Linux is a UNIX-like system. Many people think that Linux and UNIX are very similar, and some people even think that Linux is UNIX. In fact, the difference between the two is still very big. First of all, Linux is open source, free and available. Use, and UNIX is not open source; secondly, Linux has good cross-platform features, but UNIX cross-platform performance is very weak, and most of them need to be used with hardware. Personally, I have much more exposure to Linux than UNIX in my working environment, so I have almost no knowledge of UNIX.
The core of Linux is the kernel. The existence of the kernel is to control the hardware and software on the computer system, that is, to allocate the hardware and execute the software when needed. Specific performance: application management, file system management, system memory management, and hardware equipment Management. The concept of "kernel" is mentioned here. The kernel is one of the components of Linux. Other components of Linux include shell, GUI, system utilities and applications. Let's take a look at the architecture of Linux to deepen our understanding:
From the figure we can see that Linux is mainly divided into two parts, one of which is user space, which mainly includes applications and C libraries, and the other part is kernel space. This part is mainly Including system call interface, kernel and platform structure related code. Have you considered why this is divided into two parts? Because Linux is from the perspective of the CPU, in order to protect the security of the kernel, the system is deliberately divided into two parts. The second is that modern CPUs implement different working modes. In different modes, the CPU can execute instructions and access registers differently. The Linux kernel is indispensable in the system startup process, and the kernel needs to be guided during the startup process. There is also a feature that must be explained by Linux, that is, everything is a file , even hardware devices are regarded as files, called device files, so access to hardware devices can be achieved by reading and writing device files.
I’ll stop here today about the text, and continue tomorrow.
**Extension:** 1. The communication method between processes used by
Linux 2. The default operating level of the Linux system
