RHCE the next day

1. Achieve password free login

Generate public and private keys

ssh-keygen -t rsa

Copy the public key file to the directory of the server ：
 ssh -copy-id Specify the server

 

  Specify the server

Achieve password free login

Windows Connect to Linux Password free login

  Upload files

  Additional

 

 

2. Settings only allow student1, student2 The user login

 

3.get and post The difference between

 

4.HTTP Status code , What are the commonly used status codes ？

The status code ： It's made up of three figures , The first number defines the category of response , And there are five possible values .

1xx： instructions —— Indicates that the request has been received , To continue processing

2xx： success —— Indicates that the request was received successfully 、 understand 、 Accept

3xx： Redirect —— Further action must be taken to complete the request

4xx： Client error —— The request has a syntax error or the request cannot be implemented

5xx： Server-side error —— The server could not fulfill the legitimate request

Common status code 、 The description of the state is as follows ：

503 Server Unavailable： The server is currently unable to process the client's request , It may return to normal after some time

500 Internal Server Error： An unexpected error occurred on the server

404 Not Found： The requested resource does not exist , for instance ： I typed the wrong one URL

403 Forbidden： The server receives the request , But refused to provide service

401 Unauthorized： Request not authorized , The status code must be equal to WWW-Authenticate Header fields are used together

400 Bad Request： Client request has syntax error , Not understood by the server 200 OK： Client request successful

5.HTTP Request message and response message

http The request message is sent by the request line 、 Request header 、 The blank line and the request message body are composed of several parts ：
http The response message consists of the starting line 、 Response head 、 The blank line and the main body of the response message are composed of ：

6.HTTP How to keep connected

There are two ways to maintain the state ：cookie+session The implementation and token Realization

One .cookie+session Realization

cookie：

       Cookie It's generated by the server side , Send it to the browser , The browser will Cookie Of key/value Save to a text file in a directory , Automatically send this... The next time you request the same website Cookie To server Cookie Can be used in some WEB Persistent state between site sessions

session：

Session It's another mechanism for recording customer status , be based on Cookie Realization , The difference is Cookie Save in the client browser , and Session Save it on the server when the client browser accesses the server , The server records client information in some form on the server , This is it. Session, The client browser only needs to access it from that Session To find the status of the customer .