diff --git a/docs/README.rst b/docs/README.rst
index d2f45a4..5f65482 100644
--- a/docs/README.rst
+++ b/docs/README.rst
@@ -31,6 +31,12 @@ which contains the currently released version. This formula is versioned accordi
 
 See `Formula Versioning Section <https://docs.saltstack.com/en/latest/topics/development/conventions/formulas.html#versioning>`_ for more details.
 
+If you need (non-default) configuration, please refer to:
+
+- `how to configure the formula with map.jinja <map.jinja.rst>`_
+- the ``pillar.example`` file
+
+
 Contributing to this repo
 -------------------------
 
diff --git a/docs/map.jinja.rst b/docs/map.jinja.rst
new file mode 100644
index 0000000..dab217b
--- /dev/null
+++ b/docs/map.jinja.rst
@@ -0,0 +1,447 @@
+.. _map.jinja:
+
+``map.jinja``: gather formula configuration values
+==================================================
+
+The `documentation`_ explains the use of a ``map.jinja`` to gather parameters values for a formula.
+
+As `pillars`_ are rendered on the Salt master for every minion, this increases the load on the master as the pillar values and the number of minions grows.
+
+As a good practice, you should:
+
+- store non-secret data in YAML files distributed by the `fileserver`_
+- store secret data in:
+
+  - `pillars`_ (and look for the use of something like `pillar.vault`_)
+  - `SDB`_ (and look for the use of something like `sdb.vault`_)
+
+Current best practice is to let ``map.jinja`` handle parameters from all sources, to minimise the use of pillars, grains or configuration from ``sls`` files and templates directly.
+
+
+.. contents:: **Table of Contents**
+
+
+For formula users
+-----------------
+
+
+Quick start: configure per role and per DNS domain name values
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+We will see a quick setup to configure the ``TEMPLATE`` formula for different DNS domain name and several roles.
+
+For this example, I'll define 2 kinds of `fileserver`_ sources:
+
+1. formulas git repositories with hard-coded version reference to avoid breaking my setup randomly at upstream update. they are the last sources where files are looked up
+2. parameters of the formulas in the file backend `roots`_
+
+
+Configure the fileserver backends
+`````````````````````````````````
+
+I configure the `fileserver`_ backends to serve:
+
+1. files from `roots`_ first
+2. `gitfs`_ repositories last
+
+Create the file ``/etc/salt/master.d/fileserver.conf`` and restart the ``master``:
+
+.. code-block:: yaml
+
+    ---
+    ##
+    ## file server
+    ##
+    fileserver_backend:
+      # parameters values and override
+      - roots
+      # formulas
+      - gitfs
+
+    # The files in this directory will take precedence over git repositories
+    file_roots:
+      base:
+        - /srv/salt
+
+    # List of formulas I'm using
+    gitfs_remotes:
+      - https://github.com/saltstack-formulas/template-formula.git:
+        - base: v4.1.1
+      - https://github.com/saltstack-formulas/openssh-formula.git:
+        - base: v2.0.1
+    ...
+
+
+Create per DNS configuration for ``TEMPLATE`` formula
+`````````````````````````````````````````````````````
+
+Now, we can provides the per DNS domain name configuration files for the ``TEMPLATE`` formulas under ``/srv/salt/TEMPLATE/parameters/``.
+
+We create the directory for ``dns:domain`` grain and we add a symlink for the ``domain`` grain which is extracted from the minion ``id``:
+
+.. code-block:: console
+
+    mkdir -p /srv/salt/TEMPLATE/parameters/dns:domain/
+    ln -s dns:domain /srv/salt/TEMPLATE/parameters/domain
+
+We create a configuration for the DNS domain ``example.net`` in ``/srv/salt/TEMPLATE/parameters/dns:domain/example.net.yaml``:
+
+.. code-block:: yaml
+
+    ---
+    values:
+      config: /etc/template-formula-example-net.conf
+    ...
+
+We create another configuration for the DNS domain ``example.com`` in ``/srv/salt/TEMPLATE/parameters/dns:domain/example.com.yaml``:
+
+.. code-block:: yaml
+
+    ---
+    values:
+      config: /etc/template-formula-{{ grains['os_family'] }}.conf
+    ...
+
+
+Create per role configuration for ``TEMPLATE`` formula
+``````````````````````````````````````````````````````
+
+Now, we can provides the per role configuration files for the ``TEMPLATE`` formulas under ``/srv/salt/TEMPLATE/parameters/``.
