Manual:Wiki family

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A wiki family is a collection of two or more wikis that run on the same server and share a common set of resources from the parent installation, while each wiki remains otherwise independent. This setup is an alternative to running fully separate installations of MediaWiki. It may be the preferred choice if the site admin wants to reduce the amount of work involved in managing multiple wikis, or cut down on inode usage. For this reason, some wiki hosting services opt for the wiki family model.

The best known implementation of a wiki family is the wiki farm, although other approaches are possible. A list of known wiki farms is available on WikiApiary .

Below are instructions for how to set up MediaWiki to host more than one wiki.

Methods

Wiki farm

The following steps are for running multiple wikis on same version of MediaWiki:

Install the first wiki as normal. For details, see Manual:Installation guide .
Enable your web server to share your MediaWiki install with all wikis. For multiple (sub)domains, have your web server accept connections from all the relevant domains. For multiple subdirectories, you could use rewrite rules, aliases, or symlinks.

Add code to the top of LocalSettings.php, to detect the current wiki. Note that if the argument to --wiki contains a hyphen, the argument will be split on the hyphen and the resulting two values assigned to MW_DB and MW_PREFIX, respectively. For wikis by domain name:

$wikis = [
    'example.org' => 'examplewiki',
    'one.example.org' => 'onewiki',
];
if ( defined( 'MW_DB' ) ) {
    // Automatically set from --wiki option to maintenance scripts
    $wikiID = MW_DB;
} else {
    // Use MW_DB environment variable or map the domain name
    $wikiID = $_SERVER['MW_DB'] ?? $wikis[ $_SERVER['SERVER_NAME'] ?? '' ] ?? null;
    if ( !$wikiID ) {
        die( 'Unknown wiki.' );
    }
}

$wgLocalDatabases = $wgConf->wikis = array_values( $wikis );
$wgDBname = $wikiID;
$wgDBuser = 'mediawiki';

Configure settings that must differ for all wikis. For example:

$wgCacheDirectory = "/tmp/mediawiki_cache/$wgDBname";
$wgUploadDirectory = "$IP/images/$wgDBname";
$wgUploadPath = "/w/images/$wgDBname";

Configure per-wiki overrides. This should include at least $wgServer and $wgArticlePath.

$wgConf->settings = [
    'wgServer' => [
        'examplewiki' => 'https://example.org',
        'onewiki' => 'https://one.example.org',
    ],
    'wgArticlePath' => [
        'default' => '/wiki',
    ],
    'wgSitename' => [
        'default' => 'Example',
        'onewiki' => 'One',
    ],
    'wgLogo' => [
        'default' => '/images/examplewiki/Example_logo.png',
    ],
    'wgLanguageCode' => [
        'default' => 'en',
        'onewiki' => 'pt',
    ],
];
extract( $wgConf->getAll( $wgDBname  ) );

This could be done from a separate file, e.g.:

# LocalSettings.php
$wgConf->settings = require __DIR__ . '/LocalSettings_overrides.php';

# LocalSettings_overrides.php
<?php
return [
    'wgServer' => ..,
    ..,
];

To add a new wiki to the family:

Create its database and add its settings first , with --wiki=mywiki if you run install.php from the command line.
Run php maintenance/update.php --wiki=mywiki.

Separate settings files

This approach is for operating entirely independent wikis, but still sharing the same web server and MediaWiki source code.

Install the first wiki as normal, via the web or CLI installer, which sets up your database and generates a LocalSettings.php file.
After installation, rename the generated LocalSettings.php file to include the wiki ID (e.g. database name), like LocalSettings_mywiki.php.
Repeat step one and two above for each wiki you wish to create.

Create a new LocalSettings.php file that will load the correct one. As with the above wiki farm example, a --wiki argument containing a hyphen will be split on the hyphen into two values assigned to MW_DB and MW_PREFIX, respectively.

