title: error installing rmagick gem on RHEL - ERROR: Failed to build gem native extension
body: <p>i m trying to install snorby on RHEL.
  it asked for ruby, i tried that now i am stuck with rmagick error.</p>
  
  <p>please help.</p>
  
  <pre><code>        Installing rmagick (2.13.1) with native extensions
             Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
              /usr/local/bin/ruby extconf.rb
           checking for Ruby version &gt;= 1.8.5... yes
            extconf.rb:128: Use RbConfig instead of obsolete and deprecated Config.
            checking for gcc... yes
             checking for Magick-config... yes
      checking for ImageMagick version &gt;= 6.4.9... yes
  checking for HDRI disabled version of ImageMagick... yes
  Package MagickCore was not found in the pkg-config search path.
  
  Perhaps you should add the directory containing `MagickCore.pc'
  to the PKG_CONFIG_PATH environment variable
  No package 'MagickCore' found
  
             Package MagickCore was not found in the pkg-config search path.
              Perhaps you should add the directory containing `MagickCore.pc'
             to the PKG_CONFIG_PATH environment variable
                No package 'MagickCore' found
           Package MagickCore was not found in the pkg-config search path.
     Perhaps you should add the directory containing `MagickCore.pc'
     to the PKG_CONFIG_PATH environment variable
  No package 'MagickCore' found
  
  Package MagickCore was not found in the pkg-config search path.
  Perhaps you should add the directory containing `MagickCore.pc'
  to the PKG_CONFIG_PATH environment variable
  
         No package 'MagickCore' found
          checking for stdint.h... yes
           checking for sys/types.h... yes
         checking for wand/MagickWand.h... no
  
        Can't install RMagick 2.13.1. Can't find MagickWand.h.
        *** 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
          --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/bin/ruby
  
  
         Gem files will remain installed in                        
   /var/www/html/snorby/vendor/bundle/ruby/1.9.1/gems/rmagick-2.13.1 for inspection.
  
  Results logged to /var/www/html/snorby/vendor/bundle/ruby/1.9.1/gems/rmagick-
  
     2.13.1/ext/RMagick/gem_make.out
  
  An error occured while installing rmagick (2.13.1), and Bundler cannot continue.
  Make sure that `gem install rmagick -v '2.13.1'` succeeds before bundling. `
  </code></pre>