Today I installed Ruby 1.9.X on a Debian Linux Server. Worked pretty smoothy with “apt-get install ruby1.9.X”. After “gem1.9.1 install rails” I got this Exception:
custom_require>:29:in `require': no such file to load -- mkmf (LoadError)
If you get this error you have to install two more things:
apt-get install ruby1.9.1-dev apt-get install make
After this update I could install rails.