Depending on which of the many linux courses that you going to pick and depending on it the tenure varies. The typical length of the course is 4 days, but there are some that take up to 5 days to complete. Ensure that you are thinking about how long you have for the class and which one you want to take.
Picking the right class is going to make your career extremely successful, so choose carefully. You should also make sure that you are aware of what topics will be covered in the class.