Detailed Explanation of Linux Network Services: From DNS to FTP

This article introduces the basic content of Linux network services, with a focus on DNS and FTP services. Linux network services are core programs that provide network functions (such as domain name resolution and file transfer) for servers, helping to understand network communication logic and manage server maintenance. DNS (Domain Name System), as a "translator", converts domain names (e.g., www.baidu.com) into IP addresses. Its working principle includes local cache queries and recursive/iterative queries to DNS servers (e.g., 114.114.114.114). The Linux configuration file is /etc/resolv.conf, which records DNS server addresses. FTP (File Transfer Protocol), as a "courier", uses the control connection (port 21) to transmit instructions and data connections (port 20 or random ports) to transfer files. vsftpd is commonly used in Linux, and the configuration file vsftpd.conf controls anonymous or user permissions. Common issues: For DNS, check resolv.conf and use nslookup. For FTP, verify the status of vsftpd and the port (21). It is recommended to practice nslookup to test domain name resolution or anonymously connect to public FTP servers to enhance network service management capabilities.