Ubuntu 14.04 Rails missing file - ruby-on-rails

Question

when installing Rails, everything was good but then, i write:
rails -v
and the output:
/home/toshiba/.rvm/rubies/ruby-2.2.1/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- rails/cli (LoadError)
from /home/toshiba/.rvm/rubies/ruby-2.2.1/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
from /usr/bin/rails:7:in `<main>'
everyone know how to do it?
I used this tutorial: http://installfest.railsbridge.org/
and yes, i run:
gem install rails
I noticed that when i run install rails this thing is pop up
Building native extensions. This could take a while...
ERROR: Error installing rails:
ERROR: Failed to build gem native extension.
/home/toshiba/.rvm/rubies/ruby-2.2.1/bin/ruby -r ./siteconf20150816-3818-sm5w21.rb extconf.rb
checking if the C compiler accepts -ggdb3 -O0 -std=c99 -Wall -Werror... yes
Building nokogiri using packaged libraries.
checking for gzdopen() in -lz... no
zlib is missing; necessary for building libxml2
*** 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=/home/toshiba/.rvm/rubies/ruby-2.2.1/bin/$(RUBY_BASE_NAME)
--help
--clean
--use-system-libraries
--enable-static
--disable-static
--with-zlib-dir
--without-zlib-dir
--with-zlib-include
--without-zlib-include=${zlib-dir}/include
--with-zlib-lib
--without-zlib-lib=${zlib-dir}/lib
--enable-cross-build
--disable-cross-build
extconf failed, exit code 1
Gem files will remain installed in /home/toshiba/.rvm/gems/ruby-2.2.1/gems/nokogiri-1.6.6.2 for inspection.
Results logged to /home/toshiba/.rvm/gems/ruby-2.2.1/extensions/x86_64-linux/2.2.0/nokogiri-1.6.6.2/gem_make.out
It seems bad

Answer 1

I've fixed this problem by
sudo apt-get install zlib1g-dev

Answer 2

This pops up in your install process:
zlib is missing; necessary for building libxml2
I guess you need to sudo apt-get install libxml2.
Edit I got downvoted and probably the answer about installing zlib is (more?) correct. I wonder if installing libxml2 (or libxml2-dev) would have helped as well, there was unfortunately no comment about output of that experiment.