mod_fcgid module is a high-performance alternative to
mod_cgi and handles all requests for programs (such as Ruby) that need to be executed on the server. This recipe may not be a very popular choice due to the fact that many standalone Ruby servers such as Thin, Puma, and Phusion Passenger now exist. However, it may be required, and it's very reliable and relies only on Apache and Ruby executables.
mod_fastcgidby typing the following:
sudo apt-get install apache2 libapache2-mod-fcgid
Once the prerequisites are installed, and Redmine is confirmed as working with WEBrick, ...