable) options
------------------------------------------
--Application.log_datefmt=<Unicode>
    The date format used by logging formatters for %(asctime)s
    Default: '%Y-%m-%d %H:%M:%S'
--Application.log_format=<Unicode>
    The Logging format template
    Default: '[%(name)s]%(highlevel)s %(message)s'
--Application.log_level=<Enum>
    Set the log level by value or name.
    Choices: any of [0, 10, 20, 30, 40, 50, 'DEBUG', 'INFO', 'WARN', 'ERROR', 'CRITICAL']
    Default: 30
--Application.show_config=<Bool>
    Instead of starting the Application, dump configuration to stdout
    Default: False
--Application.show_config_json=<Bool>
    Instead of starting the Application, dump configuration to stdout (as JSON)
    Default: False

JupyterHub(Application) options
-------------------------------
--JupyterHub.active_server_limit=<Int>
    Maximum number of concurrent servers that can be active at a time.
    Setting this can limit the total resources your users can consume.
    An active server is any server that's not fully stopped. It is considered
    active from the time it has been requested until the time that it has
    completely stopped.
    If this many user servers are active, users will not be able to launch new
    servers until a server is shutdown. Spawn requests will be rejected with a
    429 error asking them to try again.
    If set to 0, no limit is enforced.
    Default: 0
--JupyterHub.active_user_window=<Int>
    Duration (in seconds) to determine the number of active users.
    Default: 1800
--JupyterHub.activity_resolution=<Int>
    Resolution (in seconds) for updating activity
    If activity is registered that is less than activity_resolution seconds more
    recent than the current value, the new value will be ignored.
    This avoids too many writes to the Hub database.
    Default: 30
--JupyterHub.admin_access=<Bool>
    Grant admin users permission to access single-user servers.
    Users should be properly informed if this is enabled.
    Default: False
--JupyterHub.admin_users=<set-item-1>...
    DEPRECATED since version 0.7.2, use Authenticator.admin_users instead.
    Default: set()
--JupyterHub.allow_named_servers=<Bool>
    Allow named single-user servers per user
    Default: False
--JupyterHub.answer_yes=<Bool>
    Answer yes to any questions (e.g. confirm overwrite)
    Default: False
--JupyterHub.api_tokens=<key-1>=<value-1>...
    PENDING DEPRECATION: consider using services
    Dict of token:username to be loaded into the database.
    Allows ahead-of-time generation of API tokens for use by externally managed
    services, which authenticate as JupyterHub users.
    Consider using services for general services that talk to the JupyterHub
    API.
    Default: {}
--JupyterHub.authenticate_prometheus=<Bool>
    Authentication for prometheus metrics
    Default: True
--JupyterHub.authenticator_class=<EntryPointType>
    Class for authenticating users.
            This should be a subclass of :class:`jupyterhub.auth.Authenticator`
            with an :meth:`authenticate` method that:
            - is a coroutine (asyncio or tornado)
            - returns username on success, None on failure
            - takes two arguments: (handler, data),
              where `handler` is the calling web.RequestHandler,
              and `data` is the POST form data from the login page.
            .. versionchanged:: 1.0
                authenticators may be registered via entry points,
                e.g. `c.JupyterHub.authenticator_class = 'pam'`
    Currently installed: 
      - default: jupyterhub.auth.PAMAuthenticator
      - dummy: jupyterhub.auth.DummyAuthenticator
      - pam: jupyterhub.auth.PAMAuthenticator
    Default: 'jupyterhub.auth.PAMAuthenticator'
--JupyterHub.base_url=<URLPrefix>
    The base URL of the entire application.
    Add this to the beginning of all JupyterHub URLs. Use base_url to run
    JupyterHub within an existing website.
    .. deprecated: 0.9
        Use JupyterHub.bind_url
    Default: '/'
--JupyterHub.bind_url=<Unicode>
    The public facing URL of the whole JupyterHub application.
    This is the address on which the proxy will bind. Sets protocol, ip,
    base_url
    Default: 'http://:8000'
--JupyterHub.cleanup_proxy=<Bool>
    Whether to shutdown the proxy when the Hub shuts down.
    Disable if you want to be able to teardown the Hub while leaving the proxy
    running.
    Only valid if the proxy was starting by the Hub process.
    If both this and cleanup_servers are False, sending SIGINT to the Hub will
    only shutdown the Hub, leaving everything else running.
    The Hub should be able to resume from database state.
    Default: True
--JupyterHub.cleanup_servers=<Bool>
    Whether to shutdown single-user servers when the Hub shuts down.
    Disable if you want to be able to teardown the Hub while leaving the single-
    user servers running.
    If both this and cleanup_proxy are False, sending SIGINT to the Hub will
    only shutdown the Hub, leaving everything else running.
