Offensive Shellcode from Scratch
Rishalin Pillay
Linux Firewalls
Michael Rash
Linux Advanced Routing and Traffic Control HOWTO
Gregory Maxwell & Remco Mook & Martijn Oosterhout & Paul Schroeder & Jasper Spaans & Bert Hubert
SSH Mastery: OpenSSH, PuTTY, Tunnels and Keys
Michael W Lucas
Cyber Security and Network Security
Sabyasachi Pramanik & Debabrata Samanta & M. Vinay & Abhijit Guha
GitHub For Dummies
Sarah Guthals & Phil Haack
Linux Bible (10th edition)
Christopher Negus