Linux in a Nutshell, Fifth Edition

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Chapter 2: System and Network Administration Overview

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

It is possible to make it through a chain without matching any rules that have a

target. If no rule matches the packet in a user-defined chain, control returns to the

chain from which it was called, and the next rule in that chain is checked. If no

rule matches the packet in a built-in chain, a default policy for that chain is used.

The default policy can be any of the special targets that determine what is done

with a packet. The valid targets are detailed in Chapter 3.

You use the iptables command to define the rules. Once you have the rules

defined you can use iptables-save to create a file with all the rule definitions, and

iptables-restore to restore those definitions when you reboot.

For more information on the kinds of decisions you need to make and the consid-

erations that go into defining the rules, see a general book on firewalls such as

Building Internet Firewalls (O’Reilly). For more details on iptables, consult the

Linux Network Administrator’s Guide (O’Reilly), Linux iptables Pocket Reference

(O’Reilly), or one of the relevant HOWTOs, such as the “Packet Filtering

HOWTO.” These HOWTOs and a number of tutorials are available on the

Netfilter web site at http://www.netfilter.org/.

Overview of NFS

The Network File System ...