To share the users list in a “farm” setup in DokuWiki, meaning when you have multiple wikis running off of one codebase, you must add this code:
$config_cascade['plainauth.users'] = array( 'default' => '/your/path/to/conf/users.auth.php', );
to inc/preload.php
and it must come after this line:
include(fullpath(dirname(__FILE__)).'/farm.php');