You can think that these manufacturers provide a new interface; you can also think that these manufacturers provide a middleware.

To put it simply, the level you can operate is not actually Linux, but an operation layer, such as the graphical interface of a web page. If the manufacturer is lazy enough or pursues high efficiency enough, it will not have this graphical interface for a long time and will instead give you a command line interface.

Clicking on the graphical interface actually executes a middleware script on the web page. This script is what really works. It will change the content under the Linux system, such as IP and routing.
If there is no graphical interface, then you execute cmd -A -B -C on the command line interface. This command line interface actually still calls the middleware.
For example, display interface e0/0 may actually execute ifconfig eth0; ethtool eth0; and then integrate the data and output it to you.

My previous company also did something similar. You can take a look: vyatta.

Cisco IOS: https://learningnetwork.cisco.com/thread/47297
Huawei VRP was not found - -In fact, there is not much information about Huawei VRP on the Internet,

The most important system program provided to users by the Linux system is the Shell command language interpreter. It doesn't

It belongs to the kernel part, but runs outside the core in user mode. Its basic function is to explain and

Execute various commands entered by the user to realize the interface between the user and the Linux core. After the system is initially started, kernel

Create a process for each end user to execute the Shell interpreter. Its execution process is basically

Follow the following steps: (1) Read the command line entered by the user from the keyboard. (2) Analyze the command with command

name is used as the file name, and other parameters are transformed into the

Form. (3) The terminal process calls fork() to create a child process. (4) The terminal process itself uses the system

The system calls wait4() to wait for the child process to complete (if it is a background command, it does not wait). Dangzijin

calls execve() when the process is running, and the child process searches the directory for

Close the file (this is the file composed of the command interpreter program), transfer it into the memory, and execute the program (

Explain this command). (5) If there is an ampersand (background command symbol) at the end of the command, the terminal process

There is no need to wait for the system call wait4(), a prompt will be sent immediately, allowing the user to enter the next command, go to ⑴

. If there is no ampersand at the end of the command, the terminal process will have to wait until the child process (that is, run the command

) terminates after completing the processing and reports to the parent process (terminal process). At this time, the terminal process wakes up

, after doing necessary judgment and other work, the terminal process sends a prompt to let the user enter a new command, and then restart

Repeat the above process.

http://www.cnblogs.com/wuyuegb2312/p/3399566.html