Introduction to Virtual Machines (eight)--unix virtual machine model

Unix
UNIX Virtual machine model



The concept of using and designing virtual machines is an effective way to build interactive, robust virtual devices. This method can be used to solve many problems faced by computer engineers. In Unix operating systems, the concept and process model of virtual machines are highly unified. The UNIX operating system is one of the most successful and respected operating systems used by modern computers. The widespread use of Unix enabled his virtual machine features to be fully exploited and categorized as real virtual machines. The UNIX operating system uses a series of standalone processes to complete the user's instructions. UNIX can schedule and configure the processes it creates to pass and manipulate data. Conceptually, a UNIX process can be viewed as a virtual machine because it has many of the characteristics of the virtual machine, which are the organic components of the other three virtual machine models. UNIX virtual machines acquire features similar to the IBM virtual machine model by using a consistent user shell (user shell), which completes similar actions to the virtual machines of IBM virtual machine systems. The UNIX user shell can be considered a stand-alone virtual machine, because each user interface is a separate entity with a complete set of hardware resources. The user shell is like a skilled dispatcher, which generates new processes and directs data from one process to another to complete the user's command to submit to the user's shell. The enclosure is limited by memory limits and some shared resource coordinate boundaries, which prevents collisions of critical hardware devices. However, the user shell still retains the principle of independence and segmentation in the IBM model.









The UNIX process also features a Java virtual machine because it leverages the unified Platform library functions provided by the hierarchical design of the operating system. The UNIX operating system provides a unified collection of different library service programs for the user process in progress. The UNIX operating system is layered design, with each layer providing services and functions to its upper layer. This standardized design allows users to use a standard set of functions to execute their programs on different platforms. This is possible on UNIX using the POSIX standard. This standard is provided by the IEEE POSIX project team in the information technology Portable Operating System interface (POSIX????). Part II: Shell and Function Program) "published, it sets the Unix shell and application routines standards." Although the code for a particular program still needs to be recompiled on each platform, the program code is truly portable, because each UNIX platform that obeys the standard supports the same set of functions.







In the underlying structure of the UNIX operating system, the user shell also embodies some of the features of the OSI virtual machine model. The extension of the UNIX operating system to hardware is one of the basic features of UNIX. For example, the hardware might use a single disk array to provide a large file system. These standalone disks are a disk for the user, and the instruction layer passes the user-layer command to the hardware or returns the hardware instructions to the user layer.







The UNIX virtual machine model integrates the characteristics of all the above three virtual machine models, generating a very reliable and common approach-creating other processes and passing process output to accomplish user tasks. In this way, a UNIX process can work like a virtual machine. The UNIX user process obtains user input and then creates a series of virtual machines. The output of each virtual machine will be the input of the next virtual machine.






The end result of data manipulation and output redirection is the completion of user-specified tasks.