<?php
$wikis = [
    'example.org' => 'examplewiki',
    'one.example.org' => 'onewiki',
];
if ( defined( 'MW_DB' ) ) {
    // Automatically set from --wiki option to maintenance scripts
    $wikiID = MW_DB;
} else {
    // Use MW_DB environment variable or map the domain name
    $wikiID = $_SERVER['MW_DB'] ?? $wikis[ $_SERVER['SERVER_NAME'] ?? '' ] ?? null;
}

if ( $wikiID ) {
    require_once "LocalSettings_$wikiID.php";
} else {
    die( 'Unknown wiki.' );
}

// Add any settings that should apply to all wikis below this line
// -------

If your wikis are on the same domain but under different paths (e.g. example.org/wiki1, example.org/wiki2 etc.), you can use something like this:

<?php
$wikis = [
    '/example' => 'examplewiki',
    '/w_example' => 'examplewiki',
    '/one' => 'onewiki',
    '/w_one' => 'onewiki',
];
if ( defined( 'MW_DB' ) ) {
    // Automatically set from --wiki option to maintenance scripts.
    $wikiID = MW_DB;
} else {
    $path = explode( '/', $_SERVER['REQUEST_URI'] ?? '', 3 )[1] ?? '';
    $wikiID = $_SERVER['MW_DB'] ?? $wikis[ $path ] ?? null;
}

if ( $wikiID ) {
    require_once "LocalSettings_$wikiID.php";
} else {
    die( 'Unknown wiki.' );
}

If you use Short URL, you need to add both your $wgArticlePath and the $wgScriptPath.

Drupal-style sites

This setup has the advantage of being completely transparent to users and reasonably secure in terms of the images directory.

Create a base directory to contain all your MediaWiki files e.g. mkdir /home/web/mediawiki.
Install MediaWiki and additional tools as usual to a version-declaring subdirectory (e.g., /home/web/mediawiki/mediawiki-1.10.0).
Link the version-declaring directory to a code directory. e.g., ln -s /home/web/mediawiki/mediawiki-1.10.0 /home/web/mediawiki/code
Create a sites directory to contain our images and settings: mkdir /home/web/mediawiki/sites
Setup the wiki as normal from the /code directory.
After successful installation, move LocalSettings.php into a sites directory that will be a match when the site is checked. For example, to capture http://example.com/mywiki, one would create the directory example.com.mywiki. e.g., mkdir /home/web/mediawiki/sites/example.com.mywiki. See the Drupal's settings.php file for more information on this.
If you intend to use media files, create an images directory in your site directory. e.g., mkdir /home/web/mediawiki/sites/example.com.wiki/images. Make it writable as necessary.
Place the Drupal-style LocalSettings.php file in your main directory: cp DrupalLocalSettings.php /home/web/mediawiki/code/LocalSettings.php
Modify the LocalSettings.php of each subsite to point to the right places:
1. First comment out the code relating to $IP, (lines 16-20 in 1.15.3) as this is set to the code directory by index.php.
2. Next insert the following two lines to ensure that image files are accessible, e.g.: $wgUploadDirectory = "/home/web/mediawiki/sites/wiki.example.com/images"; and $wgUploadPath = "/images";. These need to be put somewhere after the call to DefaultSettings.php (line 25 in 1.15.3), as the variables will otherwise be reset.
3. Make further modifications as required.

Prepare your Apache 2 installation. Example site: wiki.example.com

Create a link to the code directory, if required e.g. ln -s /home/web/mediawiki/code /home/web/wiki.example.com

Create an appropriate virtual host configuration:

<VirtualHost *:80>
    ServerAdmin me@example.com
    DocumentRoot /home/web/wiki.example.com
    ServerName wiki.example.com
    CustomLog /var/log/apache2/wiki.mysite.log common
    # Alias for the site to be accessible
      Alias /mediawiki/code /home/web/mediawiki/code
    # Alias for wiki so images work
      Alias /images /home/web/mediawiki/sites/wiki.example.com/images
    # If you want to password protect your site
    #  <Directory /home/web/wiki.example.com>
    #    AuthType Basic
    #    AuthName "My protected wiki"
    #    AuthUserFile /etc/apache2/htpasswd/users-mywiki
    #   require valid-user
    #  </Directory>
</VirtualHost>

11. If you are setting the sites up locally, update your hosts file with the site names. The site should now work.

In my case, I made another copy of the code from which to install and update my LocalSettings.php and databases. Note that $_SERVER['HTTP_HOST'] in the companion Drupal code is undefined when running maintenance scripts from the command line, so this solution does not permit the use of maintenance scripts without some modification.

Modified Drupal-style method for Ubuntu

A simplified method for multiple wikis and multiple (or nested) subwikis on Ubuntu/Kubuntu that is loosely based on the above method can be found at:

Ubuntuguide.org MediaWiki tips

How wiki farms are handled in maintenance scripts

MediaWiki maintenance scripts (e.g. update.php) accept a --wiki argument that is passed to your LocalSettings.php file as the constants MW_DB, MW_PREFIX, and MW_WIKI_NAME. The entire value of the --wiki argument is the value of MW_WIKI_NAME.

