.. _topic/tljh-config:

=====================================
Configuring TLJH with ``tljh-config``
=====================================

``tljh-config`` is the commandline program used to make configuration
changes to TLJH.

Running ``tljh-config``
=======================

You can run ``tljh-config`` in two ways:

#. From inside a terminal in JupyterHub while logged in as an admin user.
   This method is recommended.

#. By directly calling ``/opt/tljh/hub/bin/tljh-config`` as root when
   logged in to the server via other means (such as SSH). This is an
   advanced use case, and not covered much in this guide.

.. _tljh-set:


Set / Unset a configuration property
====================================

TLJH's configuration is organized in a nested tree structure. You can
set a particular property with the following command:

.. code-block:: bash

   sudo tljh-config set <property-path> <value>


where:

#. ``<property-path>`` is a dot-separated path to the property you want
   to set.
#. ``<value>`` is the value you want to set the property to.

For example, to set the password for the DummyAuthenticator, you
need to set the ``auth.DummyAuthenticator.password`` property. You would
do so with the following:

.. code-block:: bash

   sudo tljh-config set auth.DummyAuthenticator.password mypassword


This can only set string and numerical properties, not lists.

To unset a configuration property you can use the following command:

.. code-block:: bash

   sudo tljh-config unset <property-path>

Unsetting a configuration property removes the property from the configuration
file. If what you want is only to change the property's value, you should use
``set`` and overwrite it with the desired value.


Some of the existing ``<property-path>`` are listed below by categories:


.. _tljh-set-auth:

Authentication
--------------

    Use ``auth.type`` to determine authenticator to use. All parameters
    in the config under ``auth.{auth.type}`` will be passed straight to the
    authenticators themselves.

.. _tljh-set-user-lists:

User Lists
----------


* ``users.allowed`` takes in usernames to whitelist

* ``users.banned`` takes in usernames to blacklist

* ``users.admin`` takes in usernames to designate as admins

.. _tljh-set-user-limits:

User Server Limits
------------------


* ``limits.memory`` Specifies the maximum memory that can be used by each
  individual user. By default there is no memory limit. The limit can be
  specified as an absolute byte value. You can use
  the suffixes K, M, G or T to mean Kilobyte, Megabyte, Gigabyte or Terabyte
  respectively. Setting it to ``None`` disables memory limits.

  .. code-block:: bash

     sudo tljh-config set limits.memory 4G

  Even if you want individual users to use as much memory as possible,
  it is still good practice to set a memory limit of 80-90% of total
  physical memory. This prevents one user from being able to single
  handedly take down the machine accidentally by OOMing it.

* ``limits.cpu`` A float representing the total CPU-cores each user can use.
  By default there is no CPU limit.
  1 represents one full CPU, 4 represents 4 full CPUs, 0.5 represents
  half of one CPU, etc. This value is ultimately converted to a percentage and
  rounded down to the nearest integer percentage,
  i.e. 1.5 is converted to 150%, 0.125 is converted to 12%, etc.
  Setting it to ``None`` disables CPU limits.

  .. code-block:: bash

     sudo tljh-config set limits.cpu 2

.. _tljh-set-user-env:

User Environment
----------------


    ``user_environment.default_app`` Set default application users are
    launched into. Currently can be set to the following values
    ``jupyterlab`` or ``nteract``

    .. code-block:: bash

       sudo tljh-config set user_environment.default_app jupyterlab

.. _tljh-view-conf:

View current configuration
==========================

To see the current configuration, you can run the following command:

.. code-block:: bash

   sudo tljh-config show

This will print the current configuration of your TLJH. This is very
useful when asking for support!

.. _tljh-reload-hub:


Reloading JupyterHub to apply configuration
===========================================

After modifying the configuration, you need to reload JupyterHub for
it to take effect. You can do so with:

.. code-block:: bash

   sudo tljh-config reload

This should not affect any running users. The JupyterHub will be
restarted and loaded with the new configuration.

.. _tljh-edit-yaml:

Advanced: ``config.yaml``
=========================

``tljh-config`` is a simple program that modifies the contents of the
``config.yaml`` file located at ``/opt/tljh/config/config.yaml``. ``tljh-config``
is the recommended method of editing / viewing configuration since editing
YAML by hand in a terminal text editor is a large source of errors.
