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.
Read MoreIntroduction to Shell Scripting: Automating Tasks on Linux Servers
Shell scripts are automated execution tools in Linux that write commands into a text file in sequence to replace repetitive manual operations and improve efficiency. They are essential skills for server management. Their basic syntax includes variable assignment (no spaces around the equals sign), conditional judgment (if-else), and loops (for/while). The first "Hello World" script requires defining variables, adding execution permissions (chmod +x), and running the script. Practical scripts, such as disk monitoring, extract the root partition usage rate using commands like `df -h` and trigger an alert when it exceeds 80%. Precautions: Execute permission must be granted before running, no spaces in variable assignment, and use `./` to specify the current directory when executing. Learning can start with basic exercises, and after mastering variables, conditions, and loops, one can advance to learning `crontab` for scheduled tasks to achieve automated operations and maintenance.
Read MoreFTP Service Setup: A Guide to File Transfer on Linux Servers
This article introduces the method of setting up an vsftpd FTP server on Linux systems. FTP is a standard protocol for network file transfer, and vsftpd has become a popular choice for Linux due to its security and stability. The steps include: 1. Preparation: A Linux server (e.g., CentOS/Ubuntu), administrator privileges, and network configuration are required. 2. Installation: For CentOS, use `sudo yum install vsftpd -y`, and for Ubuntu, use `sudo apt install vsftpd -y`. 3. Start the service and set it to start on boot: `systemctl start/ enable vsftpd`. 4. Firewall configuration: Open port 21 (control connection) and passive ports 50000-60000 (data transfer). 5. Create FTP users: Root login is prohibited. Use `useradd` to set the home directory, and `chown`/`chmod` to modify permissions. 6. Configure vsftpd.conf: Enable local user login and write permissions, restrict users to their own home directories, and specify the passive port range. 7. Testing: Connect locally using `ftp localhost`, or remotely with tools like FileZilla. Common issues such as connection timeouts and permission errors require checking the firewall, service status, and directory permissions. The above steps can complete the basic setup.
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