If there is a dash in the --wiki argument, then the part before the dash is assigned to MW_DB and the part after the dash is assigned to MW_PREFIX.

This table demonstrates how this works:

How the `--wiki` argument is parsed.
`--wiki`	`MW_WIKI_NAME`	`MW_DB`	`MW_PREFIX`
enwiki	enwiki	enwiki	empty
enwiki-one	enwiki-one	enwiki	one
enwiki-one-two	enwiki-one-two	enwiki	one-two

Since there is no --wiki argument for web requests, they must be handled differently. Typically, the domain name and/or URL path is used to select a wiki.

Tips for sharing between wikis

You can use $wgForeignFileRepos to share uploaded media files across wikis. This is similar to Wikimedia Commons for Wikipedia.

For example:

en.example.org - English
fr.example.org - French
de.example.org - German
pool.example.org - Shared media files for all wikis.

The above example uses the name "pool". Avoid using the name "commons" because this may conflict with the interwiki link also named commons for Wikimedia Commons. Also avoid using the name "media" (e.g. media.example.org) as that may cause a conflict between your interwiki and the internal namespace Media: for accessing local media files, e.g. [[media:File.png]].

Shared database tables

Consider using a shared database for user accounts. See Manual:Shared database for instructions on setting up shared database tables.

Interwiki

You can create interwiki links between all wikis, by using Extension:Interwiki . If the wikis are language editions, it is recommended to name the interwiki prefix after the exact language code. For example, "de" for the German wiki in your family. This way, you can connect pages about the same subject using language links.

Adding [[de:Hauptseite]] on your English "Main Page" will create a link "Deutsch" in the languages sidebar. For further information visit Help:Interwiki linking

If you have a central wiki for files, create a prefix for this as well. E.g. pool to https://pool.example.org/wiki/$1 and enable the "Forward" checkbox to recognise it as a local wiki in the same family.

Upload

Make sure that folder "images" of the pool-wiki is writable.

It is useful to change the "Upload file"-Link of the language-wikis to point to poolwiki's upload-site. Open the "LocalSettings.php" of each language-wiki and add:

$wgUploadNavigationUrl = "https://pool.example.org/index.php/Special:Upload";

In 1.17, you'll also have to set $wgUploadMissingFileUrl to be redirected to the pool-wiki on red links.

$wgUploadMissingFileUrl= "https://pool.example.org/index.php/Special:Upload";

If you want to allow uploads only for your pool wiki, you may use something like this:

if ( $wgDBname === 'pool' ) {
	$wgEnableUploads = true;
} else {
	$wgEnableUploads = false;
}

Use shared files

To use poolwiki's files in the languagewikis, open "LocalSettings.php" for each languagewiki and add:

$wgUseSharedUploads = true;
$wgSharedUploadPath = 'https://pool.example.org/images';
$wgSharedUploadDirectory = '/(LOCALPATH)/POOL-FOLDER/images/';
$wgHashedSharedUploadDirectory = true;

Now you can integrate pool's files with (e.g. [[File:MyLogo.png]]) in the languagewikis.

Image description

In each languagewiki, open (as an admin) the message MediaWiki:Sharedupload-desc-here.

Change the text to something like:

This file is stored in our data-pool.
For information and description, please visit the [[:pool:File:{{PAGENAME}}|description there]].

(And note the ':' at the beginning of the line, which stops 'pool' from being included in the interwiki list at the left of the page.)

If you want to output the media-description, stored in the PoolWiki, too, add to the "LocalSettings.php" of the languagewikis:

$wgFetchCommonsDescriptions = true;
$wgSharedUploadDBname = 'pool';  # DB-Name of PoolWiki
$wgSharedUploadDBprefix = 'wiki_'; # Table name prefix for PoolWiki
$wgRepositoryBaseUrl = "https://pool.example.org/index.php/Image:";

Wiki Farm extensions

There are several MediaWiki extensions that attempt to simplify hosting of several wikis by using just one code base, however only one is currently noteworthy:

Extension:MediaWikiFarm - beta.

Extension:SkinCustomiser : For localisation issues of the Sidebar and customising the Skins regarding the files MediaWiki:Cologneblue.css, MediaWiki:Modern.css, MediaWiki:Monobook.css, MediaWiki:Vector.css, MediaWiki:Mobile.css, MediaWiki:Common.css respectively.