■前提条件
・CentOS release 6.4 (Final)
・Ruby 2.2.0
・Rails 4.2.0
・システムワイドな環境の構築
Railsインストール中、下記のようにnokogiriのインストールでコケました。
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# gem install rails
Fetching: thread_safe-0.3.4.gem (100%)
Successfully installed thread_safe-0.3.4
Fetching: tzinfo-1.2.2.gem (100%)
Successfully installed tzinfo-1.2.2
Fetching: i18n-0.7.0.gem (100%)
Successfully installed i18n-0.7.0
Fetching: activesupport-4.2.0.gem (100%)
Successfully installed activesupport-4.2.0
Fetching: rails-deprecated_sanitizer-1.0.3.gem (100%)
Successfully installed rails-deprecated_sanitizer-1.0.3
Fetching: mini_portile-0.6.2.gem (100%)
Successfully installed mini_portile-0.6.2
Fetching: nokogiri-1.6.6.2.gem (100%)
Building native extensions.  This could take a while…
ERROR:  Error installing rails:
	ERROR: Failed to build gem native extension.
    /usr/local/rbenv/versions/2.2.0/bin/ruby -r ./siteconf20150303-26936-1o4ex0z.rb extconf.rb
checking if the C compiler accepts … yes
Building nokogiri using packaged libraries.
checking for gzdopen() in -lz… yes
checking for iconv… yes
************************************************************************
IMPORTANT NOTICE:
Building Nokogiri with a packaged version of libxml2-2.9.2
with the following patches applied:
	– 0001-Revert-Missing-initialization-for-the-catalog-module.patch
	– 0002-Fix-missing-entities-after-CVE-2014-3660-fix.patch
Team Nokogiri will keep on doing their best to provide security
updates in a timely manner, but if this is a concern for you and want
to use the system library instead; abort this installation process and
reinstall nokogiri as follows:
    gem install nokogiri — –use-system-libraries
        [–with-xml2-config=/path/to/xml2-config]
        [–with-xslt-config=/path/to/xslt-config]
If you are using Bundler, tell it to use the option:
    bundle config build.nokogiri –use-system-libraries
    bundle install
Note, however, that nokogiri is not fully compatible with arbitrary
versions of libxml2 provided by OS/package vendors.
************************************************************************
Extracting libxml2-2.9.2.tar.gz into tmp/x86_64-unknown-linux-gnu/ports/libxml2/2.9.2… OK
Running patch with /usr/local/rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/gems/nokogiri-1.6.6.2/ports/patches/libxml2/0001-Revert-Missing-initialization-for-the-catalog-module.patch…
Running ‘patch’ for libxml2 2.9.2… ERROR, review ‘/usr/local/rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/gems/nokogiri-1.6.6.2/ext/nokogiri/tmp/x86_64-unknown-linux-gnu/ports/libxml2/2.9.2/patch.log’ to see what happened.
*** 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=/usr/local/rbenv/versions/2.2.0/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
/usr/local/rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/gems/mini_portile-0.6.2/lib/mini_portile.rb:279:in `block in execute’: Failed to complete patch task (RuntimeError)
	from /usr/local/rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/gems/mini_portile-0.6.2/lib/mini_portile.rb:271:in `chdir’
	from /usr/local/rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/gems/mini_portile-0.6.2/lib/mini_portile.rb:271:in `execute’
	from extconf.rb:311:in `block in patch’
	from extconf.rb:308:in `each’
	from extconf.rb:308:in `patch’
	from /usr/local/rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/gems/mini_portile-0.6.2/lib/mini_portile.rb:108:in `cook’
	from extconf.rb:278:in `block in process_recipe’
	from extconf.rb:177:in `tap’
	from extconf.rb:177:in `process_recipe’
	from extconf.rb:475:in `<main>’
extconf failed, exit code 1
Gem files will remain installed in /usr/local/rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/gems/nokogiri-1.6.6.2 for inspection.
Results logged to /usr/local/rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/extensions/x86_64-linux/2.2.0-static/nokogiri-1.6.6.2/gem_make.out
[/bash]
依存関係のlibxml2とlibxsltがインストールされていないのが原因ですので、
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# yum  install libxml2 libxslt libxml2-devel libxslt-devel
[/bash]
libxml2 libxslt libxml2-devel libxslt-develをインストールします。
次に、nokogiriをインストールし、
[bash gutter=”0″]
# gem install nokogiri
[/bash]
あらためて、
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# gem install rails
[/bash]
railsをインストールします。
これでうまくいくはずです。