    The Hub should be able to resume from database state.
    Default: True
--JupyterHub.concurrent_spawn_limit=<Int>
    Maximum number of concurrent users that can be spawning at a time.
    Spawning lots of servers at the same time can cause performance problems for
    the Hub or the underlying spawning system. Set this limit to prevent bursts
    of logins from attempting to spawn too many servers at the same time.
    This does not limit the number of total running servers. See
    active_server_limit for that.
    If more than this many users attempt to spawn at a time, their requests will
    be rejected with a 429 error asking them to try again. Users will have to
    wait for some of the spawning services to finish starting before they can
    start their own.
    If set to 0, no limit is enforced.
    Default: 100
--JupyterHub.config_file=<Unicode>
    The config file to load
    Default: 'jupyterhub_config.py'
--JupyterHub.confirm_no_ssl=<Bool>
    DEPRECATED: does nothing
    Default: False
--JupyterHub.cookie_max_age_days=<Float>
    Number of days for a login cookie to be valid. Default is two weeks.
    Default: 14
--JupyterHub.cookie_secret=<Bytes>
    The cookie secret to use to encrypt cookies.
    Loaded from the JPY_COOKIE_SECRET env variable by default.
    Should be exactly 256 bits (32 bytes).
    Default: b''
--JupyterHub.cookie_secret_file=<Unicode>
    File in which to store the cookie secret.
    Default: 'jupyterhub_cookie_secret'
--JupyterHub.data_files_path=<Unicode>
    The location of jupyterhub data files (e.g. /usr/local/share/jupyterhub)
    Default: '$HOME/checkouts/readthedocs.org/user_builds/jupyterhub/...
--JupyterHub.db_kwargs=<key-1>=<value-1>...
    Include any kwargs to pass to the database connection. See
    sqlalchemy.create_engine for details.
    Default: {}
--JupyterHub.db_url=<Unicode>
    url for the database. e.g. `sqlite:///jupyterhub.sqlite`
    Default: 'sqlite:///jupyterhub.sqlite'
--JupyterHub.debug_db=<Bool>
    log all database transactions. This has A LOT of output
    Default: False
--JupyterHub.debug_proxy=<Bool>
    DEPRECATED since version 0.8: Use ConfigurableHTTPProxy.debug
    Default: False
--JupyterHub.default_server_name=<Unicode>
    If named servers are enabled, default name of server to spawn or open, e.g.
    by user-redirect.
    Default: ''
--JupyterHub.default_url=<Union>
    The default URL for users when they arrive (e.g. when user directs to "/")
    By default, redirects users to their own server.
    Can be a Unicode string (e.g. '/hub/home') or a callable based on the
    handler object:
    ::
        def default_url_fn(handler):
            user = handler.current_user
            if user and user.admin:
                return '/hub/admin'
            return '/hub/home'
        c.JupyterHub.default_url = default_url_fn
    Default: traitlets.Undefined
--JupyterHub.external_ssl_authorities=<key-1>=<value-1>...
    Dict authority:dict(files). Specify the key, cert, and/or ca file for an
    authority. This is useful for externally managed proxies that wish to use
    internal_ssl.
    The files dict has this format (you must specify at least a cert)::
        {
            'key': '/path/to/key.key',
            'cert': '/path/to/cert.crt',
            'ca': '/path/to/ca.crt'
        }
    The authorities you can override: 'hub-ca', 'notebooks-ca', 'proxy-api-ca',
    'proxy-client-ca', and 'services-ca'.
    Use with internal_ssl
    Default: {}
--JupyterHub.extra_handlers=<list-item-1>...
    Register extra tornado Handlers for jupyterhub.
    Should be of the form ``("<regex>", Handler)``
    The Hub prefix will be added, so `/my-page` will be served at `/hub/my-
    page`.
    Default: []
--JupyterHub.extra_log_file=<Unicode>
    DEPRECATED: use output redirection instead, e.g.
    jupyterhub &>> /var/log/jupyterhub.log
    Default: ''
--JupyterHub.extra_log_handlers=<list-item-1>...
    Extra log handlers to set on JupyterHub logger
    Default: []
--JupyterHub.generate_certs=<Bool>
    Generate certs used for internal ssl
    Default: False
--JupyterHub.generate_config=<Bool>
    Generate default config file
    Default: False
--JupyterHub.hub_bind_url=<Unicode>
    The URL on which the Hub will listen. This is a private URL for internal
    communication. Typically set in combination with hub_connect_url. If a unix
    socket, hub_connect_url **must** also be set.
    For example:
        "http://127.0.0.1:8081"
        "unix+http://%2Fsrv%2Fjupyterhub%2Fjupyterhub.sock"
    .. versionadded:: 0.9
    Default: ''
--JupyterHub.hub_connect_ip=<Unicode>
    The ip or hostname for proxies and spawners to use for connecting to the
    Hub.
