Best practices guide for SSH in Linux SysOps

Best Practice Guide for SSH in Linux SysOps

Introduction:
In today's information technology field, the Linux system is an irreplaceable and important operating system one. With the popularity of cloud computing and virtualization technology, the use of Linux systems has gradually been widely promoted. SSH (Secure Shell), as a standard tool for remote management of Linux systems, also plays a vital role. This article will introduce the best practice guide for SSH in Linux SysOps and provide specific code examples to help SysOps manage Linux systems more securely and efficiently when using SSH.

1. Basic knowledge of SSH
SSH is a protocol for remote login and command execution through encrypted communication. It provides secure transmission and control terminal functions, greatly facilitating remote management operations. Before understanding the best practices of SSH, let's review the basic knowledge of SSH.

1. How SSH works
   SSH achieves secure communication by establishing an encrypted tunnel between the client and the remote server. Before establishing a connection, the client and server will perform identity authentication to ensure the security of both parties communicating. SSH uses asymmetric encryption technology to complete identity authentication and key exchange, and uses symmetric encryption technology to ensure the confidentiality of the communication process.

2. Basic components of SSH
   After understanding how SSH works, we need to understand some basic components related to SSH:

   (1) SSH client: used A tool to connect to a remote server and perform remote management operations.

   (2) SSH server: A service installed on the remote server and used to accept connections from SSH clients and perform specified operations.

   (3) SSH key pair: Key pair used for identity authentication, including public key and private key. The private key is usually kept on the client, while the public key is stored on the remote server.

2. SSH Best Practice Guide
After understanding the basic knowledge of SSH, we will now introduce some best practice guides for using SSH in Linux SysOps and provide Specific code examples.

1. Use SSH key pair for identity authentication
   In actual operation, using SSH key pair for identity authentication is a more secure and efficient way. The following are the steps to use SSH key pair for authentication:

(1) Generate SSH key pair
Use the following command on the local client to generate an SSH key pair:

ssh-keygen

This command will generate a default key pair and save the private key in the ~/.ssh/id_rsa file and the public key in the ~/.ssh/id_rsa.pub file.

(2) Copy the public key to the remote server
Use the following command to copy the public key to the authorized_keys file of the remote server:

ssh-copy-id user@remote_host

This command will copy the local public key to in the authorized_keys file of the remote server to achieve password-free login.

2. Disable SSH root login
   In order to enhance the security of SSH, it is a common practice to disable the root user's SSH login. Disabling SSH logins for the root user prevents potential attackers from brute force password cracking to log into the server. The following are the steps to disable root login:

(1) Open the SSH service configuration file
Edit the SSH service configuration file /etc/ssh/sshd_config:

sudo vi /etc/ssh/sshd_config

(2 ) Find the following line and change it to no

PermitRootLogin yes

Change to:

PermitRootLogin no

(3) Save and exit the configuration file
Save and exit the configuration file, and restart the SSH service:

sudo service sshd restart

3. Use a strong password and SSH key pair for two-factor authentication
   To further enhance the security of SSH, you can use a strong password and an SSH key pair for two-factor authentication. This two-factor authentication method can greatly improve the protection of the server. The following are the steps for two-factor authentication using a strong password and SSH key pair:

(1) Encrypt the key with a password
Use the following command to encrypt and protect the generated private key:

ssh-keygen -p -f ~/.ssh/id_rsa

This command will ask you to enter a password to encrypt the private key.

(2) Configure SSH server
Edit the configuration file /etc/ssh/sshd_config of the SSH service and change the following line to yes:

PasswordAuthentication yes

(3) Save and exit the configuration File
Save and exit the configuration file, and restart the SSH service:

sudo service sshd restart

With the above configuration, the user can successfully log in only if both the correct password and the correct key are provided.

Conclusion:
This article introduces best practice guidelines for using SSH in Linux SysOps and provides specific code examples. By following these best practices, SysOps can manage Linux systems more securely and efficiently, and provide basic guarantees for system security. I hope this article will be helpful to SysOps when using SSH and can improve its work efficiency and security.

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