Introduction
============

Consfigurator is a system for declarative configuration management using
Common Lisp.  You can use it to configure hosts as root, deploy services as
unprivileged users, build and deploy containers, and produce disc images.

Consfigurator's design gives you a great deal of flexibility about how to
control the hosts you want to configure.  Input and output streams attached to
an interactive POSIX sh running on the target host (or in the target
container) is sufficient to use much of Consfigurator's functionality.  But if
it is possible to get an implementation of Common Lisp started up on the host,
then Configurator can transparently execute your deployment code over on the
remote side, rather than exchanging information via POSIX sh.  This lets you
use the full power of Common Lisp to deploy your configuration.

Configurator has convenient abstractions for combining these different ways to
execute your configuration on hosts with different ways of connecting to them.
Connections can be arbitrarily nested.  For example, to combine SSHing to a
Debian machine as an unprivileged user, using sudo to become root, and then
starting up a Lisp image to execute your deployment code, you would just
evaluate ``(deploy (:ssh (:sudo :user "root") :debian-sbcl) foo.example.com)``.

Declarative configuration management systems like Consfigurator and Propellor_
share a number of goals with projects like the `GNU Guix System`_ and
`NixOS`_.  However, tools like Consfigurator and Propellor try to layer the
power of declarative and reproducible configuration on top of traditional,
battle-tested unix system administration infrastructure like apt, dpkg, yum,
and distro package archives, rather than seeking to replace any of those.
Let's get as much as we can out of all that existing distro policy-compliant
work!

[some features described in the preceding are not yet implemented, but
Consfigurator's design should permit them to be soon]

.. _Propellor: https://propellor.branchable.com/
.. _GNU Guix System: https://guix.gnu.org/
.. _NixOS: https://nixos.org/

About the name
--------------

``CONS`` is a fundamental operator in Lisp.  Consfigurator is so named because
we hope to enable configuration management workflows which take advantage of
some of the unique properties of the activity of programming in Lisp.

For example, using Lisp's interactivity, it's easy to test a new property
you're working on without having to plumb it into your main deployments, which
might be large and relatively slow to run.  Hit C-c C-c on your ``DEFPROP``
form in Emacs, switch to the repl, and then use ``DEPLOY-THESE`` to run just
that property against localhost or a local container, until it does what it
should.  For this purpose you can use whatever connection type is most
convenient -- perhaps you normally deploy using Consfigurator's support for
starting up remote Lisp images, but you can swap in a simple, lighter-weight
connection type for testing.

We also have a few nice macros defined, though nothing too clever yet.

Quick start / introduction
==========================

1. ``apt-get install sbcl cl-ppcre cl-interpol cl-alexandria``.

2. Install Consfigurator.  One way to do that is to clone this git repository
   into ``~/.local/share/common-lisp/source``.

3. Create a new directory ``consfig`` somewhere where ASDF will pick it up,
   such as ``~/common-lisp/consfig``.

4. Define a Lisp system which represents your configuration.

    ~/common-lisp/consfig/com.example.consfig.asd::

        (asdf:defsystem :com.example.consfig
          :serial t
          :depends-on (#:consfigurator #:cl-interpol)
          :components ((:file "package")
                       (:file "consfig")))

    ~/common-lisp/consfig/package.lisp::

        (in-package :cl-user)

        (defpackage :com.example.consfig
          (:use #:cl #:consfigurator)
          (:local-nicknames (#:etc-default #:consfigurator.property.etc-default)))

5. Define some hosts and deployments.

    ~/common-lisp/consfig/consfig.lisp::

        (in-package :com.example.consfig)
        (in-consfig :com.example.consfig)
	(named-readtables:in-readtable :interpol-syntax)

	;; (try-register-data-source
        ;;  :pgp :location #P"/path/to/com.example.consfig.gpg")

        (defhost athena.example.com
          "Web and file server."
          (etc-default:set "locale" "LANG" "en_GB.UTF-8"))

        (defhostdeploy :ssh athena.example.com)

6. Get a Lisp REPL started up -- ``M-x slime`` in Emacs or ``sbcl`` at a shell
   prompt.  Evaluate ``(asdf:require-system "com.example.consfig")``.

7. Now you should be able to use configure athena by evaluating
   ``(com.example.consfig:athena.example.com)``.  You can use the
   ``CONSFIGURATOR:DEPLOY`` function to try out configuring athena using a
   different connection type than defined here.

Portability and stability
=========================

- **Consfigurator is still stabilising and so there may be lots of breaking
  changes.**

- No attempt is made to support Common Lisp implementations other than SBCL,
  though portability patches are welcome.

- Little attempt is made by the author to support systems other than Debian
  GNU/Linux, but again, portability patches are welcome.

Credits
=======

Many of the good ideas here come straight from Joey Hess's Propellor_.  I'm
working on Consfigurator because I think Propellor is great, but wanted to add
Consfigurator's POSIX-type connections and arbitrary connection nesting, and I
wanted to implement that in Lisp (Propellor only supports something equivalent
to a single, unnested Lisp-type connection).  Additionally, after five years
of using and extending Propellor, I've come to disagree with Joey about
whether Haskell's type system helps or hinders using and extending Propellor.

.. Propellor_: https://propellor.branchable.com/