Linux is freely available, and no one is required to register with any central authority, so it is difficult to know. Several businesses survive solely on selling and supporting Linux. Linux news groups are some of the most heavily read on Usenet. Accurate numbers are hard to come by, but the number is almost certainly in the millions.
However, people can register as Linux users at the Linux Counter project, which has been in existence since 1993. In August, 1998, the project counted more than 70,000 users.
Visit the Web site at http://counter.li.org/ and fill in the registration form. If you don't want to use the Web, send E-mail to email@example.com with the subject line, "I use Linux at home," or "I use Linux at work."
The current count is posted monthly to comp.os.linux.misc, and is always available from the Web site.
[Harald Tveit Alvestrand]