mysqlモジュールのロードでエラーが発生

[mikoto20000]

次のようなエラーが出て、Redmine(mod_passenger経由)が起動しません＞＜

A source file that the application requires, is missing.
It is possible that you didn't upload your application files correctly. Please check whether all your application files are uploaded.
A required library may not installed. Please install all libraries that this application requires.
Further information about the error may have been written to the application's log file. Please check it in order to analyse the problem.

Error message:
cannot load such file -- mysql (MissingSourceFile)

Exception class:
PhusionPassenger::UnknownError

Application root:
/opt/alminium

Backtrace:
#   File    Line    Location
0   /usr/lib64/ruby/gems/1.9.1/gems/activesupport-2.3.14/lib/active_support/dependencies.rb 184 in `require'
1   /usr/lib64/ruby/gems/1.9.1/gems/activesupport-2.3.14/lib/active_support/dependencies.rb 184 in `require'
2   /usr/lib64/ruby/gems/1.9.1/gems/activesupport-2.3.14/lib/active_support/core_ext/kernel/requires.rb 7   in `block in require_library_or_gem'
3   /usr/lib64/ruby/gems/1.9.1/gems/activesupport-2.3.14/lib/active_support/core_ext/kernel/reporting.rb    11  in `silence_warnings'

mysqlのロードに失敗しているようだが、irbで読み込みを実行すると

# irb
irb(main):001:0> require 'mysql'
=> true

と表示され、モジュールの読み込み自体は成功しているように見えます。う～ん、なんだろ、、、

[mikoto20000]

config/database.ymlを

production:
-  adapter: mysql
+ adapter: mysql2
  database: alminium
  host: localhost

と変更することにより、解決。