Detailed explanation of ssh command under linux

The SSH command in the Linux system environment is a powerful tool for remote connection and security management

Summary: Remote connectivity and security management are mission-critical in modern computing environments. The SSH (Secure
Shell) command, as a secure remote connection protocol, plays an important role in the Linux system. This blog will analyze the past and present, functions, usage, and application scenarios of SSH commands in detail in an easy-to-understand manner, helping readers fully understand and flexibly use SSH commands, and master their application in troubleshooting and security management.

1. The past and present of the SSH command

In the past, remote connections often used non-secure protocols such as Telnet. However, this protocol has security risks because the user's login information and data transmission are all in plain text. The SSH command came into being to provide higher security and confidentiality for remote connections through mechanisms such as encryption and authentication.

2. Function and usage of SSH command

SSH commands are mainly used for remote login and command execution. The following are common usages of SSH commands:

1. Remote login:

ssh [用户名]@[IP地址]

You can remotely log in to the target host through the SSH command. Specify the username and IP address of the target host in the command, and then enter the password for authentication.

2. Specify the port number:

ssh [用户名]@[IP地址] -p [端口号]

If the port number of the SSH server is not the default port 22, you can use the "-p" option to specify the port number.

3. Public key authentication login:

ssh-keygen
ssh-copy-id [用户名]@[IP地址]

Use ssh-keygen to generate a key pair, and use the ssh-copy-id command to copy the public key to the target host to implement public key authentication login and avoid entering a password every time you log in.

4. Execute remote command:

ssh [用户名]@[IP地址] [命令]

SSH commands can be used to execute commands on the remote host without logging in to the interactive terminal of the target host.

5. file transfer:

scp [本地文件路径] [用户名]@[IP地址]:[目标路径]

The scp command can be used to transfer files between local and remote hosts.

3. Application Scenarios of SSH Commands

SSH commands play an important role in the following scenarios:

1. Remote Management:
   SSH commands provide administrators with the ability to remotely manage servers. Through SSH remote login, administrators can perform management operations and configuration changes without direct physical contact with the target host.

2. Troubleshooting:
   SSH commands are very useful in troubleshooting. Administrators can telnet into failed hosts

, and view logs, execute commands, and analyze problems.

3. Secure file transfer:
   Through SCP commands, files can be safely transferred to remote hosts. This is very important for scenarios such as backup, recovery, and file distribution.

4. Cross-network access:
   SSH command can realize cross-network security access. Whether connecting to a remote server across a public network or connecting to an internal network through a tunnel, SSH is a reliable choice.

4. Example code

Here is some sample code that demonstrates how to use SSH commands:

1. Remote login:

ssh [email protected]

This command will log in to the remote host named "example.com" using the SSH protocol, using the username "user" for authentication.

2. Execute remote command:

ssh [email protected] "ls -l"

This command will log in to the remote host and execute the "ls -l" command to return a detailed list of directories.

3. file transfer:

scp file.txt [email protected]:/home/user/

This command transfers the local "file.txt" file to the remote host's "/home/user/" directory.

5. Learn more about SSH commands

If you want to learn more about the functions and usage of SSH commands, you can refer to the following links:

• Official documentation for SSH commands
• Detailed explanation of Linux SSH commands
• OpenSSH official website

Through the reference links, we can learn and understand more features and usages of SSH commands, and further improve our skills and knowledge.

Conclusion:
This blog introduces the SSH command under Linux in detail, including its function, usage, application scenarios and sample code. By using SSH commands, we can implement functions such as secure remote connection, remote command execution and file transfer. As a system administrator and network engineer, proficiency in SSH commands will provide you with better remote management and secure transmission capabilities. At the same time, by understanding the background and history of SSH, we can better understand and appreciate the importance of SSH in ensuring system security.