Chapter 11. Setting Up Network Services

Linux's greatest strength is its powerful and robust networking capabilities. The good news is that everything about Linux's networking setup is open to inspection and completely configurable. Nothing is hidden from the user, and no parameters are forced on you. The challenge is to get the most out of this setup.

Basic networking principles don't differ much between Windows and Linux, and indeed the principles aren't unfamiliar. This chapter begins with an overview of networking and then looks in more detail at Linux networking on a local area network (LAN) and the Intertnet.

This chapter explains how to set up a LAN that includes a Linux Samba server, which lets Microsoft Windows and Unix systems access shared files and printers across the network. Samba not only lets you share files and printers, it can also be used to back up and restore files via the network.

This chapter also explains how to set up and configure the Apache web server and an SSH server, which you can use to remotely administer your system. These applications let you and others access data on your Linux system via the Internet. These applications will be most useful if your system is connected to the Internet 24/7. But, even if your connection is intermittent, you and others can access the services these applications provide whenever the connection is active.

Finally, the chapter also explains how to implement a basic host firewall to help protect your systems from unauthorized access via the Internet. Security is best when it consists of multiple layers. So, you're strongly urged not to connect any host to the Internet except through a network firewall. To help you ensure that your host and network firewalls are working, the chapter explains how to use Nmap to test your security.

If your host is protected?as it should be?by a host or network firewall, hosts on the other side or the firewall will not be able to connect to services offered by your host. To permit such hosts to access services, you must disable or customize the network and host firewalls. Ask your network firewall administrator to enable access to your host's services. Also, you must disable your host firewall, as described inSection 11.5.2. However, you should disable the firewall only if your host resides on a trusted LAN that is protected from access by Internet hosts and other untrusted hosts.

Previous editions of this book provided instructions on setting up a DHCP server that enables you to manage network configurations centrally. However, Red Hat Enterprise Linux WS does not provide a DHCP server. If you need a DHCP server for your LAN, you may find it convenient to purchase a gateway router of the sort described in Chapter 10. Many gateway routers provide a simple DHCP server adequate for use on home and small business LANs.

Most Internet services are configurable only by the root user. So, most of the operations in this chapter require that you be logged in as root, or possess temporary root privileges as indicated by the keys icon.