The necessary source files for compiling Nginx are not installed. <% if PhusionPassenger.packaging_method == "deb" %> Please install them with: sudo apt-get install <%= DEB_DEV_PACKAGE %> <% elsif PhusionPassenger.packaging_method == "rpm" %> Please install them with: sudo yum install <%= RPM_DEV_PACKAGE %>-<%= VERSION_STRING %> <% else %> Please ask your operating system vendor how to solve this problem. <% end %>