在当今的网络环境中，Linux系统作为企业级服务器和云计算平台的核心组件，其安全性与稳定性至关重要。Linux防火墙（如iptables、nftables）是保障系统安全的重要工具，合理配置端口开放策略可以有效防止未经授权的访问，提升系统的整体防护能力。
随着云计算和容器化技术的普及，Linux防火墙的使用场景更加广泛，其配置和管理也变得更加复杂。
也是因为这些，了解如何在Linux系统中查询开放端口、排查防火墙规则、优化防火墙配置，已成为系统管理员和开发人员必备的技能。本文将从防火墙的基本原理、端口查询方法、规则管理、安全策略优化等方面，详细阐述Linux防火墙开放端口查询的攻略，帮助读者全面掌握相关技能。 一、Linux防火墙的基本原理 Linux防火墙是用于控制进出系统网络流量的软件，其核心功能是根据预定义的规则，决定是否允许特定的网络连接。常见的Linux防火墙包括： - iptables：这是Linux系统中最常用的防火墙工具，基于包过滤机制，支持动态规则管理。 - nftables：这是Linux 4.14版本之后引入的下一代防火墙工具，性能更优，规则管理更灵活。 iptables和nftables都基于netfilter内核模块，通过链（chain）、表（table）、规则（rule）等结构来管理网络流量。规则通常由源地址、目的地址、端口号、协议类型等条件组成，用于决定是否允许流量通过。 在Linux系统中，防火墙规则通常存储在`/etc/sysconfig/iptables`或`/etc/nftables.conf`文件中，也可以通过`iptables -L`或`nft list ruleset`命令查看当前规则。 二、Linux防火墙开放端口的查询方法 在Linux系统中，查询防火墙开放的端口可以通过以下几种方式实现： 1.使用`iptables`命令查询开放端口 `iptables`是传统防火墙工具，可以通过`iptables -L -n -v`命令查看所有规则，其中包括开放的端口信息。 示例命令： ```bash iptables -L -n -v ``` 输出示例： ``` Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:22 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 ``` 从输出中可以得知，系统允许通过22（SSH）、80（HTTP）端口访问。 2.使用`nftables`命令查询开放端口 nftables是更现代的防火墙工具，其规则管理方式与iptables有所不同，但同样可以通过`nft list ruleset`命令查看所有规则。 示例命令： ```bash nft list ruleset ``` 输出示例： ``` table inet { chain input { type filter hook input priority 0; policy ACCEPT; ct state established,related accept; ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type ipv4/ip6 limit { average 100000 } ct type 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