Presenting on the topic 'Linux' is as broad as presenting on the topic 'Color'. It is much easier to present on the color blue, or the color red, or a particular shade of either of those. There are also composite colors, primary colors, secondary colors (both additive and subtractive), and so on. The same problem exists the the general topic 'Linux'.
Do you have a more specific focus? What idea, concept, or functionality are you trying to present ultimately?