Railsをインストールできない

Question

##vagrant上でCentOSを使ってRuby on railsのローカル開発環境を構築しようと思っています。

しかし

gem install rails

と打っても

Building native extensions. This could take a while...
ERROR:  Error installing rails:
	ERROR: Failed to build gem native extension.

    current directory: /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/nokogiri-1.10.9/ext/nokogiri
/home/vagrant/.rbenv/versions/2.6.6/bin/ruby -I /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0 -r ./siteconf20200628-1122-1k5kgq1.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=/home/vagrant/.rbenv/versions/2.6.6/bin/$(RUBY_BASE_NAME)
	--help
	--clean
/home/vagrant/.rbenv/versions/2.6.6/lib/ruby/2.6.0/mkmf.rb:467:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
	from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/2.6.0/mkmf.rb:585:in `block in try_compile'
	from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/2.6.0/mkmf.rb:532:in `with_werror'
	from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/2.6.0/mkmf.rb:585:in `try_compile'
	from extconf.rb:138:in `nokogiri_try_compile'
	from extconf.rb:162:in `block in add_cflags'
	from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/2.6.0/mkmf.rb:643:in `with_cflags'
	from extconf.rb:161:in `add_cflags'
	from extconf.rb:416:in `<main>'

To see why this extension failed to compile, please check the mkmf.log which can be found here:

  /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/extensions/x86_64-linux/2.6.0/nokogiri-1.10.9/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/nokogiri-1.10.9 for inspection.
Results logged to /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/extensions/x86_64-linux/2.6.0/nokogiri-1.10.9/gem_make.out

と表示され上手くインストールされません。
不思議なことに

which rails

とすると

~/.rbenv/shims/rails

と表示されます。
しかし

rails -v

とすると

Traceback (most recent call last):
	20: from /home/vagrant/.rbenv/versions/2.6.6/bin/rails:23:in `<main>'
	19: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems.rb:297:in `activate_bin_path'
	18: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems.rb:297:in `synchronize'
	17: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems.rb:298:in `block in activate_bin_path'
	16: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1371:in `activate'
	15: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1389:in `activate_dependencies'
	14: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1389:in `each'
	13: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1403:in `block in activate_dependencies'
	12: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1371:in `activate'
	11: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1389:in `activate_dependencies'
	10: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1389:in `each'
	 9: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1403:in `block in activate_dependencies'
	 8: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1371:in `activate'
	 7: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1389:in `activate_dependencies'
	 6: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1389:in `each'
	 5: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1403:in `block in activate_dependencies'
	 4: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1371:in `activate'
	 3: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1389:in `activate_dependencies'
	 2: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1389:in `each'
	 1: from /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/specification.rb:1400:in `block in activate_dependencies'
/home/vagrant/.rbenv/versions/2.6.6/lib/ruby/site_ruby/2.6.0/rubygems/dependency.rb:311:in `to_specs': Could not find 'nokogiri' (>= 1.5.9) among 104 total gem(s) (Gem::MissingSpecError)
Checked in 'GEM_PATH=/home/vagrant/.gem/ruby/2.6.0:/home/vagrant/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0', execute `gem env` for more information

となってしまいます。
試行錯誤中ですが、アドバイスいただけると嬉しいです。

以前自分でググりながらrbenv,ruby-buildの他にbundleやdevelopment tools、homebrewなども開発環境に入れてしましました。
それも原因かもしれません。

Answer 1

ERROR: Failed to build gem native extension.
current directory: /home/vagrant/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/nokogiri-1.10.9/ext/nokogiri

アドバイスですが、Gem nokogiriのコンパイルに失敗していますね。
nokogiriはC言語で書かれたGemなのであなたの環境でコンパイルできる必要があります。

Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.

エラーメッセージでググって、必要な開発用ライブラリを特定して、インストールしてください。