John R. Levine was a member of a computer club in high school — before high school students, or even high schools, had computers — where he met Theodor H. Nelson, the author of Computer Lib/Dream Machines and the inventor of hypertext, who reminded us that computers should not be taken seriously and that everyone can and should understand and use computers.

John wrote his first program in 1967 on an IBM 1130 (a computer somewhat less powerful than your typical modern digital wristwatch, only more difficult to use). He became an official system administrator of a networked computer running UNIX at Yale in 1975. He began working part-time (for a computer company, of course) in 1977 and has been in and out of the computer and network biz ever since. He got his company on Usenet (the Internet’s worldwide bulletin-board system) early enough that it appears in a 1982 Byte magazine article on a map of Usenet, which then was so small that the map fit on half a page.

Although John used to spend most of his time writing software, now he mostly writes books (including UNIX For Dummies and Privacy For Dummies, both published by Wiley Publishing, Inc.) because it’s more fun and he can do so at home in the tiny village of Trumansburg, New York, where he is the sewer commissioner (Guided tours! Free samples!) and can play with his small daughter when he’s supposed to be writing. John also does a fair amount of public speaking. (Go to www.johnlevine.com to see where he’ll be.) He holds a BA and a PhD in computer science from Yale University, but please don’t hold that against him.

In high school, Margaret Levine Young was in the same computer club as her big brother, John. She stayed in the field throughout college against her better judgment and despite John’s presence as a graduate student in the computer science department. Margy graduated from Yale and went on to become one of the first PC managers in the early 1980s at Columbia Pictures, where she rode the elevator with big stars whose names she wouldn’t dream of dropping here.

Since then, Margy has co-authored more than 25 computer books about the topics of the Internet, UNIX, WordPerfect, Microsoft Access, and (stab from the past) PC-File and Javelin, including Dummies 101: The Internet For Windows 98, UNIX For Dummies, and WordPerfect For Linux For Dummies (all published by Wiley Publishing, Inc.), and Windows XP: The Complete Reference and Internet: The Complete Reference (published by Osborne/McGraw-Hill). She met her future husband, Jordan, in the R.E.S.I.S.T.O.R.S. (that computer club we mentioned). Her other passion is her children, along with music, Unitarian Universalism (www.uua.org), reading, and anything to do with eating. She lives in Vermont (see www.gurus.com/margy for some scenery).

We designed this book to be used when you can’t figure out what to do next. We don’t flatter ourselves that you are interested enough in UNIX to sit down and read the whole thing. When you run into a problem using UNIX (“I thought I typed a command that would copy a file, but it didn’t respond with any message . . .”), just dip into the book long enough to solve your problem.

We have included sections about these kinds of things:

Typing commands

Copying, renaming, or deleting files

Printing files

Finding where your file went

Using the Internet from UNIX

Storing and updating a Web site on a UNIX computer

Connecting and communicating with people on other computers

In this fifth edition, we updated the information about Linux (the popular free version of UNIX), beefed up the information about the new KDE and GNOME window systems, and added information about Internet applications and hosting an Internet site on your own (or someone else’s) UNIX computer.