Railsインストール時にnokogiriでコケた話

rbenvも入った、Rubyも入った、さぁRailsだと喜び勇んで、

gem install rails

をしたものの、途中まで順調に行くのに以下のエラーで止まる。

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.

    /home/vagrant/.rbenv/versions/2.2.0/bin/ruby -r ./siteconf20150215-24447-fy001c.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 /home/vagrant/.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 '/home/vagrant/.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=/home/vagrant/.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
/home/vagrant/.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 /home/vagrant/.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 /home/vagrant/.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 /home/vagrant/.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 /home/vagrant/.rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/gems/nokogiri-1.6.6.2 for inspection.
Results logged to /home/vagrant/.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

いろいろ情報だだ洩れな気もするけど気にしない。
ググるとNokogiriで苦しんでる人が多数いるようだけど、
どうもBandlerとかなんとか、使ってないものを使った場合の記事が多い。

途方に暮れつつ、とりあえずエラーメッセージを読んで、

gem install nokogiri -- --use-system-libraries

が有効だと書いてあるので試してみる…も失敗。

そもそもシステムにあるライブラリを使うにしても、
必要なライブラリ入ってないんじゃないか？ってことで、
引っかかっているlibxml2を手動でインストールする。

んで、もっかいgem install nokogiri...をすると成功。

あとはRailsを入れるだけ。

gem install rails

結構時間がかかるので気長に待つ。