Basically, if you're a complete Linux newbie and looking for a quick and easy guide to get you started this is it.
The Ubuntu Karmic Koala Bible is a guide that's both great for Linux initiates, and invariably useful for Linux intermediates.
Contains technology strategy articles, sample code, tips, Oracle and partner news, how to articles for developers and DBAs, and more.
The topics covered in this 500+ page eBook include Linux network, Linux kernel, security, configuration, tuning and optimization. A must read for any serious Linux user.