How to install mysql2 on Ubuntu 16.04 [ ERROR: Error installing mysql2: ERROR: Failed to build gem native extension.]
<p>I don't know install mysql2 on ubuntu :( </p>

<pre><code>sudo gem install mysql2
Building native extensions.  This could take a while...
ERROR:  Error installing mysql2:
ERROR: Failed to build gem native extension.

current directory: /var/lib/gems/2.3.0/gems/mysql2-0.4.4/ext/mysql2
/usr/bin/ruby2.3 -r ./siteconf20160515-9715-1s2u1sj.rb extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h

extconf failed, exit code 1

Gem files will remain installed in /var/lib/gems/2.3.0/gems/mysql2-0.4.4 for inspection.
Results logged to /var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/mysql2-0.4.4/gem_make.out
</code></pre>

<p><strong>sudo apt-get install libmysqlclient-dev</strong></p>

<pre><code>Lendo listas de pacotes... Pronto
Construindo árvore de dependências       
Lendo informação de estado... Pronto
libmysqlclient-dev is already the newest version (5.7.12-0ubuntu1).
0 pacotes atualizados, 0 pacotes novos instalados, 0 a serem removidos e 61 não atualizados.
</code></pre>

<p><strong>but is not working</strong></p>