Linux in the Real World
While computers understand 32-bit IP addresses, you and I don't. My e-mail is email@example.com, not firstname.lastname@example.org (although that works, too). The Domain Name System is the glue that holds together domain names and IP numbers.
You do have an Internet domain name, don't you? You will need one, and once you have it, you will need a Domain Name Server (DNS) in order to use it. DNS setup is fairly straightforward, and I have written a mini-HOWTO on the subject, which will be available from the LDP archives by the time you read this. [FIXME: More information coming here]
DNS places a very light load on a machine, and your DNS server can serve in other capacities, too. Some people put it on their PPP server, some on their news server. We have two: one on our WWW server and the other on a 386-40 dedicated to DNS. To each his own.
E-mail is probably the most useful and the least appreciated aspect of the Internet. Once you have tired of the pretty pictures of the WWW and want to get some work done, e-mail is the tool of choice. Nonetheless, people neglect it too often, at their peril.
If your news server goes down, you will get some gripes, and if your web server goes down, you will get some calls, but if mail goes down, Annie bar the door! Your POP server (the program that lets customers use programs like Eudora to read their mail) usually works out of the box, but your SMTP daemon (such as sendmail) is what does the heavy lifting, and this is where your efforts will be directed.
The NAG includes a good section on mail, and the Mail-HOWTO is also a good starting point. Mail is another of those services with which, once you have it working, your problems are over, but you will spend time getting it working properly. If customers want UUCP, mailbots, or mailing-list support, this means additional work, and you should consider the amount of additional work before knee-jerking into a “Sure, we can do it!” response.
Usenet, the global electronic news system, is distributed mainly over the Internet, although certain UUCP networks and others also offer it. Simply put, any message written by anyone anywhere submitted to public Usenet groups (1000, 4000, 10000—how many are there?) will end up on every Usenet server on the planet. Last I heard, a full Usenet feed (i.e., accepting every group) runs about 400MB per day, so you probably don't want a full Usenet feed coming in over your 56kbps connection.
The News-HOWTO goes over the various options for news servers (programs which accept deliveries, organize the articles, and spit them back out to customers as they request them). Pick one, learn it, and stick with it. At 400MB per day, news is an inherently dangerous thing, kind of like having a water main feeding into your sink, and you can lose control of your news server without a whole lot of effort, filling disks and ruining your day.
News also exacts a heavy toll on the machine that serves it, consuming large amounts of RAM, CPU cycles, and disk space. At the very minimum, you will want your /var/spool/news directory on a separate physical disk. Usually, it is a good idea to have a separate news server, which perhaps also serves as a DNS. Our 486-DX66 groans slightly under a full news feed, and a Pentium might not be a bad choice. Then again, you might not want to run a full news feed, in which case a 486DX-33 might do the trick.
Slackware and most other distributions come with Washington University's wu-ftpd anonymous FTP server built-in, preconfigured, and ready to go. Go to /home/ftp/pub, start throwing stuff in there, and you're off to the races. If your customers want to be able to put up files for FTP on your server, then you might have some work to do.
The WWW, despite all the hype, is not especially difficult to implement, either. Apache, a derivative of NCSA's httpd, is a favorite Linux tool and comes with plenty of neat gizmos. Virtually all web servers are capable of serving information from a public_html directory in a user's home directory, accessible as www.foobar.com/~username/. If you decide to do this, you will want to put your web daemon on the same machine as your users' home directories, which may also be your mail machine. If this, along with PPP, is too much, break out your PPP server and leave mail and web on the one machine. Plus, you can have users access this one central machine via multiple PPP servers (even via multiple remote PPP servers across your greater metro area), instead of having each server duplicate these functions.
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