What is the use of linux ssh?

Ssh is used to remotely log in to the Linux server to manage and maintain the system. SSH is a protocol designed to provide security for remote login sessions and other network services; using the ssh service (referring to software that implements the SSH protocol), you can remotely log in to the server to manage and maintain the system, preventing information leakage during remote management.

#The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

1 What is ssh in linux? What is the use?

(1) ssh is a protocol

SSH (Secure Shell) is more reliable and designed for remote login sessions and Other network services provide security protocols, and the use of the SSH protocol can effectively prevent information leakage during remote management.

(2) ssh service

Linux is generally used as a server. We usually use the ssh service (referring to the software that implements the SSH protocol) to log in remotely. Go to the Linux server to manage and maintain the system.

• OpenSSH is a free and open source implementation of the SSH (Secure SHell) protocol.
• OpenSSH server: sshd (Linux server starts the service)
• OpenSSH client: ssh (client starts, access the server through it)

2 What is the key-based security verification process of ssh?

You need to create a pair of keys and put the public key on the server. When connecting to the SSH server, the client sends a request to the server and uses your public key for security verification. After the server receives the request, it first searches for your public key in your home directory on the server, and then compares it with yours. The public key sent is compared. If the two keys match, the server encrypts the "challenge" with the public key and sends it to the client software. After the client software receives the "challenge", it can decrypt it with your private key.

3 What is the difference between symmetric encryption and asymmetric encryption?

(1) Symmetric encryption

The same key (secret) is used for encryption and decryption key). Highly efficient, a major drawback of symmetric encryption is the management and distribution of keys. During the process of sending keys, there is a great risk that the keys will be intercepted by hackers. The common practice in reality is to asymmetrically encrypt the symmetric encryption key and then transmit it to the person who needs it.

(2) Asymmetric encryption

Asymmetric encryption provides a very secure method for data encryption and decryption. It uses A pair of keys, public key and private key. The private key can only be kept securely by one party and cannot be leaked, while the public key can be sent to anyone who requests it. Asymmetric encryption uses one of the keys in the pair for encryption, while decryption requires the other key. Currently the most commonly used asymmetric encryption algorithm is the RSA algorithm. Although asymmetric encryption is very secure, it is very slow compared to symmetric encryption, so we still have to use symmetric encryption to transmit messages, but the key used in symmetric encryption can be sent out through asymmetric encryption.

4 The role of asymmetric encryption RSA algorithm

(1) Encryption: public key encryption private key decryption

Mainly used to encrypt data to prevent it from being illegally obtained by others to ensure data security. The data is encrypted using the public key, and only the private key can decrypt it. Even if the ciphertext is obtained by a third party on the Internet, it cannot be decrypted without the private key, thus ensuring data security.

1. A generates an RSA key file on his computer, a private key file and a public key file, and sends his public key to B.
2. At this time, B wants to send information to A, so B uses A's public key to encrypt his message and then sends it to A. (The ciphertext transmitted on the network cannot be decrypted without A's private key, and it will be useless after others obtain it)
3. A uses his private key to decrypt B's message.

(2) Authentication: Private key encryption and public key decryption

is mainly used for identity verification to determine the authenticity of a certain identity sex. After encrypting with the private key, decrypt it with the corresponding public key to verify the authenticity of the identity.
SSH public key login uses the second function.

5 How to generate ssh key pair?

• After running the above command, a pair of public and private keys will be generated, which will be saved in id_rsa, id_rsa.pub under ~/.ssh/ by default.
• id_rsa is the private key and id_rsa.pub is the public key. The private key must be kept properly.
• The permissions of id_rsa must be 600, chmod 600 ~/.ssh/id_rsa. 600 means (-rw------) only the owner has read and write permissions.

6 ssh configuration config file and quick login

(1) Quick login configuration

You can define some shortcut key login configurations under ~/.ssh/. The configuration is in ~/.ssh/config

config structure is as follows:

Host kafka_broker_01                      #定义主机别名
ServerAliveInterval 30
HostName 122.22.222.102                   #主机ip
Port 33033                                #ssh 端口
User bila                                 #用户名
IdentityFile /Users/bila/.ssh/id_rsa      #私钥
ProxyCommand ssh w_x_bastion -C -W %h:%p  #设置跳板机

(2) Login

Specify user login

ssh bila@192.168.0.103

Specify port number login

ssh ssh 192.168.0.103 -p 2022

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