This small tutorial work on Ubuntu Hardy (8.04), Lucid 10.04 and Maverick (10.10)

Install Imagemagick and GraphicsMagick

apt-get install imagemagick graphicsmagick

Install Image Magick development files

apt-get install libmagickcore-dev libmagickwand-dev

gem install rmagick

On Hardy:
Install imagemagick from source and after it install development files:

You can read about two popular thumbnail generating methods in this article. The first method requires GD library. If you select the other way you need Imagick which is a native php extension to create and modify images using the ImageMagick API. Let's see the code!