Linux Firewalls
Michael Rash
Quick Start Guide to Penetration Testing
Sagar Rahalkar
Cross-Site Scripting Attacks: Classification, Attack, and Countermeasures
B. B. Gupta and Pooja Chaudhary
SSH Mastery: OpenSSH, PuTTY, Tunnels and Keys
Michael W Lucas
Effective DevOps
Jennifer Davis & Ryn Daniels
sed & awk
Dale Dougherty & Arnold Robbins
Linux iptables Pocket Reference
Gregor N. Purdy