As the popularity of the Linux operating system grows, the need for Linux training also will increase -- to the tune of $311 million in the United States by 2004, according to IT research firm IDC, Framingham, Mass. "The rapid adoption of Linux into corporations and the increasing deployment of Linux servers on mission-critical applications is sparking demand for training," says Michael Brennan, a senior analyst with IDC's IT Education and Training Services research program. "As the population of Linux users increases, the opportunity for training will rise significantly, and new players will come to the field." Providing Linux training is no easy task, however. Because it is an open-source operating environment, Linux is constantly being updated. The training has to keep pace with the updates, and it has to address the diverse requirements of the different types of users. "Vendors wishing to capture a share of the Linux training market will have to offer e-learning programs, develop flexible content, participate in educating high-tech and IT recruiters, and be aware of local Linux training needs," says Anne-Sophie Dankens, an analyst with IDC's IT Education and Training Services research program.