problema ao instalar nokogiri 1.8.4 (Ubuntu 18.04.1 LTS)

ProgrammerCookie
(usa Ubuntu)

Enviado em 19/09/2018 - 22:05h

Eu estava instalando o framework do metasploit. até então, tudo bem, depois disso eu executei o comando ./msfconsole para executar ... e recebi um erro como este:

Could not find nokogiri-1.8.4 in any of the sources
Run `bundle install` to install missing gems.

Eu já percebi que eu iria enfrentar um problemão, porque eles pediram para executar a instalação do pacote de comando .. "bundle install"
Eu me apresentei e apareci isso:

root@elias:/opt/metasploit-framework# bundle install
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/...........
Using rake 12.3.1
Using Ascii85 1.0.3
Using concurrent-ruby 1.0.5
Using i18n 0.9.5
Using minitest 5.11.3
Using thread_safe 0.3.6
Using tzinfo 1.2.5
Using activesupport 4.2.10
Using builder 3.2.3
Using erubis 2.7.0
Using mini_portile2 2.3.0
Fetching nokogiri 1.8.4
Installing nokogiri 1.8.4 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

current directory: /var/lib/gems/2.5.0/gems/nokogiri-1.8.4/ext/nokogiri
/usr/bin/ruby2.5 -r ./siteconf20180919-15212-ttafli.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/2.5.0/gems/nokogiri-1.8.4 for inspection.
Results logged to /var/lib/gems/2.5.0/extensions/x86_64-linux/2.5.0/nokogiri-1.8.4/gem_make.out

An error occurred while installing nokogiri (1.8.4), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.8.4' --source 'https://rubygems.org/'` succeeds before bundling.

In Gemfile:
factory_bot_rails was resolved to 4.11.1, which depends on
railties was resolved to 4.2.10, which depends on
actionpack was resolved to 4.2.10, which depends on
actionview was resolved to 4.2.10, which depends on
rails-dom-testing was resolved to 1.0.9, which depends on
nokogiri
root@elias:/opt/metasploit-framework#

Já pesquisei 200 sites em Português e Inglês etc. Nenhum me ajudou, não consigo instalar nokogiri de forma alguma. Já tentei:

gem install nokogiri
gem installl nokogiri -v '1.8.4'
gem install nokogiri -v '1.8.4' --source 'https://rubygems.org/'

Eu já tentei várias outras formas também, eu já dei atualização no nokogiri não deu certo. Já atualizei tudo, mesmo assim não consegui resolver o problema. alguém ai que consiga este problema pode me ajudar?

obs: Todos os comandos acima foram com permissão root.