CyBOK
Awais Rashid & Howard Chivers & George Danezis & Emil Lupu & Andrew Martin
The Wireshark Field Guide
Robert Shimonski
How Linux Works, 3rd Edition
Brian Ward
Linux Advanced Routing and Traffic Control HOWTO
Gregory Maxwell & Remco Mook & Martijn Oosterhout & Paul Schroeder & Jasper Spaans & Bert Hubert
Bash Idioms: Write Powerful, Flexible, Readable Shell Scripts
Carl Albing & J P Vossen