diff --git a/doc/conf.py b/doc/conf.py
index 0a41b0a..2a303c9 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -9,7 +9,7 @@
 	subprocess.call('doxygen lisp.doxyfile', shell=True)
 
 project = 'Bluejay'
-copyright = '2021, swissChili'
+copyright = '2022, swissChili'
 author = 'swissChili'
 
 extensions = [
diff --git a/doc/index.rst b/doc/index.rst
index 90900ce..6546d15 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -11,6 +11,7 @@
    :hidden:
 
    build
+   jmk
    architecture
    filesystem
    lisp-std
diff --git a/doc/jmk.rst b/doc/jmk.rst
new file mode 100644
index 0000000..224abc8
--- /dev/null
+++ b/doc/jmk.rst
@@ -0,0 +1,80 @@
+JMK 2 Build System
+==================
+
+JMK2 is a rewrite of the JMK build system. I am slowly porting
+Bluejay to JMK2 instead of the legacy M4-based JMK build system.
+
+JMK2 is used to generate makefiles for each project in Bluejay. A
+project is a directory with a ``Jmk2`` file (case sensitive). Each
+project produces a single output based on some sources.
+
+The script ``bin/jmk2`` looks in the source tree for ``Jmk2`` files,
+and process each one into the corresponding Makefile. It accepts
+option definitions with the ``-D`` flag, eg ``./bin/jmk2
+-DSOME_OPTION=123``.
+
+Here is an example Jmk2 file:
+
+.. code-block:: tcl
+
+    init hello # hello is the name of the project
+    srcs hello.c world.c # the source files this project uses
+    type executable # the preset type of project this is
+
+Each line consists of a command (``init``, ``srcs``, ``type``) and its
+arguments. The commands are documented here:
+
+.. function:: init name [target]
+
+    Initializes the project with a given name. The ``name`` is currently
+    unused, but should be set to a descriptive identifier.
+
+    ``target`` is the name of the target that the project
+    generates. By default it is the same as ``name``. For an
+    executable, this could be ``hello`` or ``hello.exe``. For a shared
+    library, ``libhello.so``, etc.
+
+.. function:: preset preset_name
+
+    Applies the preset ``preset_name``. A preset is a function defined
+    in the ``::presets`` namespace which makes some changes to the
+    project state.
+
+    These are the default presets:
+
+    * ``freestanding`` Changes the ``cflags`` to build a freestanding binary (without linking the standard library).
+    * ``optimize`` Changes the ``cflags`` and ``asmflags`` to enable \
+      compile-time optimizations.
+    * ``32`` Tells the compilers to produce a 32 bit build.
+    * ``debug`` Tells the compilers to enable debug information in the \
+      resulting builds (enables DWARF symbols).
+    * ``warn`` Enables useful warnings and ``-Werror``.
+    * ``nasm`` Sets ``nasm`` as the default assembler.
+
+.. function:: presets preset_a [preset_b]...
+
+    Applies all the given presets in order. Identical to calling
+    ``preset`` once for each argument.
+
+.. function:: cflag string
+
+    Adds ``string`` to the ``::cflags`` variable, which will be passed
+    to the C compiler.
+
+.. function:: cflags string_a [string_b]...
+
+    Adds multiple strings to the ``::cflags`` variable, the same as
+    calling ``cflags`` repeatedly.
+
+.. function:: asmflag, asmflags
+
+    Same as ``cflag``, ``cflags`` but for the ``::asmflags`` variable.
+
+.. function:: option name default_value
+
+    If the option ``name`` has not been specified when invoking
+    ``bin/jmk2``, sets the value of the option to
+    ``default_value``. Options can be read with
+    ``::options(option_name)``.
+
+TODO: finish!