User:Aeric/Configuration

How the Wiki Works

Major concepts:

• Mediawiki consists of a MySQL database, plus a collection of PHP scripts and supporting files in the Wiki directory.
• The textual Wiki content is contained in a database.
• Image files are stored in a hashed system of nested directory folders under {wiki}/images. (The database contains links to them.)
• Together, the database plus the files and scripts contained in the wiki's directory folder make up the Wiki that the user sees.

The main configuration script:

LocalSettings.php

• $wgDBname - The variable that names the database in the MySQL space,

accompanied by the login information and the mysql "secret key" for the space

• $wgScriptPath - This variable is used to generate Wiki links. E.g. "/wiki".

The wiki will start if it's wrong, but all of the links it generates will point to this location. Much internal processing will look there for scripts, as well.

Standard directories:

extensions/

MediaWiki plug-ins that have been downloaded and "installed" by referencing them in LocalSettings.php. (Since pages are loaded dynamically, once the extension is present, it is automatically part of the Wiki. No restart needed.)

images/

A directory hierarchy that contains the image files after they have been uploaded. The Wiki stores them there when you upload an image, and keeps a pointer to them in the database.

skins/

The images and CSS files that create the "wrapper context" (headers, nav pane, etc.) for the wiki content. (The lj7monobook skin was customized to make the nav pane wider.)

Added directories:

_v16_skins/

A copy of the skins that came with MW 1.16.5, before the nav pane was widened. Saved so that a diff tool can be used to identify those changes and any others.

custom_images/

Header images and favicons used by the browser for bookmarks and tabs.

download/

A directory we added to hold files we want to reference in the wiki. (Only image files can be uploaded to the Wiki. But that's ok. Image loads are done painfully, one at a time. Files in the download/ folder can be easily updated en mass. (Image files need to be uploaded so that "links" to them coded in the wiki cause the image to be displayed.)

How Links to the Wiki Work

The mapping of URLs to Wiki's is set up in the mediawiki.conf file, which will be discussed momentarily.

Current Version Links

These URLS always point to the latest released version of the Support Wiki:

http://{subdomain}.agileappslive.info/wiki - AgileApps Live support wiki

http://{subdomain}.platformatyourservice.com/wiki - Legacy LongJump wiki

Those are the best links to send to current customers, as they’ll always point to the latest pages. And they will always stay at the top of the Google search rankings, by virtue of being the most heavily accessed Wiki pages.

Versioned links

Customers with an on-premise installation need to refer to a version of the wiki that matches their installation:

http://{subdomain}.agileappslive.info/aa90

http://{subdomain}.platformatyourservice.com/lj82

Use scripts/versionProductionWiki to create an versioned copy of the production wiki when an installable version is released.

Pre-Release Links

To review a pre-release version of AAL content, use this link:

http://{subdomain}.agileappslive.info/mw_dev

That link points to the "development" (pre-release) version of the wiki.

(Since updates happen every three or four weeks, customers will rarely need it.)

Server Configuration

Configuration Notes

• The wiki is hosted at Rackspace.
• The server can be accessed with a VPN connection, using either FTP or SSH.

FTP gives access to all of the Wiki files, which is generally sufficient.

(Access details are in emails.)

• DNS entries that point to the server are agileappslive.info and platformatyourservice.com.
• Location of any given wiki is /usr/share/mediawiki/{wikiName}
• Multiple subdomains are set up using Apache, the DNS server, and LocalSettings.php.
• The DNS entries determine which subdomains are known to the world.
• The wiki name in the url determines which wiki is accessed. (E.g. /wiki)
• The LocalSettings.php file in that wiki uses the subdomain to determine which skin is used.
• The skin determines which logo is shown, which platform name to use, and the settings for several other variables, including the site name.

Organization of the mediawiki.conf Configuration File

• There are two <VirtualHost> sections, one for each virtual server:
  (agileappslive.info and platformatservice.com).

• Inside each virtual host, there is a <Directory> section for each wiki that can be accessed, as well as an Alias setting that maps the {domain}/xyz URL to the /usr/share/mediawiki/xyz wiki folder.

• In the AgileAppsLive domain, the "/wiki" alias points to the mw_prod wiki, as does the "/mw_prod" alias.

• When scripts/versionProductionWiki is run to make a versioned copy of the production wiki, a new directory-section and alias are created for it. E.g. "aa90".

• Each <Directory> contains a number of URL rewrites that are needed to make the wiki work properly. Unfortunately, they need to be copied for each directory.

• Attempts to do global rewrites failed, as recorded in notes at the top of the file. However, the rewrites were not attempted inside the <VirtualHost> headings, as those came later.
• So it is possible that a clever configuration could cut down the size of the <Directory> segments.
• But, as the notes in the file attest, the Apache rewrites frequently do not work as documented--so the actual semantics must be discovered by trial and error. (A rainy day project for sure, not worth the time given that we have a working system.)

Configuring Apache

• The Apache configuration file is /etc/httpd/conf.d/mediawiki.conf.

• Always preserve the original and edit a copy in /usr/share/mediawiki/apache_config

• To edit, either:

1. SSH to the server using PuTTY or the SSH shell, and use a line-oriented editor like nano.
2. Use FTP to bring the file back to your workstation, and use a terrific editor like NotePad++

Maintenance Scripts

Maintenance scripts in /usr/share/mediawiki/apache_config:

• ./get_conf

Gets a copy of the three main configuration files, primarily for backup:

httpd.conf

phpMyAdmin.conf

mediawiki.conf

• ./try_setup

Copies the current config file as mediawiki.conf_sav.

If no else is editing mediawiki.conf, then mediawiki.conf_new has the same content, and is ready to be edited. Otherwise, copy _sav to _new before you begin.

• ./try

Put mediawiki.conf_new in place and restart the server.

For a quick test, refresh the page for each of the main wikis:

• http://agileappslive.info/wiki
• http://agileappslive.info/mw_dev
• http://lj.platformatyourservice.com/wiki

If you can see the page and the generated links are correct, the wiki is usable.

If you've done any work on the skins, then test the changes, as well

• ./revert

Put mediawiki.conf_sav back in place, in case the _new version didn't work.

Apache References

• http://net.tutsplus.com/tutorials/other/a-deeper-look-at-mod_rewrite-for-apache/
• http://www.addedbytes.com/download/regular-expressions-cheat-sheet-v2/png
• http://www.addedbytes.com/cheat-sheets/mod_rewrite-cheat-sheet/