+
+We create the directory for roles:
+
+.. code-block:: console
+
+    mkdir -p /srv/salt/TEMPLATE/parameters/roles
+
+We will define 2 roles:
+
+- ``TEMPLATE/server``
+- ``TEMPLATE/client``
+
+We create a configuration for the role ``TEMPLATE/server`` in ``/srv/salt/TEMPLATE/parameters/roles/TEMPLATE/server.yaml``:
+
+.. code-block:: yaml
+
+    ---
+    values:
+      config: /etc/template-formula-server.conf
+    ...
+
+We create another configuration for the role ``TEMPLATE/client`` in ``/srv/salt/TEMPLATE/parameters/roles/TEMPLATE/client.yaml``:
+
+.. code-block:: yaml
+
+    ---
+    values:
+      config: /etc/template-formula-client.conf
+    ...
+
+
+Enable roles and the ``dns:domain`` and ``domain`` grains for ``map.jinja``
+```````````````````````````````````````````````````````````````````````````
+
+We need to redefine the sources for ``map.jinja`` to load values from our new configuration files, we provide a global configuration for all our minions.
+
+We create the global parameters file ``/srv/salt/parameters/map_jinja.yaml``:
+
+.. code-block:: yaml
+
+    ---
+    values:
+      sources:
+        # default values
+        - "Y:G@osarch"
+        - "Y:G@os_family"
+        - "Y:G@os"
+        - "Y:G@osfinger"
+        - "C@{{ tplroot ~ ':lookup' }}"
+        - "C@{{ tplroot }}"
+
+        # Roles activate/deactivate things
+        # then thing are configured depending on environment
+        # So roles comes before `dns:domain`, `domain` and `id`
+        - "Y:C@roles"
+
+        # DNS domain configured (DHCP or resolv.conf)
+        - "Y:G@dns:domain"
+
+        # Based on minion ID
+        - "Y:G@domain"
+
+        # default values
+        - "Y:G@id"
+    ...
+
+The syntax is explained later at `Sources of configuration values`_.
+
+
+Bind roles to minions
+`````````````````````
+
+We associate roles `grains`_ to minion using `grains.append`_.
+
+For the servers:
+
+.. code-block:: console
+
+    salt 'server-*' grains.append roles TEMPLATE/server
+
+For the clients:
+
+.. code-block:: console
+
+    salt 'client-*' grains.append roles TEMPLATE/client
+
+.. note::
+
+    Since we used ``Y:C@roles``, ``map.jinja`` will do a ``salt['config.get']('roles')`` to retrieve the roles so you could use any other method to bind roles to minions (`pillars`_ or `SDB`_) but `grains`_ seems to be the prefered method.
+
+
+Format of configuration YAML files
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+When you write a new YAML file, note that it must conform to the following layout:
+
+- a mandatory ``values`` key to store the configuration values
+- two optional keys to configure the use of `salt.slsutil.merge`_
+
+  - an optional ``strategy`` key to configure the merging strategy, for example ``strategy: 'recurse'``, the default is ``smart``
+  - an optional ``merge_lists`` key to configure if lists should be merged or overridden for the ``recurse`` and ``overwrite`` strategy, for example ``merge_lists: 'true'``
+
+Here is a valid example:
+
+.. code-block:: yaml
+
+    ---
+    strategy: 'recurse'
+    merge_lists: 'false'
+    values:
+      pkg:
+        name: 'some-package'
+      config: '/path/to/a/configuration/file'
+    ...
+
+You can use `Jinja`_ as with any SLS files:
+
+.. code-block:: yaml
+
+    ---
+    strategy: 'overwrite'
+    merge_lists: 'true'
+    values:
+      output_dir: /tmp/{{ grains['id'] }}
+    ...
+
+
+Sources of configuration values
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+
+Configuring ``map.jinja`` sources
+`````````````````````````````````
+
+The ``map.jinja`` file uses several sources where to lookup parameter values. The list of sources can be modified by two files:
+
+1. a global ``salt://parameters/map_jinja.yaml``
+2. a per formula ``salt://{{ tplroot }}/parameters/map_jinja.yaml``, it overrides the global configuration
+
+Each source definition has the form ``<TYPE>:<OPTION>@<KEY>`` where ``<TYPE>`` can be one of:
+
+- ``Y`` to load values from YAML files from the `fileserver`_, this is the default when no type is defined
+- ``C`` to lookup values with `salt['config.get']`_
+- ``G`` to lookup values with `salt['grains.get']`_
+- ``I`` to lookup values with `salt['pillar.get']`_
+
+The YAML type option can define the query method to lookup the key value to build the file name:
+
+- ``C`` to query with `salt['config.get']`_, this is the default when no query method is defined
+- ``G`` to query with `salt['grains.get']`_
+- ``I`` to query with `salt['pillar.get']`_
+
+The ``C``, ``G`` or ``I`` types can define the ``SUB`` option to store values in the sub key ``mapdata.<KEY>`` instead of directly in ``mapdata``.
