Apache: The Definitive Guide (3rd Edition)

by Ben Laurie and Peter Laurie

Apache Cookbook

by Ken Coar and Rich Bowen

DNS & BIND (5th Edition)

by Cricket Liu and Paul Albitz.

This book is a must for every system administrator working with DNS. It explains the workings of DNS step by step, staring out with the basic.

DNS & BIND Cookbook (Paperback)

by Cricket Liu

Essential SNMP, Second Edition

by Douglas Mauro and Kevin Schmidt

This is a practical book on SNMP. It starts from the begining with a basic introduction to the SNMP protocol and walk the readers through many of the pitfalls in using SNMP. It covers HP OpenView, but is also using Net-SNMP to show many of the principles. It is therefore useful to anybody who wants to learn more about SNMP, and who does not have access to an commersial tools. It have many good examples and it attempts to answer the readers questions.

HTTP: The Definitive Guide

by David Gourley and Brian Totty

Mastering Algorithms with Perl

by John Macdonald, Jon Orwant, and Jarkko Hietaniemi

Mastering Regular Expressions

by Jeffrey Friedl

Perl Cookbook, Second Edition

by Tom Christiansen (Author), Nathan Torkington

Postfix: The Definitive Guide

by Kyle Dent

After using Sendmail for many, many years, I took Postfix out for trial run, and have not looked back ever since. If you are still running sendmail, you would be well serverd by checking out Postfix, and this is the book to do it with.

sendmail Cookbook

by Craig Hunt

sendmail, 3rd Edition

by Bryan Costales and Eric Allman

TCP/IP Illustrated, Volume 1 — The Protocols

by W. Richard Stevens

TCP/IP Illustrated, Volume 2 — The Implementation

by Gary R. Wright and W. Richard Stevens

TCP/IP Illustrated, Volume 3 — TCP for Transactions, HTTP, NNTP, and the UNIX® Domain Protocols

by W. Richard Stevens

TCP/IP Network Administration (3rd Edition)

by Craig Hunt

Linux Administration Handbook (2nd Edition)

by Evi Nemeth, Garth Snyder, Trent R. Hein

This book is by the same authors as the one above, but is specific to Linux. The comments from above goes for this book too

UNIX System Administration Handbook (3rd Edition)

by Evi Nemeth, Garth Snyder, Scott Seebass, and Trent R. Hein

This book is a clasic. Since the first edition in 1989, this book have covered nearly every aspect of Unix System Administration. As none of us knows everything, this is a handy reference book, even in these days of Internet and search—engines galore.