    Use when the bind address (`hub_ip`) is 0.0.0.0, :: or otherwise different
    from the connect address.
    Default: when `hub_ip` is 0.0.0.0 or ::, use `socket.gethostname()`,
    otherwise use `hub_ip`.
    Note: Some spawners or proxy implementations might not support hostnames.
    Check your spawner or proxy documentation to see if they have extra
    requirements.
    .. versionadded:: 0.8
    Default: ''
--JupyterHub.hub_connect_port=<Int>
    DEPRECATED
    Use hub_connect_url
    .. versionadded:: 0.8
    .. deprecated:: 0.9
        Use hub_connect_url
    Default: 0
--JupyterHub.hub_connect_url=<Unicode>
    The URL for connecting to the Hub. Spawners, services, and the proxy will
    use this URL to talk to the Hub.
    Only needs to be specified if the default hub URL is not connectable (e.g.
    using a unix+http:// bind url).
    .. seealso::
        JupyterHub.hub_connect_ip
        JupyterHub.hub_bind_url
    .. versionadded:: 0.9
    Default: ''
--JupyterHub.hub_ip=<Unicode>
    The ip address for the Hub process to *bind* to.
    By default, the hub listens on localhost only. This address must be
    accessible from the proxy and user servers. You may need to set this to a
    public ip or '' for all interfaces if the proxy or user servers are in
    containers or on a different host.
    See `hub_connect_ip` for cases where the bind and connect address should
    differ, or `hub_bind_url` for setting the full bind URL.
    Default: '127.0.0.1'
--JupyterHub.hub_port=<Int>
    The internal port for the Hub process.
    This is the internal port of the hub itself. It should never be accessed
    directly. See JupyterHub.port for the public port to use when accessing
    jupyterhub. It is rare that this port should be set except in cases of port
    conflict.
    See also `hub_ip` for the ip and `hub_bind_url` for setting the full bind
    URL.
    Default: 8081
--JupyterHub.implicit_spawn_seconds=<Float>
    Trigger implicit spawns after this many seconds.
    When a user visits a URL for a server that's not running, they are shown a
    page indicating that the requested server is not running with a button to
    spawn the server.
    Setting this to a positive value will redirect the user after this many
    seconds, effectively clicking this button automatically for the users,
    automatically beginning the spawn process.
    Warning: this can result in errors and surprising behavior when sharing
    access URLs to actual servers, since the wrong server is likely to be
    started.
    Default: 0
--JupyterHub.init_spawners_timeout=<Int>
    Timeout (in seconds) to wait for spawners to initialize
    Checking if spawners are healthy can take a long time if many spawners are
    active at hub start time.
    If it takes longer than this timeout to check, init_spawner will be left to
    complete in the background and the http server is allowed to start.
    A timeout of -1 means wait forever, which can mean a slow startup of the Hub
    but ensures that the Hub is fully consistent by the time it starts
    responding to requests. This matches the behavior of jupyterhub 1.0.
    .. versionadded: 1.1.0
    Default: 10
--JupyterHub.internal_certs_location=<Unicode>
    The location to store certificates automatically created by JupyterHub.
    Use with internal_ssl
    Default: 'internal-ssl'
--JupyterHub.internal_ssl=<Bool>
    Enable SSL for all internal communication
    This enables end-to-end encryption between all JupyterHub components.
    JupyterHub will automatically create the necessary certificate authority and
    sign notebook certificates as they're created.
    Default: False
--JupyterHub.ip=<Unicode>
    The public facing ip of the whole JupyterHub application (specifically
    referred to as the proxy).
    This is the address on which the proxy will listen. The default is to listen
    on all interfaces. This is the only address through which JupyterHub should
    be accessed by users.
    .. deprecated: 0.9
        Use JupyterHub.bind_url
    Default: ''
--JupyterHub.jinja_environment_options=<key-1>=<value-1>...
    Supply extra arguments that will be passed to Jinja environment.
    Default: {}
--JupyterHub.last_activity_interval=<Int>
    Interval (in seconds) at which to update last-activity timestamps.
    Default: 300
--JupyterHub.load_groups=<key-1>=<value-1>...
    Dict of 'group': ['usernames'] to load at startup.
    This strictly *adds* groups and users to groups.
    Loading one set of groups, then starting JupyterHub again with a different
    set will not remove users or groups from previous launches. That must be
    done through the API.
    Default: {}
--JupyterHub.log_datefmt=<Unicode>
    The date format used by logging formatters for %(asctime)s
    Default: '%Y-%m-%d %H:%M:%S'
--JupyterHub.log_format=<Unicode>
    The Logging format template
    Default: '[%(name)s]%(highlevel)s %(message)s'
--JupyterHub.log_level=<Enum>
    Set the log level by value or name.
