How to fix – MediaWiki Error creating thumbnail: Unable to run external programs in safe mode
This issue happens when Image Magic is enabled. The easiest way to fix it, is to find your LocalSetting.php file and comment out the following lines:
# $wgUseImageMagick = true;
# $wgImageMagickConvertCommand = “/usr/bin/convert”;
Commenting out the “wgUseImageMagic” line will enable thumbnails for the newly uploaded images. Nice and simple!