Yesterday I downloaded the latest Reddit Raw editing challenge files, only to find that I couldn’t open them in the rather dated version of darktable that I was running (on Ubuntu 14.04 Trusty).
The reason for this is that the photo was taken with a Fujifilm X100S, which uses an X-Trans sensor with a different arrangement of RGB filters to the traditional Bayer array.
This different arrangement means that processing the Raw requires different maths and algorithms. These were included in darktable release 1.6.0 in December 2014, but the official Ubuntu repositories for Trusty (Ubuntu 14.04) or Vivid (Ubuntu 15.04) only go up to darktable 1.4.2. So if you were using the official Ubuntu release for darktable, you will not be able to handle Fujifilm Raw files.
(Note that Wily, Ubuntu 15.04, will upgrade darktable to 1.6.7, but is not released until October 2015).
How to open Fujifilm Raw files in darktable on Ubuntu
If you want to edit Fujifilm Raw files in darktable you will need a recent release. One way would be to clone the Github repository of darktable and install from source, but this is a little tricky. A much easier way is to add this repository to your sources for installable software. Pascal de Bruijn maintains versions of the latest darktable releases for Ubuntu there, so once you have added it to your sources, Ubuntu’s package manager will automatically keep darktable updated to the latest version.