    Choices: any of [0, 10, 20, 30, 40, 50, 'DEBUG', 'INFO', 'WARN', 'ERROR', 'CRITICAL']
    Default: 30
--JupyterHub.logo_file=<Unicode>
    Specify path to a logo image to override the Jupyter logo in the banner.
    Default: ''
--JupyterHub.named_server_limit_per_user=<Int>
    Maximum number of concurrent named servers that can be created by a user at
    a time.
    Setting this can limit the total resources a user can consume.
    If set to 0, no limit is enforced.
    Default: 0
--JupyterHub.pid_file=<Unicode>
    File to write PID Useful for daemonizing JupyterHub.
    Default: ''
--JupyterHub.port=<Int>
    The public facing port of the proxy.
    This is the port on which the proxy will listen. This is the only port
    through which JupyterHub should be accessed by users.
    .. deprecated: 0.9
        Use JupyterHub.bind_url
    Default: 8000
--JupyterHub.proxy_api_ip=<Unicode>
    DEPRECATED since version 0.8 : Use ConfigurableHTTPProxy.api_url
    Default: ''
--JupyterHub.proxy_api_port=<Int>
    DEPRECATED since version 0.8 : Use ConfigurableHTTPProxy.api_url
    Default: 0
--JupyterHub.proxy_auth_token=<Unicode>
    DEPRECATED since version 0.8: Use ConfigurableHTTPProxy.auth_token
    Default: ''
--JupyterHub.proxy_check_interval=<Int>
    Interval (in seconds) at which to check if the proxy is running.
    Default: 30
--JupyterHub.proxy_class=<EntryPointType>
    The class to use for configuring the JupyterHub proxy.
            Should be a subclass of :class:`jupyterhub.proxy.Proxy`.
            .. versionchanged:: 1.0
                proxies may be registered via entry points,
                e.g. `c.JupyterHub.proxy_class = 'traefik'`
    Currently installed: 
      - configurable-http-proxy: jupyterhub.proxy.ConfigurableHTTPProxy
      - default: jupyterhub.proxy.ConfigurableHTTPProxy
    Default: 'jupyterhub.proxy.ConfigurableHTTPProxy'
--JupyterHub.proxy_cmd=<command-item-1>...
    DEPRECATED since version 0.8. Use ConfigurableHTTPProxy.command
    Default: []
--JupyterHub.recreate_internal_certs=<Bool>
    Recreate all certificates used within JupyterHub on restart.
    Note: enabling this feature requires restarting all notebook servers.
    Use with internal_ssl
    Default: False
--JupyterHub.redirect_to_server=<Bool>
    Redirect user to server (if running), instead of control panel.
    Default: True
--JupyterHub.reset_db=<Bool>
    Purge and reset the database.
    Default: False
--JupyterHub.service_check_interval=<Int>
    Interval (in seconds) at which to check connectivity of services with web
    endpoints.
    Default: 60
--JupyterHub.service_tokens=<key-1>=<value-1>...
    Dict of token:servicename to be loaded into the database.
    Allows ahead-of-time generation of API tokens for use by externally managed
    services.
    Default: {}
--JupyterHub.services=<list-item-1>...
    List of service specification dictionaries.
    A service
    For instance::
        services = [
            {
                'name': 'cull_idle',
                'command': ['/path/to/cull_idle_servers.py'],
            },
            {
                'name': 'formgrader',
                'url': 'http://127.0.0.1:1234',
                'api_token': 'super-secret',
                'environment':
            }
        ]
    Default: []
--JupyterHub.show_config=<Bool>
    Instead of starting the Application, dump configuration to stdout
    Default: False
--JupyterHub.show_config_json=<Bool>
    Instead of starting the Application, dump configuration to stdout (as JSON)
    Default: False
--JupyterHub.shutdown_on_logout=<Bool>
    Shuts down all user servers on logout
    Default: False
--JupyterHub.spawner_class=<EntryPointType>
    The class to use for spawning single-user servers.
            Should be a subclass of :class:`jupyterhub.spawner.Spawner`.
            .. versionchanged:: 1.0
                spawners may be registered via entry points,
                e.g. `c.JupyterHub.spawner_class = 'localprocess'`
    Currently installed: 
      - default: jupyterhub.spawner.LocalProcessSpawner
      - localprocess: jupyterhub.spawner.LocalProcessSpawner
      - simple: jupyterhub.spawner.SimpleLocalProcessSpawner
    Default: 'jupyterhub.spawner.LocalProcessSpawner'
--JupyterHub.ssl_cert=<Unicode>
    Path to SSL certificate file for the public facing interface of the proxy
    When setting this, you should also set ssl_key
    Default: ''
--JupyterHub.ssl_key=<Unicode>
    Path to SSL key file for the public facing interface of the proxy
    When setting this, you should also set ssl_cert
    Default: ''
--JupyterHub.statsd_host=<Unicode>
    Host to send statsd metrics to. An empty string (the default) disables
    sending metrics.
