text: # Configuration file for jupyterhub.
  
  #------------------------------------------------------------------------------
  # Application(SingletonConfigurable) configuration
  #------------------------------------------------------------------------------
  
  ## This is an application.
  
  ## The date format used by logging formatters for %(asctime)s
  #c.Application.log_datefmt = '%Y-%m-%d %H:%M:%S'
  
  ## The Logging format template
  #c.Application.log_format = '[%(name)s]%(highlevel)s %(message)s'
  
  ## Set the log level by value or name.
  #c.Application.log_level = 30
  
  #------------------------------------------------------------------------------
  # 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.
  #c.JupyterHub.active_server_limit = 0
  c.JupyterHub.active_server_limit = 50
  
  ## Duration (in seconds) to determine the number of active users.
  #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.
  #c.JupyterHub.activity_resolution = 30
  
  ## Grant admin users permission to access single-user servers.
  #  
  #  Users should be properly informed if this is enabled.
  #c.JupyterHub.admin_access = False
  c.JupyterHub.admin_access = True
  
  ## DEPRECATED since version 0.7.2, use Authenticator.admin_users instead.
  #c.JupyterHub.admin_users = set()
  
  ## Allow named single-user servers per user
  #c.JupyterHub.allow_named_servers = False
  c.JupyterHub.allow_named_servers = True
  
  ## Answer yes to any questions (e.g. confirm overwrite)
  #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.
  #c.JupyterHub.api_tokens = {}
  
  ## Authentication for prometheus metrics
  #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
  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
  #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
  #c.JupyterHub.bind_url = 'http://:8000'
  #c.JupyterHub.bind_url = 'http://127.0.0.1:8000'
  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.
  #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.
  #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.
  #c.JupyterHub.concurrent_spawn_limit = 100
  c.JupyterHub.concurrent_spawn_limit = 10
  
  ## The config file to load
  #c.JupyterHub.config_file = 'jupyterhub_config.py'
  
  ## DEPRECATED: does nothing
  #c.JupyterHub.confirm_no_ssl = False
  
  ## Number of days for a login cookie to be valid. Default is two weeks.
  #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).
  #c.JupyterHub.cookie_secret = b''
  
  ## File in which to store the cookie secret.
  #c.JupyterHub.cookie_secret_file = 'jupyterhub_cookie_secret'
  
  ## The location of jupyterhub data files (e.g. /usr/local/share/jupyterhub)
  #c.JupyterHub.data_files_path = '/usr/local/share/jupyterhub'
  
  ## Include any kwargs to pass to the database connection. See
  #  sqlalchemy.create_engine for details.
  #c.JupyterHub.db_kwargs = {}
  
  ## url for the database. e.g. `sqlite:///jupyterhub.sqlite`
  #c.JupyterHub.db_url = 'sqlite:///jupyterhub.sqlite'
  
  ## log all database transactions. This has A LOT of output
  #c.JupyterHub.debug_db = False
  
  ## DEPRECATED since version 0.8: Use ConfigurableHTTPProxy.debug
  #c.JupyterHub.debug_proxy = False
  
  ## If named servers are enabled, default name of server to spawn or open, e.g. by
  #  user-redirect.
  #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.
  #c.JupyterHub.default_url = ''
  #c.JupyterHub.default_url = '/lab'
  
  ## 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
  #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`.
  #c.JupyterHub.extra_handlers = []
  
  ## DEPRECATED: use output redirection instead, e.g.
  #  
  #  jupyterhub &>> /var/log/jupyterhub.log
  #c.JupyterHub.extra_log_file = ''
  
  ## Extra log handlers to set on JupyterHub logger
  #c.JupyterHub.extra_log_handlers = []
  
  ## Generate certs used for internal ssl
  #c.JupyterHub.generate_certs = False
  
  ## Generate default config file
  #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
  #c.JupyterHub.hub_bind_url = ''
  c.JupyterHub.hub_bind_url = 'http://127.0.0.1:8081'
  
  ## 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
  #c.JupyterHub.hub_connect_ip = ''
  c.JupyterHub.hub_connect_ip = '127.0.0.1'
  
  ## DEPRECATED
  #  
  #  Use hub_connect_url
  #  
  #  .. versionadded:: 0.8
  #  
  #  .. deprecated:: 0.9
  #      Use hub_connect_url
  #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
  #c.JupyterHub.hub_connect_url = ''
  #c.JupyterHub.hub_connect_url = 'http://127.0.0.1:8000'
  
  ## 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.
  c.JupyterHub.hub_ip = ''
  
  ## 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.
  #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.
  #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
  #c.JupyterHub.init_spawners_timeout = 10
  
  ## The location to store certificates automatically created by JupyterHub.
  #  
  #  Use with 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.
  #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
  #c.JupyterHub.ip = ''
  
  ## Supply extra arguments that will be passed to Jinja environment.
  #c.JupyterHub.jinja_environment_options = {}
  
  ## Interval (in seconds) at which to update last-activity timestamps.
  #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.
  #c.JupyterHub.load_groups = {'jupyterhub': ['user']}
  
