"If you're even thinking of doing any security engineering, you need to read this book" โ bruce schneier
open source as business strategy. ron goldman, richard p. gabriel.
linux kernel internals for enthusiasts (yr. 1999 / kernel 2.0.33)
"Ruby Grundlagen โ PDF zum Buch 'RapidWeb Development mit Ruby on Rails'"
free freebsd book by greg 'grog' lehey.