    Default: ''
--JupyterHub.statsd_port=<Int>
    Port on which to send statsd metrics about the hub
    Default: 8125
--JupyterHub.statsd_prefix=<Unicode>
    Prefix to use for all metrics sent by jupyterhub to statsd
    Default: 'jupyterhub'
--JupyterHub.subdomain_host=<Unicode>
    Run single-user servers on subdomains of this host.
    This should be the full `https://hub.domain.tld[:port]`.
    Provides additional cross-site protections for javascript served by single-
    user servers.
    Requires `<username>.hub.domain.tld` to resolve to the same host as
    `hub.domain.tld`.
    In general, this is most easily achieved with wildcard DNS.
    When using SSL (i.e. always) this also requires a wildcard SSL certificate.
    Default: ''
--JupyterHub.template_paths=<list-item-1>...
    Paths to search for jinja templates, before using the default templates.
    Default: []
--JupyterHub.template_vars=<key-1>=<value-1>...
    Extra variables to be passed into jinja templates
    Default: {}
--JupyterHub.tornado_settings=<key-1>=<value-1>...
    Extra settings overrides to pass to the tornado application.
    Default: {}
--JupyterHub.trust_user_provided_tokens=<Bool>
    Trust user-provided tokens (via JupyterHub.service_tokens) to have good
    entropy.
    If you are not inserting additional tokens via configuration file, this flag
    has no effect.
    In JupyterHub 0.8, internally generated tokens do not pass through
    additional hashing because the hashing is costly and does not increase the
    entropy of already-good UUIDs.
    User-provided tokens, on the other hand, are not trusted to have good
    entropy by default, and are passed through many rounds of hashing to stretch
    the entropy of the key (i.e. user-provided tokens are treated as passwords
    instead of random keys). These keys are more costly to check.
    If your inserted tokens are generated by a good-quality mechanism, e.g.
    `openssl rand -hex 32`, then you can set this flag to True to reduce the
    cost of checking authentication tokens.
    Default: False
--JupyterHub.trusted_alt_names=<list-item-1>...
    Names to include in the subject alternative name.
    These names will be used for server name verification. This is useful if
    JupyterHub is being run behind a reverse proxy or services using ssl are on
    different hosts.
    Use with internal_ssl
    Default: []
--JupyterHub.trusted_downstream_ips=<list-item-1>...
    Downstream proxy IP addresses to trust.
    This sets the list of IP addresses that are trusted and skipped when
    processing the `X-Forwarded-For` header. For example, if an external proxy
    is used for TLS termination, its IP address should be added to this list to
    ensure the correct client IP addresses are recorded in the logs instead of
    the proxy server's IP address.
    Default: []
--JupyterHub.upgrade_db=<Bool>
    Upgrade the database automatically on start.
    Only safe if database is regularly backed up. Only SQLite databases will be
    backed up to a local file automatically.
    Default: False
--JupyterHub.user_redirect_hook=<Callable>
    Callable to affect behavior of /user-redirect/
    Receives 4 parameters: 1. path - URL path that was provided after /user-
    redirect/ 2. request - A Tornado HTTPServerRequest representing the current
    request. 3. user - The currently authenticated user. 4. base_url - The
    base_url of the current hub, for relative redirects
    It should return the new URL to redirect to, or None to preserve current
    behavior.
    Default: None

Spawner(LoggingConfigurable) options
------------------------------------
--Spawner.args=<list-item-1>...
    Extra arguments to be passed to the single-user server.
    Some spawners allow shell-style expansion here, allowing you to use
    environment variables here. Most, including the default, do not. Consult the
    documentation for your spawner to verify!
    Default: []
--Spawner.auth_state_hook=<Any>
    An optional hook function that you can implement to pass `auth_state` to the
    spawner after it has been initialized but before it starts. The `auth_state`
    dictionary may be set by the `.authenticate()` method of the authenticator.
    This hook enables you to pass some or all of that information to your
    spawner.
    Example::
        def userdata_hook(spawner, auth_state):
            spawner.userdata = auth_state["userdata"]
        c.Spawner.auth_state_hook = userdata_hook
    Default: None
--Spawner.cmd=<command-item-1>...
    The command used for starting the single-user server.
    Provide either a string or a list containing the path to the startup script
    command. Extra arguments, other than this path, should be provided via
    `args`.
    This is usually set if you want to start the single-user server in a
    different python environment (with virtualenv/conda) than JupyterHub itself.
