May, last year, I created an empty draft for this post, because, around that time, I had gone through quite some effort before I got thumbnails for foreign file repos working just right. Now, I’m taking a dive into my MediaWiki working dirs in preparation of the creation of a separate development environment, so it’s a good moment to rehash the past experience (almost as good as when I’d have done it right away).

This is how I configured the foreign file repo to be able to use images uploaded to the English wiki from the Dutch wiki:

$wgHashedUploadDirectory = false;
$wgForeignFileRepos[] = array(
    'class' => 'ForeignDBRepo',
    'name' => 'en',
    'url' => "",
    'hashLevels' => 0,
    //'thumbScriptUrl' => "",
    'transformVia404' => true,//!$wgGenerateThumbnailOnParse,
    'dbType' => $wgDBtype,
    'dbServer' => $wgDBserver,
    'dbUser' => $wgDBuser,
    'dbPassword' => $wgDBpassword,
    'dbName' => 'hardwood',
    'tablePrefix' => 'mw_',
    'hasSharedCache' => false,
    'descBaseUrl' => '',
    'fetchDescription' => false

To make thumbnails be generated by thumb.php on request I added the following to my .htaccess at the other end (and visa versa, because the Dutch wiki actually contains most of the images):

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^media/thumb/([^/]+)/([0-9]+)px-.*$ /thumb.php?f=$1&width=$2 [L,QSA]