https://www.netutil.app/zh-hans/tags/terminal/ Recent content in Terminal on NetUtil Hugo zh-Hans Sat, 16 May 2026 00:00:00 +0000 https://www.netutil.app/zh-hans/blog/flush-dns-cache-mac/ Sat, 16 May 2026 00:00:00 +0000 https://www.netutil.app/zh-hans/blog/flush-dns-cache-mac/ <p>DNS缓存问题很容易被误诊。您更新了域名记录，等待传播完成，然后打开浏览器，旧网站仍然加载。或者曾经能正常访问的网站突然拒绝连接。服务器没问题，您的网络没问题，问题是您的Mac缓存了一个过时的DNS答案，并且仍然在使用它。</p> <p>刷新DNS缓存会告诉macOS忘记那些存储的答案，重新从头开始查询。只需一条命令，大约五秒钟。</p> <h2 id="为什么mac要缓存dns记录">为什么Mac要缓存DNS记录</h2> <p>每次您访问网站时，Mac都需要将域名（如<code>example.com</code>）转换为IP地址。这个转换过程是这样的：Mac首先检查本地DNS缓存，然后询问DNS解析器（通常是您ISP的服务器或公共解析器如1.1.1.1），如果两者都没有答案，解析器会联系该域名的权威名称服务器。</p> <figure class="blog-svg" role="img" aria-labelledby="dns-flow-title dns-flow-desc"> <svg viewBox="0 0 720 180" xmlns="http://www.w3.org/2000/svg" style="max-width: 100%; height: auto;"> <title id="dns-flow-title">DNS resolution flow on macOS</title> <desc id="dns-flow-desc">A four-step diagram showing DNS resolution: Mac checks local cache, then queries DNS resolver, then resolver contacts authoritative server, then IP address is returned to the Mac.</desc> <style> .dns-label { font-family: -apple-system, system-ui, sans-serif; font-size: 13px; fill: #1d1d1f; text-anchor: middle; } .dns-sublabel { font-family: -apple-system, system-ui, sans-serif; font-size: 11px; fill: #6e6e73; text-anchor: middle; } .dns-box { fill: #F5F5F7; stroke: #D2D2D7; stroke-width: 1.5; } .dns-box-highlight { fill: #E8F4FF; stroke: #007AFF; stroke-width: 1.5; } .dns-arrow { stroke: #8E8E93; stroke-width: 2; fill: none; marker-end: url(#dns-arrow-head); } .dns-return { stroke: #34C759; stroke-width: 1.5; fill: none; stroke-dasharray: 5,3; marker-end: url(#dns-arrow-green); } @media (prefers-color-scheme: dark) { .dns-label { fill: #F5F5F7; } .dns-sublabel { fill: #98989D; } .dns-box { fill: #2C2C2E; stroke: #48484A; } .dns-box-highlight { fill: #1C3A5E; stroke: #0A84FF; } } @media (prefers-reduced-motion: reduce) { .dns-animated { animation: none !important; } } @keyframes fadeIn { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: translateY(0); } } .dns-step1 { animation: fadeIn 0.4s ease-out 0.1s both; } .dns-step2 { animation: fadeIn 0.4s ease-out 0.5s both; } .dns-step3 { animation: fadeIn 0.4s ease-out 0.9s both; } .dns-step4 { animation: fadeIn 0.4s ease-out 1.3s both; } .dns-return-line { animation: fadeIn 0.4s ease-out 1.7s both; } </style> <defs> <marker id="dns-arrow-head" markerWidth="9" markerHeight="7" refX="9" refY="3.5" orient="auto"> <polygon points="0 0, 9 3.5, 0 7" fill="#8E8E93" /> </marker> <marker id="dns-arrow-green" markerWidth="9" markerHeight="7" refX="9" refY="3.5" orient="auto"> <polygon points="0 0, 9 3.5, 0 7" fill="#34C759" /> </marker> </defs> <!-- Box 1: Mac --> <g class="dns-step1"> <rect x="20" y="50" width="120" height="70" rx="10" class="dns-box-highlight" /> <text x="80" y="82" class="dns-label" font-weight="600">Your Mac</text> <text x="80" y="99" class="dns-sublabel">local DNS cache</text> </g> <!-- Arrow 1→2 --> <g class="dns-step2"> <line x1="141" y1="85" x2="189" y2="85" class="dns-arrow" /> </g> <!-- Box 2: DNS Resolver --> <g class="dns-step2"> <rect x="190" y="50" width="140" height="70" rx="10" class="dns-box" /> <text x="260" y="82" class="dns-label" font-weight="600">DNS Resolver</text> <text x="260" y="99" class="dns-sublabel">1.1.1.1 or ISP</text> </g> <!-- Arrow 2→3 --> <g class="dns-step3"> <line x1="331" y1="85" x2="379" y2="85" class="dns-arrow" /> </g> <!-- Box 3: Authoritative NS --> <g class="dns-step3"> <rect x="380" y="50" width="150" height="70" rx="10" class="dns-box" /> <text x="455" y="82" class="dns-label" font-weight="600">Authoritative NS</text> <text x="455" y="99" class="dns-sublabel">holds real records</text> </g> <!-- Arrow 3→4 (IP back) --> <g class="dns-step4"> <line x1="531" y1="85" x2="579" y2="85" class="dns-arrow" /> </g> <!-- Box 4: IP result --> <g class="dns-step4"> <rect x="580" y="50" width="120" height="70" rx="10" class="dns-box" /> <text x="640" y="82" class="dns-label" font-weight="600">IP Address</text> <text x="640" y="99" class="dns-sublabel">returned to Mac</text> </g> <!-- Return path (dashed green) --> <g class="dns-return-line"> <path d="M 640 120 Q 640 155 360 155 Q 80 155 80 121" class="dns-return" /> <text x="360" y="170" class="dns-sublabel" fill="#34C759">cached for future lookups</text> </g> </svg> <figcaption>macOS在本地缓存DNS答案，以便在重复访问时跳过整个查询链。当记录更改时，缓存可能会提供过时的数据。</figcaption> </figure> <p>缓存通常是好事。它能加快浏览速度，因为您的Mac可以跳过最近访问过的网站的整个查询链。问题出现在DNS记录更改时，Mac缓存的答案仍然指向旧目的地。DNS记录上的TTL（存活时间）告诉解析器缓存多长时间，但macOS并不总是精确遵守它。</p>