    Some spawners allow shell-style expansion here, allowing you to use
    environment variables. Most, including the default, do not. Consult the
    documentation for your spawner to verify!
    Default: ['jupyterhub-singleuser']
--Spawner.consecutive_failure_limit=<Int>
    Maximum number of consecutive failures to allow before shutting down
    JupyterHub.
    This helps JupyterHub recover from a certain class of problem preventing
    launch in contexts where the Hub is automatically restarted (e.g. systemd,
    docker, kubernetes).
    A limit of 0 means no limit and consecutive failures will not be tracked.
    Default: 0
--Spawner.cpu_guarantee=<Float>
    Minimum number of cpu-cores a single-user notebook server is guaranteed to
    have available.
    If this value is set to 0.5, allows use of 50% of one CPU. If this value is
    set to 2, allows use of up to 2 CPUs.
    **This is a configuration setting. Your spawner must implement support for
    the limit to work.** The default spawner, `LocalProcessSpawner`, does
    **not** implement this support. A custom spawner **must** add support for
    this setting for it to be enforced.
    Default: None
--Spawner.cpu_limit=<Float>
    Maximum number of cpu-cores a single-user notebook server is allowed to use.
    If this value is set to 0.5, allows use of 50% of one CPU. If this value is
    set to 2, allows use of up to 2 CPUs.
    The single-user notebook server will never be scheduled by the kernel to use
    more cpu-cores than this. There is no guarantee that it can access this many
    cpu-cores.
    **This is a configuration setting. Your spawner must implement support for
    the limit to work.** The default spawner, `LocalProcessSpawner`, does
    **not** implement this support. A custom spawner **must** add support for
    this setting for it to be enforced.
    Default: None
--Spawner.debug=<Bool>
    Enable debug-logging of the single-user server
    Default: False
--Spawner.default_url=<Unicode>
    The URL the single-user server should start in.
    `{username}` will be expanded to the user's username
    Example uses:
    - You can set `notebook_dir` to `/` and `default_url` to `/tree/home/{username}` to allow people to
      navigate the whole filesystem from their notebook server, but still start in their home directory.
    - Start with `/notebooks` instead of `/tree` if `default_url` points to a notebook instead of a directory.
    - You can set this to `/lab` to have JupyterLab start by default, rather than Jupyter Notebook.
    Default: ''
--Spawner.disable_user_config=<Bool>
    Disable per-user configuration of single-user servers.
    When starting the user's single-user server, any config file found in the
    user's $HOME directory will be ignored.
    Note: a user could circumvent this if the user modifies their Python
    environment, such as when they have their own conda environments /
    virtualenvs / containers.
    Default: False
--Spawner.env_keep=<list-item-1>...
    List of environment variables for the single-user server to inherit from the
    JupyterHub process.
    This list is used to ensure that sensitive information in the JupyterHub
    process's environment (such as `CONFIGPROXY_AUTH_TOKEN`) is not passed to
    the single-user server's process.
    Default: ['PATH', 'PYTHONPATH', 'CONDA_ROOT', 'CONDA_DEFAULT_ENV', 'VI...
--Spawner.environment=<key-1>=<value-1>...
    Extra environment variables to set for the single-user server's process.
    Environment variables that end up in the single-user server's process come from 3 sources:
      - This `environment` configurable
      - The JupyterHub process' environment variables that are listed in `env_keep`
      - Variables to establish contact between the single-user notebook and the hub (such as JUPYTERHUB_API_TOKEN)
    The `environment` configurable should be set by JupyterHub administrators to
    add installation specific environment variables. It is a dict where the key
    is the name of the environment variable, and the value can be a string or a
    callable. If it is a callable, it will be called with one parameter (the
    spawner instance), and should return a string fairly quickly (no blocking
    operations please!).
    Note that the spawner class' interface is not guaranteed to be exactly same
    across upgrades, so if you are using the callable take care to verify it
    continues to work after upgrades!
    .. versionchanged:: 1.2
        environment from this configuration has highest priority,
        allowing override of 'default' env variables,
        such as JUPYTERHUB_API_URL.
    Default: {}
--Spawner.http_timeout=<Int>
    Timeout (in seconds) before giving up on a spawned HTTP server
    Once a server has successfully been spawned, this is the amount of time we
    wait before assuming that the server is unable to accept connections.
    Default: 30
--Spawner.ip=<Unicode>
    The IP address (or hostname) the single-user server should listen on.
    The JupyterHub proxy implementation should be able to send packets to this
    interface.
    Default: ''
--Spawner.mem_guarantee=<ByteSpecification>
    Minimum number of bytes a single-user notebook server is guaranteed to have
    available.
