In my opinion Linux OS is a best choice for newbies to learn embedded system. As It is an open source system,which could help learners gradually master this embedded operation system through many times researches and tests. At the same time, it also is a successful software platform that has been widely applied in many fields.
What about you?
"Embedded system" is a vast field and can't be confined to a single OS. When you say embedded, it could also mean a small assembly code written on an 8-bit controller. It could also mean porting of Linux to a new processor.
So I do not agree that Linux OS is the best choice for newbies to learn embedded system. It all depends on what you want to learn and to what extent...