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Chapter 9
Linux and the Internet

This chapter covers:

  Linux and the Internet
  SLIP and PPP
  Electronic mail
  The World Wide Web
  Web browsers
  The UUCP commands
  Using FTP
  The telnet command
  Using the Usenet

Getting on the Worldwide Network

The Internet has been the recipient of a ton of hype recently, and with good reason: it’s one of the most exciting developments in the computer world in quite some time. As both a computer user and a Linux user, you’ll greatly benefit from the many possibilities offered by the many offerings of the Internet.

As a matter of fact, you’ve probably noticed the many references to the Internet throughout the course of this book. It seems as though anyone who wants to do any advanced work with Linux needs a link to the Internet. (As did the authors of this book, who spent much of their time planning this book and coordinating material through electronic mail and the Internet.) Usenet newsgroups—which we cover in Appendix A—as well as great Web sites can certainly enhance your understanding and usage of the Linux operating system.

How you connect to the Internet depends on your specific circumstances, however. If you’re using Linux in a corporation that’s already connected to the Internet, you can merely piggyback from that connection. If you’re working on a stand alone Linux workstation, you can set up your own Internet connection with the aid of an Internet service provider.

Both of these possibilities exist because of Linux’s built-in networking capabilities—namely, TCP/IP, which you learned about in Chapter 8. Basically, this support for TCP/IP allows a Linux user to use another computer on the network. In Chapter 8, the computers on the network were in the same physical location as your computer. On the Internet, the computers on the network can be just about anywhere. (In other words, the Internet is basically the world’s largest TCP/IP network.)

The concept behind TCP/IP networking is actually pretty simple. Each machine on the network has an individual TCP/IP address, and every other machine on the network can access this machine (if only to be denied access, of course; there are some security measures involved if need be). The extent of the network depends on your needs; some companies purposely restrict their TCP/IP networks to a very confined set of machines; other allow full access to the global Internet.

In this chapter, we’ll discuss getting on the Internet using the tools built into Linux.

Finding a Window to the Internet

If you aren’t connected to the Internet via a direct network connection, you’ll need to make arrangements to do so. There are two ways to do this.

One method involves piggybacking off of a machine that is directly connected to the Internet. In this manner, you can essentially use the specifics of the connected machine. Connectivity tools that fall under this category include SLiRP, which is run in a remote UNIX shell account and makes it act like a SLIP/CSLIP account. We compiled it on an Ultrix machine and connected to it with DIP. It works great! The source for it is on the CD-ROM in /contrib.


NOTE:  The term program, which was covered in the first edition of this book, is no longer supported under newer versions of Linux.

Linux’s SLIP and PPP Tools

If you don’t have a permanent TCP/IP connection to the Internet through work or a friend, you can use Linux’s SLIP and PPP tools to connect to the Internet via an Internet service provider of some sort. SLIP (Serial Line Internet Protocol) and PPP (Point-to-Point Protocol) allow you to connect to another TCP/IP machine.

To connect to the Internet via SLIP and PPP, your implementation of Linux must first support both protocols. If you installed directly from the CD-ROM, your Linux kernel will indeed support SLIP and PPP; if you look at the screen closely when you boot Linux, you’ll notice that SLIP and PPP will be listed. However, if for some reason you decided to compile your own kernel, then you should have had the foresight to compile in SLIP and PPP support. (You were asked if you wanted support for these protocols as part of the make process.) If not, then you’ll need to go back and compile a new kernel, paying special attention to the Network section of the makefile.

After doing that, you’ll set up an account with a service provider (like Netcom, PSI, GNN, Microsoft Network, or Minnesota Regional Network), which gives you Internet access using a standard modem. When you connect via a service provider, you’ll be assigned an IP address right on the spot; the process yields a dynamically assigned IP address, which is then used by your Linux system to connect to the Internet.

When you set up an account, you should get a list of information from the service provider. Out of this information, you’ll need to know the following:

  The access telephone number—if you don’t have this number, you can’t dial up the service provider.
  The IP numbers of the Domain Name Servers. These are the servers your system looks to when you want to connect to another machine on the Internet. Without these servers, your Linux system would be lost in cyberspace.
  Your username and password.
  The mechanism for logging on the system. This is a little more daunting than it looks, because it seems that every service provider handles dialup connections a little differently. As an example: our service provider uses a standard UNIX-style login procedure, where the entry of a username and a password is followed by a standard UNIX prompt:

  Welcome to the Twin Cities MRNet dialIP Service.

  User Access Verification

  Username:

  Password:

  slip-server> ppp


After entering ppp at the command prompt, the server initiates the PPP protocol with your machine. This is not standard in the ISP world; most initiate the process immediately after you enter your password.

Basically, SLIP and PPP do the same thing. However, SLIP (the older of the two protocols) is decreasing in popularity, because PPP (quite honestly) is easier to configure and use. Linux contains the dip command, which handles SLIP connections to a service provider.


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