    Allows the following suffixes:
      - K -> Kilobytes
      - M -> Megabytes
      - G -> Gigabytes
      - T -> Terabytes
    **This is a configuration setting. Your spawner must implement support for
    the limit to work.** The default spawner, `LocalProcessSpawner`, does
    **not** implement this support. A custom spawner **must** add support for
    this setting for it to be enforced.
    Default: None
--Spawner.mem_limit=<ByteSpecification>
    Maximum number of bytes a single-user notebook server is allowed to use.
    Allows the following suffixes:
      - K -> Kilobytes
      - M -> Megabytes
      - G -> Gigabytes
      - T -> Terabytes
    If the single user server tries to allocate more memory than this, it will
    fail. There is no guarantee that the single-user notebook server will be
    able to allocate this much memory - only that it can not allocate more than
    this.
    **This is a configuration setting. Your spawner must implement support for
    the limit to work.** The default spawner, `LocalProcessSpawner`, does
    **not** implement this support. A custom spawner **must** add support for
    this setting for it to be enforced.
    Default: None
--Spawner.notebook_dir=<Unicode>
    Path to the notebook directory for the single-user server.
    The user sees a file listing of this directory when the notebook interface
    is started. The current interface does not easily allow browsing beyond the
    subdirectories in this directory's tree.
    `~` will be expanded to the home directory of the user, and {username} will
    be replaced with the name of the user.
    Note that this does *not* prevent users from accessing files outside of this
    path! They can do so with many other means.
    Default: ''
--Spawner.options_form=<Union>
    An HTML form for options a user can specify on launching their server.
    The surrounding `<form>` element and the submit button are already provided.
    For example:
    .. code:: html
        Set your key:
        <input name="key" val="default_key"></input>
        <br>
        Choose a letter:
        <select name="letter" multiple="true">
          <option value="A">The letter A</option>
          <option value="B">The letter B</option>
        </select>
    The data from this form submission will be passed on to your spawner in
    `self.user_options`
    Instead of a form snippet string, this could also be a callable that takes
    as one parameter the current spawner instance and returns a string. The
    callable will be called asynchronously if it returns a future, rather than a
    str. Note that the interface of the spawner class is not deemed stable
    across versions, so using this functionality might cause your JupyterHub
    upgrades to break.
    Default: traitlets.Undefined
--Spawner.poll_interval=<Int>
    Interval (in seconds) on which to poll the spawner for single-user server's
    status.
    At every poll interval, each spawner's `.poll` method is called, which
    checks if the single-user server is still running. If it isn't running, then
    JupyterHub modifies its own state accordingly and removes appropriate routes
    from the configurable proxy.
    Default: 30
--Spawner.port=<Int>
    The port for single-user servers to listen on.
    Defaults to `0`, which uses a randomly allocated port number each time.
    If set to a non-zero value, all Spawners will use the same port, which only
    makes sense if each server is on a different address, e.g. in containers.
    New in version 0.7.
    Default: 0
--Spawner.post_stop_hook=<Any>
    An optional hook function that you can implement to do work after the
    spawner stops.
    This can be set independent of any concrete spawner implementation.
    Default: None
--Spawner.pre_spawn_hook=<Any>
    An optional hook function that you can implement to do some bootstrapping
    work before the spawner starts. For example, create a directory for your
    user or load initial content.
    This can be set independent of any concrete spawner implementation.
    This maybe a coroutine.
    Example::
        from subprocess import check_call
        def my_hook(spawner):
            username = spawner.user.name
            check_call(['./examples/bootstrap-script/bootstrap.sh', username])
        c.Spawner.pre_spawn_hook = my_hook
    Default: None
--Spawner.ssl_alt_names=<list-item-1>...
    List of SSL alt names
    May be set in config if all spawners should have the same value(s), or set
    at runtime by Spawner that know their names.
    Default: []
--Spawner.ssl_alt_names_include_local=<Bool>
    Whether to include DNS:localhost, IP:127.0.0.1 in alt names
    Default: True
--Spawner.start_timeout=<Int>
    Timeout (in seconds) before giving up on starting of single-user server.
    This is the timeout for start to return, not the timeout for the server to
    respond. Callers of spawner.start will assume that startup has failed if it
    takes longer than this. start should return when the server process is
    started and its location is known.
    Default: 60

Authenticator(LoggingConfigurable) options
------------------------------------------
--Authenticator.admin_users=<set-item-1>...
    Set of users that will have admin rights on this JupyterHub.
    Admin users have extra privileges:
     - Use the admin panel to see list of users logged in
     - Add / remove users in some authenticators
     - Restart / halt the hub
     - Start / stop users' single-user servers
     - Can access each individual users' single-user server (if configured)
    Admin access should be treated the same way root access is.
    Defaults to an empty set, in which case no user has admin access.
    Default: set()
--Authenticator.allowed_users=<set-item-1>...
