gem install mysql2 エラーの対策

経緯

ruby で MySQLを操作するためのプログラムを書きたくて、gemのmysql2をインストールしようとした際にハマったので自分のための備忘録。

環境

Ubuntu16.04
ruby2.3

エラー

admin@hoge:/usr/local/share/update_pdns$ sudo bundle install --path vender/bundle
Don't run Bundler as root. Bundler can ask for sudo if it is needed, and installing your bundle as root will break this application for all non-root users on this machine.
Fetching gem metadata from https://rubygems.org/..............
Fetching version metadata from https://rubygems.org/.
Resolving dependencies...
Using concurrent-ruby 1.0.5
Using i18n 0.8.1
Using minitest 5.10.1
Using thread_safe 0.3.6
Using arel 7.1.4
Using mime-types-data 3.2016.0521
Installing mysql2 0.4.5 with native extensions
Using bundler 1.14.5
Using tzinfo 1.2.2
Using mime-types 3.1
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /usr/local/share/update_pdns/vender/bundle/ruby/2.3.0/gems/mysql2-0.4.5/ext/mysql2
/usr/bin/ruby2.3 -r ./siteconf20170303-8868-1xsjnvm.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 /usr/local/share/update_pdns/vender/bundle/ruby/2.3.0/gems/mysql2-0.4.5 for inspection.
Results logged to /usr/local/share/update_pdns/vender/bundle/ruby/2.3.0/extensions/x86_64-linux/2.3.0/mysql2-0.4.5/gem_make.out

An error occurred while installing mysql2 (0.4.5), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.4.5'` succeeds before bundling.

mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h

どうやら rubyのヘッダーファイルが見つからないとのこと。

対策

$sudo aptitude install ruby-dev

ruby-devパッケージにヘッダーファイルが格納されてるらしい。
これをインストールしたら解決しました！

参考 URL