This article lists data of interest that should go into a minimal backup of a DokuWiki Installation
The complete list is available on the backup documentation page
To avoid a DDOS with image processing, Dokuwiki adds a signature.
The signature is the value of the tok Url property.
This is:
data\meta\_htcookiesalt
data\meta\_htcookiesalt2
If you are using a cache, don't forget to back up this file well otherwise the images will not show up.
The detailed function is the media_get_token in media.php