+
+Finally, the ``<KEY>`` describes what to lookup to either build the YAML filename or gather values using one of the query methods.
+
+.. note::
+
+    For the YAML type, if the ``<KEY>`` can't be looked up, then it's used a literal string path to a YAML file, for example: ``any/path/can/be/used/here.yaml`` will result in the loading of ``salt://{{ tplroot }}/parameters/any/path/can/be/used/here.yaml`` if it exists.
+
+The built-in ``map_jinja:sources`` is:
+
+.. code-block:: yaml
+
+    - "Y:G@osarch"
+    - "Y:G@os_family"
+    - "Y:G@os"
+    - "Y:G@osfinger"
+    - "C@{{ tplroot ~ ':lookup' }}"
+    - "C@{{ tplroot }}"
+    - "Y:G@id"
+
+This is strictly equivalent to the following ``map_jinja.yaml`` using `Jinja`_:
+
+.. code-block:: sls
+
+    values:
+      sources:
+        - "parameters/osarch/{{ salt['grains.get']('osarch') }}.yaml"
+        - "parameters/os_family/{{ salt['grains.get']('os_family') }}.yaml"
+        - "parameters/os/{{ salt['grains.get']('os') }}.yaml"
+        - "parameters/osfinger/{{ salt['grains.get']('osfinger') }}.yaml"
+        - "C@{{ tplroot ~ ':lookup' }}"
+        - "C@{{ tplroot }}"
+        - "parameters/id/{{ salt['grains.get']('id') }}.yaml"
+
+
+Loading values from the configuration sources
+`````````````````````````````````````````````
+
+For each configuration source defined in ``map_jinja:sources``, ``map.jinja`` will:
+
+#. load values depending on the source type:
+
+   - for YAML file sources
+
+     - if the ``<KEY>`` can be looked up, load values from the YAML file named ``salt://{{ tplroot }}/paramaters/<KEY>/{{ salt['<QUERY_METHOD>']('<KEY>') }}.yaml`` if it exists
+     - otherwise, load the YAML file named ``salt://{{ tplroot }}/parameters/<KEY>.yaml`` if it exists
+
+   - for ``C``, ``G`` or ``I`` source type, lookup the value of ``salt['<QUERY_METHOD>']('<KEY>')``
+
+#. merge the loaded values with the previous ones using `salt.slsutil.merge`_
+
+There will be no error if a YAML file does not exists, they are all optional.
+
+
+Configuration values from ``salt['config.get']``
+````````````````````````````````````````````````
+
+For sources with of type ``C`` declared in ``map_jinja:sources``, you can configure the ``merge`` option of `salt['config.get']`_ by defining per formula ``strategy`` configuration key (retrieved with ``salt['config.get'](tplroot ~ ':strategy')`` with one of the following values:
+
+- ``recurse`` merge recursively dictionaries. Non dictionary values replace already defined values
+- ``overwrite`` new value completely replace old ones
+
+By default, no merging is done, the first value found is returned.
+
+
+Global view of the order of preferences
+```````````````````````````````````````
+
+To summarize, here is a complete example of the load order of formula configuration values for an ``AMD64`` ``Ubuntu 18.04`` minion named ``minion1.example.net`` for the ``libvirt`` formula:
+
+#. ``parameters/defaults.yaml``
+#. ``parameters/osarch/amd64.yaml``
+#. ``parameters/os_family/Debian.yaml``
+#. ``parameters/os/Ubuntu.yaml``
+#. ``parameters/osfinger/Ubuntu-18.04.yaml``
+#. ``salt['config.get']('libvirt:lookup')``
+#. ``salt['config.get']('libvirt')``
+#. ``parameters/id/minion1.example.net``
+
+Remember that the order is important, for example, the value of ``key1:subkey1`` loaded from ``parameters/os_family/Debian.yaml`` is overridden by a value loaded from ``parameters/id/minion1.example.net``.
+
+
+For formula authors and contributors
+------------------------------------
+
+Dependencies
+^^^^^^^^^^^^
+
+``map.jinja`` requires:
+
+- salt minion 2018.3.3 minimum to use the `traverse`_ jinja filter
+- to be located at the root of the formula named directory (e.g. ``libvirt-formula/libvirt/map.jinja``)
+- the ``libsaltcli.jinja`` library, stored in the same directory, to disable the ``merge`` option of `salt['config.get']`_ over `salt-ssh`_
+
+
+Use formula configuration values in ``sls``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``map.jinja`` exports a unique ``mapdata`` variable which could be renamed during import.
