安装redmine遇到的一些问题
遇到问题之一：

RAILS_ENV=production rake db:migrate

rake aborted!
no such file to load -- openssl

解决：
A. yum install openssl-devel
B. 安装ruby的openssl扩展
Linux代码
cd /ruby_sourcecode_dir/ext/openssl
ruby ./extconf.rb
make
make install

遇到问题之二：

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

解决：
yum install mysql-devel
gem install mysql -- --with-mysql-config=/usr/lib/mysql/mysql_config
成功