If you haven't built a local area network lately, you may have forgotten just how painful a project it can be. But what if your users could just plug in, power on, and connect, building their own ad-hoc network? Zeroconf, the basis of Apple's Rendezvous product and an emerging networking standard, puts the play back into 'plug-and-play.' Here's how Zeroconf works.

Retail systems are a strange lot of machines that include everything from fast food cash registers, to in-store servers, to mainframes. While UNIX, Windows, and DOS have traditionally powered your local department or hardware store, there's more than a handful of companies turning to the Penguin to cash-in on the many benefits of Linux. Cha-ching!

The Apache HTTP server is the most widely-used web server in the world. It's powerful, portable, and extensible. And with the introduction of filters in Apache HTTP 2.0, you'll find even more ways to customize the server to suit your site. Find out how.

As this month's issue of Linux Magazine goes to press, the SCO fear and uncertainty dreadnought continues to strip-mine the landscape of Linux. Each day of the last week brought more SCO allegations and threats. SCO even took Linus' approach to developing the kernel to task, practically calling the massively collaborative model near-willful infringement. But while dung spewed from Utah, IBM shrugged it all off. In fact, Big Blue looks Very Cool Blue so far.

When it comes to running non-Linux software or a second operating system under Linux, many users turn to a commercial solution such as VMWare (http://www. vmware.com), or a full-blown virtual machine, or CodeWeavers' CrossOver (http://www.codeweavers.com/products/ crossover). But the open source world has a lot to offer, too.

While the "P" in "LAMP" most often brings to mind Perl or PHP, the other "P," Python, is no third-wheel. Indeed, with powerful language structures that support objects, dynamic data types, and dynamic typing, and a rich trove of core and contributed programming libraries, the variety of applications that can be built with Python is quite astounding. The Python Users page (found online at http://www.python.org/psa/Users.html) lists just a small sampling: there's a content management system framework (Zope); a Quake level editor (Quake Army Knife, or "Quark"); and an entire web site -- PalmStation.com -- written solely in Python.

Last month's feature, "Personal Post," (available online at http://www.linux-mag.com/2003-07/email_01.html) explained how email is delivered, and also described a variety of power tools ideal for untangling a morass of messages.

One problem faced by administrators of large and small networks alike is performing backups. While backups are simple to perform and a variety of software and hardware is available to help, the logistics of reliably archiving even a handful of machines are quite onerous. Having each user backup his or her own computer seems an obvious solution, but is really quite impractical: equipping each workstation and server with its own backup hardware is prohibitively expensive, and asking users to schedule and run their own backups is tantamount to ignoring the problem altogether.

Monitoring the status of a Beowulf-style cluster can be a daunting task for any system administrator, especially if the cluster consists of more than a dozen nodes. While Linux is extremely stable, hardware problems can cause nodes to crash or become inaccessible, and chasing down problem nodes in a 500-node cluster is painful. Luckily, some sort of statistical resource monitoring can often yield early warnings of impending hardware failures.

When building someone else's software, there's nothing more demoralizing than seeing whole rafts of compiler warnings fly by. A common reaction to such spewage is, "Are these real issues requiring investigation, or is this just the handiwork of a sloppy developer?" Not all warnings indicate problems with code, but there's no way to know for certain without actually looking at each and every warning. Needless to say, when warnings turn out to be nothing, it's downright frustrating -- and a huge waste of time. So, professional developers not only work hard to eliminate compiler warnings, they ask the compiler to produce more of them. Why? There are three very good reasons:

Many large organizations use caching proxy servers to save on network bandwidth utilization (and costs) and improve browsing response times. In fact, an entire industry has grown up around caching proxy appliances. But in the open source world, we've had one of the most advanced proxy servers for many, many years. Squid (http://www.squid-cache.org) is to caching proxy servers as Apache is to web servers -- the hands-down open source winner.

First introduced in 1997, servlets gave developers the ability to write server-side applications in Java. While servlets were great for Common Gateway Interface (CGI) programs and other simple tasks, it soon became evident that producing HTML solely with Java code was cumbersome for all and especially difficult for non-programmers involved in the work.

I admit it. Like anyone else with a decent-speed connection to the Internet, I collect a lot of images. For example, a few months ago, I described a program that looks through Yahoo! news images for pictures of Oregon and some of my favorite singing stars. Sometimes, an image travels multiple paths before it ends up on my disk, and thus gets saved under different names. But that's a waste of disk space, so I want to eliminate duplicates where I can.

One popular method for filtering unsolicited commercial email, or spam, is SpamAssassin (http://www.spamassassin.org). SpamAssassin is a rule-based, mail filtering program that identifies spam. By itself, or combined with Razor (http:// razor.sourceforge.net), a collaborative spam-tracking database, SpamAssassin can effectively eliminate spam from your daily doses of email.