Commit 6af83582 authored by Jim Fulton's avatar Jim Fulton

Bootstrapping topic

parent d6614296
=========
Reference
=========
The Buildout command line
=========================
A Buildout execution is of the form:
.. code-block:: console
buildout [buildout-options] [settings] [subcommand [subcommand-arguments]]
Buildout options
----------------
Buildout subcommands
--------------------
.. _bootstrap-subcommand:
bootstrap
_________
Install a local ``bootstrap`` script. The ``bootstrap`` subcommand
doesn't take any arguments.
See :doc:`Bootstrapping <topics/bootstrapping>` for information on why
you might want to do this.
.. _init-subcommand:
init [requirements]
____________________
Generate a Buildout configuration file and bootstrap the resulting buildout.
If requirements are given, the generated configuration will have a
``py`` part that uses the ``zc.recipe.egg`` recipe to install the
requirements and generate an interpreter script that can import them.
It then runs the resulting buildout.
See :ref:`Bootstrapping <init-generates-buildout.cfg>` for examples.
=============
Bootstrapping
=============
Bootstrapping a buildout gives its own ``buildout`` script,
independent of its Python environment. There are 2 reasons you might use this:
Enable automatic Buildout upgrade (or downgrade).
If the ``buildout`` script is local to the buildout, then Buildout
will check for newest versions of Buildout and its dependencies
that are consistent with any version pins and install any that are
different, in which case, it restarts to use the new versions.
Doing automatic upgrades allows buildouts to be more independent of
their environments and more repeatable.
Using a local ``buildout`` script may be necessary for a project that
pins the version of Buildout itself and the pinned version is
different from the version in the Python environment.
Avoid modifying the python environment.
From a philosophical point of view, Buildout has tried to be
isolated from its environment, and requiring the Python environment
to be modified, by installing Buildout, was inconsistent.
Before `virtualenv <https://virtualenv.pypa.io/en/stable/>`_
existed, it might not have been possible to modify the environment
without building Python from source.
Unfortunately, doing this this requires :ref:`using a bootstrap script
<using-a-bootstrap-script>`.
Local bootstrapping using the ``buildout`` subcommand
=====================================================
You can use the :ref:`bootstrap subcommand <bootstrap-subcommand>` of a
``buildout`` script installed in your Python environment to boostrap
the buildout in the current directory:
.. code-block:: console
buildout bootstrap
If you have any other buildouts that have local ``buildout`` scripts, you
can use their ``buildout`` scripts:
.. code-block:: console
/path/to/some/buildout/bin/buildout bootstrap
In this case, the buildout being bootstrapped will have the same
Python environment as the buildout that was used to bootstrap it.
.. _using-a-bootstrap-script:
Using a bootstrapping script
============================
If you download::
https://bootstrap.pypa.io/bootstrap-buildout.py
And then run it:
.. code-block:: console
python bootstrap-buildout.py
It will download the software needed to run Buildout and install it in
the current directory.
This has been the traditional approach to bootstrapping Buildout.
It was the best approach for a long time because the ``pip`` and
``easy_install`` commands usually weren't available. In the early
days, if ``easy_install`` was installed, it was likely to have an
incompatible version of setuptools, because Buildout and setuptools
were evolving rapidly, sometimes in lock step.
This approach fails from time to time, due to changes in setuptools or
`the package index <https://pypi.python.org/pypi>`_ and has been a
source of breakage when automated systems depended on it.
It's also possible that this approach will stop being supported.
Buildout's bootstrapping script relies on setuptools' bootstrap
script, which was used to bootstrap ``easy_install``. Now that pip is
ubiquitous, there's no reason to bootstrap ``easy_install`` and
setuptools' bootstrapping script exists solely to support Buildout.
At some point, that may become too much of a maintenance burden, and
there may not be Buildout volunteers motivated to create a new
bootstrapping solution.
.. _init-generates-buildout.cfg:
bootstrapping requires a ``buildout.cfg``, ``init`` creates one
==================================================================
Normally, when bootstrapping, the local directory must have a
``buildout.cfg`` file.
If you don't have one, you can use the :ref:`init subcommand
<init-subcommand>` instead:
.. code-block:: console
buildout init
This can be used with the bootstrapping script as well:
.. code-block:: console
python bootstrap-buildout.py init
This creates an empty Buildout configuration:
.. code-block:: ini
[buildout]
parts =
If you know you're going to use some packages, you can supply
requirements on the command line after ``init``:
.. code-block:: console
buildout init ZODB six
In which case it will generate and run a buildout that uses them. The
command above would generate a buildout configuration file:
.. code-block:: ini
[buildout]
parts = py
[py]
recipe = zc.recipe.egg
interpreter = py
eggs =
ZODB
six
This can provide an easy way to experiment with a package without
adding it to your Python environment or creating a virtualenv.
......@@ -6,6 +6,7 @@ Buildout Topics
:maxdepth: 2
history
bootstrapping
.. todo:
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