The relationship between the computer and the kernel, the shell: first, the management of the entire computer hardware is actually the operating system kernel (kernel), the kernel is required to protect, so our average user can only through the shell (shell) to communicate with the kernel, so that the kernel to achieve the work we want. What is a shell? The operating system is actually a group of software, because this group of software in the control of the entire hardware and management system activity monitoring, if this group of software can be arbitrary operation of the user, if the user improper application, will make the whole system to collapse, but we always want to let the user operating system, so there is the application developed on the operating system, These applications allow the user to command the kernel, allowing the kernel to perform the required hardware tasks. The application is at the outermost layer and is therefore called the shell. The Shell's function is simply to provide an interface to the user's operating system, so the shell will be able to invoke other software. Many of the commands used on Linux systems, such as man, chmod, Chown, VI, are all standalone applications, but we can manipulate them through the shell (which is the command-line mode), allowing these applications to invoke the kernel to run the required work. As long as the interface that can manipulate the application becomes the shell. The narrow shell refers to the command-line aspect of the software, including bash and so on. The broader shell includes software for graphical interfaces. The shell types that can be used under Linux can view the/etc/shells file: Some of the services in the system are running, checking the shells that the user is able to use, and these shells queries are used/etc/ Shells this file when the system does not want some users to use a host resource other than a shell, it gives the user some strange resources that will not be able to log on to the host with other services, such as: Laps 1, 3 is root, RICHAPM, Oamonitor account default shell is bash, Circle 2 is a strange resource.
1. Learn about the shell of Bash