  ## Specify path to a logo image to override the Jupyter logo in the banner.
  #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.
  #c.JupyterHub.named_server_limit_per_user = 0
  
  ## File to write PID Useful for daemonizing JupyterHub.
  #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
  #c.JupyterHub.port = 8000
  
  ## DEPRECATED since version 0.8 : Use ConfigurableHTTPProxy.api_url
  #c.JupyterHub.proxy_api_ip = ''
  
  ## DEPRECATED since version 0.8 : Use ConfigurableHTTPProxy.api_url
  #c.JupyterHub.proxy_api_port = 0
  
  ## DEPRECATED since version 0.8: Use ConfigurableHTTPProxy.auth_token
  #c.JupyterHub.proxy_auth_token = ''
  
  ## Interval (in seconds) at which to check if the proxy is running.
  #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
  #c.JupyterHub.proxy_class = 'jupyterhub.proxy.ConfigurableHTTPProxy'
  
  ## DEPRECATED since version 0.8. Use ConfigurableHTTPProxy.command
  #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
  #c.JupyterHub.recreate_internal_certs = False
  
  ## Redirect user to server (if running), instead of control panel.
  #c.JupyterHub.redirect_to_server = True
  
  ## Purge and reset the database.
  #c.JupyterHub.reset_db = False
  
  ## Interval (in seconds) at which to check connectivity of services with web
  #  endpoints.
  #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.
  #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':
  #          }
  #      ]
  #c.JupyterHub.services = []
  
  ## Shuts down all user servers on logout
  #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
  #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
  #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
  #c.JupyterHub.ssl_key = ''
  
  ## Host to send statsd metrics to. An empty string (the default) disables sending
  #  metrics.
  #c.JupyterHub.statsd_host = ''
  
  ## Port on which to send statsd metrics about the hub
  #c.JupyterHub.statsd_port = 8125
  
  ## Prefix to use for all metrics sent by jupyterhub to statsd
  #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.
  #c.JupyterHub.subdomain_host = ''
  
  ## Paths to search for jinja templates, before using the default templates.
  #c.JupyterHub.template_paths = []
  
  ## Extra variables to be passed into jinja templates
  #c.JupyterHub.template_vars = {}
  
  ## Extra settings overrides to pass to the tornado application.
  #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.
  #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
  #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.
  c.JupyterHub.trusted_downstream_ips = ['127.0.0.1']
  
  ## 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.
  #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.
  #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!
  #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
  #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!
  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.
  #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.
  #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.
  #c.Spawner.cpu_limit = None
  
  ## Enable debug-logging of the single-user server
  #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.
  c.Spawner.default_url = ''
  #c.Spawner.default_url = '/lab'
  
  ## 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.
  #c.Spawner.disable_user_config = False
  
  ## Whitelist of environment variables for the single-user server to inherit from
  #  the JupyterHub process.
  #  
  #  This whitelist 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.
  #c.Spawner.env_keep = ['PATH', 'PYTHONPATH', 'CONDA_ROOT', 'CONDA_DEFAULT_ENV', 'VIRTUAL_ENV', 'LANG', 'LC_ALL']
  
  ## 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 whitelisted 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!
  #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.
  #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.
  #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.
  #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.
  #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.
  c.Spawner.notebook_dir = '/work/{username}/'
  
  ## 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.
  #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.
  #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.
  #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.
  #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
  #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.
  #c.Spawner.ssl_alt_names = []
  
  ## Whether to include DNS:localhost, IP:127.0.0.1 in alt names
  #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.
  #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.
  c.Authenticator.admin_users = set(["user"])
  
  ## 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).
  #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
  #c.Authenticator.auto_login = False
  
  ## Blacklist 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 blacklist that further restricts users, beyond whatever
  #  restrictions the authenticator has in place.
  #  
  #  If empty, does not perform any additional restriction.
  #  
  #  .. versionadded: 0.9
  c.Authenticator.blacklist = set(["root", "jovyan"])
  
  ## 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
  #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
  #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.
  #c.Authenticator.refresh_pre_spawn = False
  
  ## Dictionary mapping authenticator usernames to JupyterHub users.
  #  
  #  Primarily used to normalize OAuth user names to local users.
  #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.
  #c.Authenticator.username_pattern = ''
  
  ## Whitelist of usernames that are allowed to log in.
  #  
  #  Use this with supported authenticators to restrict which users can log in.
  #  This is an additional whitelist that further restricts users, beyond whatever
  #  restrictions the authenticator has in place.
  #  
  #  If empty, does not perform any additional restriction.
  #c.Authenticator.whitelist = set(["user"])
  
  #------------------------------------------------------------------------------
  # CryptKeeper(SingletonConfigurable) configuration
  #------------------------------------------------------------------------------
  
  ## Encapsulate encryption configuration
  #  
  #  Use via the encryption_config singleton below.
  
  ## 
  #c.CryptKeeper.keys = []
  
  ## The number of threads to allocate for encryption
  #c.CryptKeeper.n_threads = 64
  c.LatexConfig.latex_command = 'pdflatex'
  