Alpine Configuration Framework Design

The Alpine Configuration Framework (ACF) is a mvc-style application for configuring an Alpine Linux device. The primary focus is for a web interface - a light-weight MVC "webmin".

Installation

Installing ACF is really simple. Just type this in your terminal and follow the instructions to setup ACF:

setup-acf

The above script install mini-httpd, create a certificate, starts mini-httpd in HTTPS mode and installs some basic acf-packages. To view ACF, simply browse to your machine https://<hostname>/

Alternately, your existing web server can be used as follows:

• Install the packages acf-core and acf-alpine-baselayout and packages will install to /usr/share/acf.
• Configure your web server to give access to /usr/share/acf/www and run cgi scripts from /usr/share/acf/www/cgi-bin and you should be able to view ACF.

ACF packages page details the available ACF modules and their status. Proceed to Managing ACF page for Managing Your ACF Installation.

Why Haserl + Lua

Other competitors in the arena were Webmin, Ruby on Rails, PHP with templates.

A full webmin (Perl), RoR or PHP implementation each require several MB of installed code, and can have very slow startup times, especially when used in "cgi" mode. After evaluating many options, we found that Lua has the following advantages:

• It is small (typically ~200KB of compiled code)
• It compiles and runs much faster than PHP, Perl^{[Dead Link]} or Ruby
• It provides a "normal" scripting language with features similar to PHP, perl, java, awk, etc.

Haserl + Lua provides a 'good enough' toolset to build a full-featured web application.

Why ACF is MVC

The MVC design pattern is used to separate presentation information from control logic. By MVC we mean:

• Model - code that reads / writes a config file, starts / stops daemons, or does other work modifying the router.
• View - code that formats data for output
• Controller - code that glues the two together

Note the lack of words like: HTML, XML, OO, AJAX, etc. The purpose of ACF's MVC is simply to separate the configuration logic from the presentation of the output.

The flow of a single transaction is:

start -> execute requested function in controller, optionally reading/writing a file using functions in the model -> execute the view to format the output -> end

Every transaction follows this pattern. For ACF developers, the focus should be on getting a model that does a proper job of abstracting the config file into useable entities and then building a controller that presents useable "actions" based on the model. The presentation layer should be last on the priority list.

Of course, as with all MVC designs, the ACF MVC design is not quite 'pure' MVC and has evolved over time. Most of the controller functionality is handled by the framework code. The framework code will also automatically generate views for HTML, JSON, and a few other viewtypes if no view is defined. Also, many model functions are implemented in helper libraries. We have attempted to make it as easy as possible to develop new ACF modules.

For good background information on what ACF attempts to do, please see Terence Parr's paper "Enforcing Strict Model-View Separation in Template Engines" at https://www.cs.usfcs.edu.

ACF Developer's Guides

1. mvc.lua reference - mvc.lua is the core of ACF
2. mvc.lua example - build a simple (command-line) application
3. acf www-controller reference - ACF www application functions
4. acf www-controller example - webify the above examples
5. ACF how to write - Step by step howto for writing ACF modules
6. ACF core principles - Things that are standard across the application
7. LPOSIX - Documentation for the Lua Posix functions
8. ACF Libraries - Document the libraries and common functions
9. Writing ACF Views - Guide for writing a view
10. Writing ACF Controllers - Guide for writing a controller
11. Writing ACF Models - Guide for writing a model

How to contribute

ACF has support for multiple skins. Some example skins available are:

• /usr/share/acf/www/skins/alps/
• /usr/share/acf/www/skins/cloud/
• /usr/share/acf/www/skins/ice/
• /usr/share/acf/www/skins/snow/
• /usr/share/acf/www/skins/wik/

Feel free to contribute in programming css-stylesheets for ACF.

• Make a new skin folder.

  # mkdir -p /etc/acf/skins/myskin

• Create a css file called as the folder.

  # touch /etc/acf/skins/myskin/myskin.css

Now you can start editing your myskin.css.
If you have ACF running on the computer, you can browse to https://<hostname>/cgi-bin/acf/acf-util/skins/read and switch to your new skin (called myskin) and see the results of your changes.

Pack your myskin folder, containing your css file (and images, if there are any).
Send this patch to acf@lists.alpinelinux.org (Note: Don't forget to subscribe before sending your patch)

See also

• Lua 5.1 Reference Manual
• Programming in Lua (first edition)