    Set of usernames that are allowed to log in.
    Use this with supported authenticators to restrict which users can log in.
    This is an additional list that further restricts users, beyond whatever
    restrictions the authenticator has in place.
    If empty, does not perform any additional restriction.
    .. versionchanged:: 1.2
        `Authenticator.whitelist` renamed to `allowed_users`
    Default: set()
--Authenticator.auth_refresh_age=<Int>
    The max age (in seconds) of authentication info before forcing a refresh of
    user auth info.
    Refreshing auth info allows, e.g. requesting/re-validating auth tokens.
    See :meth:`.refresh_user` for what happens when user auth info is refreshed
    (nothing by default).
    Default: 300
--Authenticator.auto_login=<Bool>
    Automatically begin the login process
    rather than starting with a "Login with..." link at `/hub/login`
    To work, `.login_url()` must give a URL other than the default `/hub/login`,
    such as an oauth handler or another automatic login handler, registered with
    `.get_handlers()`.
    .. versionadded:: 0.8
    Default: False
--Authenticator.blocked_users=<set-item-1>...
    Set of usernames that are not allowed to log in.
    Use this with supported authenticators to restrict which users can not log
    in. This is an additional block list that further restricts users, beyond
    whatever restrictions the authenticator has in place.
    If empty, does not perform any additional restriction.
    .. versionadded: 0.9
    .. versionchanged:: 1.2
        `Authenticator.blacklist` renamed to `blocked_users`
    Default: set()
--Authenticator.delete_invalid_users=<Bool>
    Delete any users from the database that do not pass validation
    When JupyterHub starts, `.add_user` will be called on each user in the
    database to verify that all users are still valid.
    If `delete_invalid_users` is True, any users that do not pass validation
    will be deleted from the database. Use this if users might be deleted from
    an external system, such as local user accounts.
    If False (default), invalid users remain in the Hub's database and a warning
    will be issued. This is the default to avoid data loss due to config
    changes.
    Default: False
--Authenticator.enable_auth_state=<Bool>
    Enable persisting auth_state (if available).
    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.
    Additionally, the JUPYTERHUB_CRYPT_KEY environment variable must contain one
    (or more, separated by ;) 32B encryption keys. These can be either base64 or
    hex-encoded.
    If encryption is unavailable, auth_state cannot be persisted.
    New in JupyterHub 0.8
    Default: False
--Authenticator.post_auth_hook=<Any>
    An optional hook function that you can implement to do some bootstrapping
    work during authentication. For example, loading user account details from
    an external system.
    This function is called after the user has passed all authentication checks
    and is ready to successfully authenticate. This function must return the
    authentication dict reguardless of changes to it.
    This maybe a coroutine.
    .. versionadded: 1.0
    Example::
        import os, pwd
        def my_hook(authenticator, handler, authentication):
            user_data = pwd.getpwnam(authentication['name'])
            spawn_data = {
                'pw_data': user_data
                'gid_list': os.getgrouplist(authentication['name'], user_data.pw_gid)
            }
            if authentication['auth_state'] is None:
                authentication['auth_state'] = {}
            authentication['auth_state']['spawn_data'] = spawn_data
            return authentication
        c.Authenticator.post_auth_hook = my_hook
    Default: None
--Authenticator.refresh_pre_spawn=<Bool>
    Force refresh of auth prior to spawn.
    This forces :meth:`.refresh_user` to be called prior to launching a server,
    to ensure that auth state is up-to-date.
    This can be important when e.g. auth tokens that may have expired are passed
    to the spawner via environment variables from auth_state.
    If refresh_user cannot refresh the user auth data, launch will fail until
    the user logs in again.
    Default: False
--Authenticator.username_map=<key-1>=<value-1>...
    Dictionary mapping authenticator usernames to JupyterHub users.
    Primarily used to normalize OAuth user names to local users.
    Default: {}
--Authenticator.username_pattern=<Unicode>
    Regular expression pattern that all valid usernames must match.
    If a username does not match the pattern specified here, authentication will
    not be attempted.
    If not set, allow any username.
    Default: ''
--Authenticator.whitelist=<set-item-1>...
    Deprecated, use `Authenticator.allowed_users`
    Default: set()

CryptKeeper(SingletonConfigurable) options
------------------------------------------
--CryptKeeper.keys=<list-item-1>...
    Default: []
--CryptKeeper.n_threads=<Int>
    The number of threads to allocate for encryption
    Default: 1

Examples
--------

    generate default config file:
    
        jupyterhub --generate-config -f /etc/jupyterhub/jupyterhub_config.py
    
    spawn the server on 10.0.1.2:443 with https:
    
        jupyterhub --ip 10.0.1.2 --port 443 --ssl-key my_ssl.key --ssl-cert my_ssl.cert