+
+Here is the best way to use it in an ``sls`` file:
+
+.. code-block:: sls
+
+    {#- Get the `tplroot` from `tpldir` #}
+    {%- set tplroot = tpldir.split("/")[0] %}
+    {%- from tplroot ~ "/map.jinja" import mapdata as TEMPLATE with context %}
+
+    test-does-nothing-but-display-TEMPLATE-as-json:
+      test.nop:
+        - name: {{ TEMPLATE | json }}
+
+
+Use formula configuration values in templates
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+When you need to process salt templates, you should avoid calling `salt['config.get']`_ (or `salt['pillar.get']`_ and `salt['grains.get']`_) directly from the template. All the needed values should be available within the ``mapdata`` variable exported by ``map.jinja``.
+
+Here is an example based on `template-formula/TEMPLATE/config/file.sls`_:
+
+.. code-block:: sls
+
+    # -*- coding: utf-8 -*-
+    # vim: ft=sls
+
+    {#- Get the `tplroot` from `tpldir` #}
+    {%- set tplroot = tpldir.split('/')[0] %}
+    {%- set sls_package_install = tplroot ~ '.package.install' %}
+    {%- from tplroot ~ "/map.jinja" import mapdata as TEMPLATE with context %}
+    {%- from tplroot ~ "/libtofs.jinja" import files_switch with context %}
+
+    include:
+      - {{ sls_package_install }}
+
+    TEMPLATE-config-file-file-managed:
+      file.managed:
+        - name: {{ TEMPLATE.config }}
+        - source: {{ files_switch(['example.tmpl'],
+                                  lookup='TEMPLATE-config-file-file-managed'
+                     )
+                  }}
+        - mode: 644
+        - user: root
+        - group: {{ TEMPLATE.rootgroup }}
+        - makedirs: True
+        - template: jinja
+        - require:
+          - sls: {{ sls_package_install }}
+        - context:
+            TEMPLATE: {{ TEMPLATE | json }}
+
+This ``sls`` file expose a ``TEMPLATE`` context variable to the jinja template which could be used like this:
+
+.. code-block:: jinja
+
+    ########################################################################
+    # File managed by Salt at <{{ source }}>.
+    # Your changes will be overwritten.
+    ########################################################################
+
+    This is another example file from SaltStack template-formula.
+
+    # This is here for testing purposes
+    {{ TEMPLATE | json }}
+
+    winner of the merge: {{ TEMPLATE['winner'] }}
+
+
+.. _documentation: https://docs.saltstack.com/en/latest/topics/development/conventions/formulas.html#writing-formulas
+.. _fileserver: https://docs.saltstack.com/en/latest/ref/file_server
+.. _salt['config.get']: https://docs.saltstack.com/en/latest/ref/modules/all/salt.modules.config.html#salt.modules.config.get
+.. _salt['grains.get']: https://docs.saltstack.com/en/latest/ref/modules/all/salt.modules.grains.html#salt.modules.grains.get
+.. _salt['pillar.get']: https://docs.saltstack.com/en/latest/ref/modules/all/salt.modules.pillar.html#salt.modules.pillar.get
+.. _pillar.vault: https://docs.saltstack.com/en/latest/ref/pillar/all/salt.pillar.vault.html
+.. _pillars: https://docs.saltstack.com/en/latest/topics/pillar/
+.. _grains: https://docs.saltstack.com/en/latest/topics/grains/
+.. _grains.append: https://docs.saltstack.com/en/latest/ref/modules/all/salt.modules.grains.html#salt.modules.grains.append
+.. _SDB: https://docs.saltstack.com/en/latest/topics/sdb/index.html
+.. _sdb.vault: https://docs.saltstack.com/en/latest/ref/sdb/all/salt.sdb.vault.html
+.. _Jinja: https://docs.saltstack.com/en/latest/topics/jinja
+.. _roots: https://docs.saltstack.com/en/latest/ref/file_server/all/salt.fileserver.roots.html
+.. _gitfs: https://docs.saltstack.com/en/latest/topics/tutorials/gitfs.html
+.. _salt.slsutil.merge: https://docs.saltstack.com/en/latest/ref/modules/all/salt.modules.slsutil.html
+.. _traverse: https://docs.saltstack.com/en/latest/topics/jinja/index.html#traverse
+.. _salt-ssh: https://docs.saltstack.com/en/latest/topics/ssh/
+.. _template-formula/TEMPLATE/config/file.sls: https://github.com/saltstack-formulas/template-formula/blob/master/TEMPLATE/config/file.sls