shetty@shetty-laptop:~$ sudo gem install rmagick
[sudo] password for shetty:
Building native extensions. This could take a while...
ERROR: Error installing rmagick:
ERROR: Failed to build gem native extension.
/usr/bin/ruby1.8 extconf.rb install rmagick
extconf.rb:1:in `require': no such file to load -- mkmf (LoadError)
from extconf.rb:1
mkmf.rb 是ruby1.8-dev package 的一部分,安装ruby1.8-dev就可以了
sudo apt-get install ruby1.8-dev