安装Redmine2.3.0时，需要安装Mysql2 0.3.11，总是安装失败，显示以下信息：
[root@cloudop redmine-2.3.0]# gem install mysql2
Building native extensions. This could take a while...
ERROR: Error installing mysql2:
ERROR: Failed to build gem native extension.
/usr/local/bin/ruby extconf.rb
checking for rb_thread_blocking_region()... no
checking for rb_wait_for_single_fd()... no
checking for mysql.h... no
checking for mysql/mysql.h... no
-----
mysql.h is missing. please check your installation of mysql and try again.
-----
*** 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/bin/ruby
--with-mysql-config
--without-mysql-config
Gem files will remain installed in /usr/local/lib/ruby/gems/1.8/gems/mysql2-0.3.11 for inspection.
Results logged to /usr/local/lib/ruby/gems/1.8/gems/mysql2-0.3.11/ext/mysql2/gem_make.out我是Redhat5.5的系统，查了下资料，通过更新mysql的库来解决了：
# yum install mysql-devel
# gem install mysql2
