Linux is generally composed of four main parts: kernel, shell, file structure and utilities. The kernel is the most fundamental and important of all the components.
1. linux kernel
The kernel is the core of the entire operating system and manages the hardware and software resources of the entire computer. The kernel controls the operation of the entire computer, provides corresponding hardware drivers, network interface programs, and manages the execution of all programs. The kernel provides the most basic functions of the operating system.
The Linux kernel source code is mainly written in C language. The Linux kernel adopts a relatively modular structure. The main modules include storage management, process management, file system management, device management and drivers, network communication and system calls.
The Linux kernel source code is usually installed in the /usr/src/linux directory for users to view and modify.
2.linux shell
The shell is the user interface of the system, providing an interface for users to interact with the kernel. It receives commands entered by the user and sends them to the kernel for execution. Essentially, the shell is a command interpreter that interprets commands entered by the user and sends them to the kernel. The shell also has its own programming language for command editing, which allows users to write programs consisting of shell commands. The shell programming language has many characteristics of ordinary programming languages, such as it also has loop structure and branch control structure, etc. The shell program written in this programming language has the same effect as other applications.
3.linux file structure
The file structure is an organization method for files stored on storage devices such as disks, and is mainly reflected in the organization of files and directories. Directories provide a convenient and efficient way to manage files. We can switch from one directory to another, and we can set permissions on directories and files, and set the level of file sharing.
With linux, users can set permissions on directories and files in order to allow or deny others access to them. The linux directory adopts a multi-level tree structure. Users can browse the entire system, enter any authorized directory, and access the files there.
4. linux utilities
Standard linux systems have a set of programs called utilities, which are specialized programs, such as editors, that perform standard computing operations, etc. Users can also generate their own tools. Utilities can be divided into 3 categories.
(1) Editor: Used to edit files. The editors of linux mainly include Ed, Ex, Vi and Emacs. Ed and Ex are line editors, Vi and Emacs are full screen editors.
(2) Filter: used to receive data and filter data. A linux filter (Filter) reads input from user files or elsewhere, examines and processes the data, and ends the output.
(3) Interactive programs: allow users to send information or receive information from other users. The interactive program is the information interface between the user and the machine.