说明：  Linux学习核心知识，有助于平时Linux的学习，加深知识的理解，提示一些可能学习时忽略的关键点，让你能更加全面的了解Linux
(Learning the core knowledge of Linux is helpful to the study of Linux at ordinary times, deepen the understanding of knowledge, prompt some key points that may be ignored in learning, so that you can have a more comprehensive understanding of Linux)