尝试安装mysql客户端头文件包，如下所示：

  sudo apt-get install libmysqlclient-dev 
 

您需要package build-essential （由sarnold在评论中建议）

更多信息： http://rubydoc.info/gems/mysql2/0.3.13/frames p>

Ubuntu 10.10

Everything worked fine untill i tried to install a plugin, something went very wrong with mysql2. I tried te remove and reinstall it with this result:

gem install mysql2
Building native extensions.  This could take a while...
ERROR:  Error installing mysql2:
    ERROR: Failed to build gem native extension.

        /home/ruben/.rvm/rubies/ruby-1.9.2-p136/bin/ruby extconf.rb
checking for rb_thread_blocking_region()... *** 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/ruben/.rvm/rubies/ruby-1.9.2-p136/bin/ruby
/home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:368:in `try_do': The complier failed to generate an executable file. (RuntimeError)
You have to install development tools first.
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:435:in `try_link0'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:440:in `try_link'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:552:in `try_func'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:797:in `block in have_func'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:693:in `block in checking_for'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:280:in `block (2 levels) in postpone'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:280:in `block in postpone'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:276:in `postpone'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:692:in `checking_for'
    from /home/ruben/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/mkmf.rb:796:in `have_func'
    from extconf.rb:9:in `<main>'


Gem files will remain installed in /home/ruben/.rvm/gems/ruby-1.9.2-p136/gems/mysql2-0.2.6 for inspection.
Results logged to /home/ruben/.rvm/gems/ruby-1.9.2-p136/gems/mysql2-0.2.6/ext/mysql2/gem_make.out

Hope someone can help! Do not have the time to reinstall my whole server!

Try to install the mysql client header package like this :

sudo apt-get install libmysqlclient-dev

You need package build-essential (suggested by sarnold in comments).

more informations here : http://rubydoc.info/gems/mysql2/0.3.13/frames