An article written by Avishek Kumar, published in tecmint magazine gives a brief overview of rbash - a restricted bash shell for GNU/Linux and Unix systems along with some relevant examples.
Linux Shell is one of the most fascinating and powerful GNU/Linux powered tool. All the application, including X, is built over shell and Linux shell is so powerful that the whole Linux system can be controlled precisely, using it. The other aspect of Linux shell is that, it can be potentially harmful, when you executed a system command, without knowing its consequence or unknowingly.The Restricted Shell is a Linux Shell that restrict some of the features of bash shell, and is very clear from the name. The restriction is well implemented for the command as well as script running in restricted shell. It provides an additional layer for security to bash shell in Linux.