Installing SystemTimer (1.2.1) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/usr/bin/ruby extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/ruby.h
Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/SystemTimer-1.2.1 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/SystemTimer-1.2.1/ext/system_timer/gem_make.out
An error occured while installing SystemTimer (1.2.1), and Bundler cannot continue.
Make sure that `gem install SystemTimer -v '1.2.1'` succeeds before bundling.
我看到this post但是mysql不是问题（或者是它？我确实安装了-devel）。
这是在Fedora服务器上安装Diaspora。我之前安装过它，但已迁移到新服务器。另一个是CentOS，目前并不重要。
不确定从哪里开始。我确实尝试了yum list *timer*来查看我需要安装的相同行中是否有任何内容。
谢谢！