How to use gem to install Rails on Ubuntu

The error message: Building native extensions. This could take a while... ERROR: Error installing rails: ERROR: Failed to build gem native extension. /usr/bin/ruby2.1 -r ./siteconf20150328-1540-hff2f0.rb extconf.rb checking if the C compiler accepts ... *** extconf.rb failed *** Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check the mkmf.log file for more details. You may need configuration options. Provided configuration options: --with-opt-dir --without-opt-dir --with-opt-include --without-opt-include=${opt-dir}/include --with-opt-lib --without-opt-lib=${opt-dir}/lib --with-make-prog --without-make-prog --srcdir=. --curdir --ruby=/usr/bin/ruby2.1 --help --clean /usr/lib/ruby/2.1.0/mkmf.rb:456:in `try_do': The compiler failed to generate an executable file. (RuntimeError) You have to install development tools first. from /usr/lib/ruby/2.1.0/mkmf.rb:571:in `block in try_compile' from /usr/lib/ruby/2.1.0/mkmf.rb:522:in `with_werror' from /usr/lib/ruby/2.1.0/mkmf.rb:571:in `try_compile' from extconf.rb:80:in `nokogiri_try_compile' from extconf.rb:87:in `block in add_cflags' from /usr/lib/ruby/2.1.0/mkmf.rb:621:in `with_cflags' from extconf.rb:86:in `add_cflags' from extconf.rb:337:in `<main>' extconf failed, exit code 1 Gem files will remain installed in /var/lib/gems/2.1.0/gems/nokogiri-1.6.6.2 for inspection. Results logged to /var/lib/gems/2.1.0/extensions/x86_64-linux/2.1.0/nokogiri-1.6.6.2/gem_make.out Configurations: 1. Ubuntu 14.10 (GNU/Linux 3.16.0-23-generic x86_64) 2. gcc (Ubuntu 4.9.1-16ubuntu6) 4.9.1 3. ruby 2.1.2p95 (2014-05-08) [x86_64-linux-gnu]