Permission denied rendering thumbnail

[Adam Lewis]

Deploying 4.1 was easy with Docker. Logged in and uploaded some pictures no problem. At first, only saw placeholders with no thumbnail image and now receiving the error below. Not sure where to go from here.An exception has been thrown during the rendering of a template ("Failed to create "/var/alchemy/Phraseanet/www/thumbnails/83/1f": mkdir(): Permission denied."). Failed to create "/var/alchemy/Phraseanet/www/thumbnails/83/1f": mkdir(): Permission denied.