System Administration

The Book of GNS3
Build Virtual Network Labs Using Cisco, Juniper, and More
By Jason C. Neumann
The Book of IMAP
Building a Mail Server with Courier and Cyrus
By Peer Heinlein and Peer Hartleben
The Book of PF, 3rd Edition
A No-Nonsense Guide to the OpenBSD Firewall
By Peter N. M. Hansteen
Cisco Routers for the Desperate, 2nd Edition
Router and Switch Management, the Easy Way
By Michael W. Lucas
Designing BSD Rootkits
An Introduction to Kernel Hacking
By Joseph Kong
Linux Firewalls
Attack Detection and Response with iptables, psad, and fwsnort
By Michael Rash
Nagios, 2nd Edition
System and Network Monitoring
By Wolfgang Barth
Network Flow Analysis
By Michael W. Lucas
Network Know-How
An Essential Guide for the Accidental Admin
By John Ross
PowerShell for Sysadmins
Workflow Automation Made Easy
By Adam Bertram
Practical Packet Analysis, 3rd Edition
Using Wireshark to Solve Real-World Network Problems
By Chris Sanders
TCP/IP Guide
A Comprehensive, Illustrated Internet Protocols Reference
By Charles M. Kozierok
Wicked Cool Shell Scripts, 2nd Edition
101 Scripts for Linux, OS X, and UNIX Systems
By Dave Taylor and Brandon Perry