Files
rancher-docs/troubleshooting/other-troubleshooting-tips/dns.html
T

26 lines
55 KiB
HTML
Raw Blame History

This file contains invisible Unicode characters
This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.
<!doctype html>
<html lang="en" dir="ltr" class="docs-wrapper docs-doc-page docs-version-current plugin-docs plugin-id-default docs-doc-id-troubleshooting/other-troubleshooting-tips/dns">
<head>
<meta charset="UTF-8">
<meta name="generator" content="Docusaurus v2.3.1">
<title data-rh="true">DNS | Rancher</title><meta data-rh="true" name="viewport" content="width=device-width,initial-scale=1"><meta data-rh="true" name="twitter:card" content="summary_large_image"><meta data-rh="true" property="og:url" content="https://ranchermanager.docs.rancher.com/troubleshooting/other-troubleshooting-tips/dns"><meta data-rh="true" name="docusaurus_locale" content="en"><meta data-rh="true" name="docsearch:language" content="en"><meta data-rh="true" name="docusaurus_version" content="current"><meta data-rh="true" name="docusaurus_tag" content="docs-default-current"><meta data-rh="true" name="docsearch:version" content="current"><meta data-rh="true" name="docsearch:docusaurus_tag" content="docs-default-current"><meta data-rh="true" property="og:title" content="DNS | Rancher"><meta data-rh="true" name="description" content="The commands/steps listed on this page can be used to check name resolution issues in your cluster."><meta data-rh="true" property="og:description" content="The commands/steps listed on this page can be used to check name resolution issues in your cluster."><link data-rh="true" rel="icon" href="/img/favicon.png"><link data-rh="true" rel="canonical" href="https://ranchermanager.docs.rancher.com/troubleshooting/other-troubleshooting-tips/dns"><link data-rh="true" rel="alternate" href="https://ranchermanager.docs.rancher.com/troubleshooting/other-troubleshooting-tips/dns" hreflang="en"><link data-rh="true" rel="alternate" href="https://ranchermanager.docs.rancher.com/zh/troubleshooting/other-troubleshooting-tips/dns" hreflang="zh"><link data-rh="true" rel="alternate" href="https://ranchermanager.docs.rancher.com/troubleshooting/other-troubleshooting-tips/dns" hreflang="x-default"><link data-rh="true" rel="preconnect" href="https://30NEY6C9UY-dsn.algolia.net" crossorigin="anonymous"><link rel="preconnect" href="https://www.googletagmanager.com">
<script>window.dataLayer=window.dataLayer||[]</script>
<script>!function(e,t,a,n,g){e[n]=e[n]||[],e[n].push({"gtm.start":(new Date).getTime(),event:"gtm.js"});var m=t.getElementsByTagName(a)[0],r=t.createElement(a);r.async=!0,r.src="https://www.googletagmanager.com/gtm.js?id=GTM-57KS2MW",m.parentNode.insertBefore(r,m)}(window,document,"script","dataLayer")</script>
<link rel="search" type="application/opensearchdescription+xml" title="Rancher" href="/opensearch.xml">
<script src="https://cdn.cookielaw.org/scripttemplates/otSDKStub.js" charset="UTF-8" data-domain-script="0f98beb0-fc4c-417d-a42e-564e2cae42d2" async></script>
<script src="/scripts/optanonwrapper.js" async></script><link rel="stylesheet" href="/assets/css/styles.efd70281.css">
<link rel="preload" href="/assets/js/runtime~main.5e8050ed.js" as="script">
<link rel="preload" href="/assets/js/main.7c8ccb50.js" as="script">
</head>
<body class="navigation-with-keyboard">
<noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-57KS2MW" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>
<script>!function(){function t(t){document.documentElement.setAttribute("data-theme",t)}var e=function(){var t=null;try{t=localStorage.getItem("theme")}catch(t){}return t}();t(null!==e?e:"light")}()</script><div id="__docusaurus">
<div role="region" aria-label="Skip to main content"><a class="skipToContent_fXgn" href="#docusaurus_skipToContent_fallback">Skip to main content</a></div><nav aria-label="Main" class="navbar navbar--fixed-top"><div class="navbar__inner"><div class="navbar__items"><button aria-label="Toggle navigation bar" aria-expanded="false" class="navbar__toggle clean-btn" type="button"><svg width="30" height="30" viewBox="0 0 30 30" aria-hidden="true"><path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path></svg></button><a class="navbar__brand" href="/"><div class="navbar__logo"><img src="/img/rancher-logo-horiz-color.svg" alt="logo" class="themedImage_ToTc themedImage--light_HNdA"><img src="/img/rancher-logo-horiz-color.svg" alt="logo" class="themedImage_ToTc themedImage--dark_i4oU"></div><b class="navbar__title text--truncate"></b></a><div class="navbar__item dropdown dropdown--hoverable"><a aria-current="page" class="navbar__link active" aria-haspopup="true" aria-expanded="false" role="button" href="/">Latest</a><ul class="dropdown__menu"><li><a aria-current="page" class="dropdown__link dropdown__link--active" href="/troubleshooting/other-troubleshooting-tips/dns">Latest</a></li><li><a class="dropdown__link" href="/v2.7/troubleshooting/other-troubleshooting-tips/dns">v2.7</a></li><li><a class="dropdown__link" href="/v2.6/troubleshooting/other-troubleshooting-tips/dns">v2.6</a></li><li><a class="dropdown__link" href="/v2.5/troubleshooting/other-troubleshooting-tips/dns">v2.5</a></li><li><a class="dropdown__link" href="/v2.0-v2.4/troubleshooting/other-troubleshooting-tips/dns">v2.0-v2.4</a></li><li><a class="dropdown__link" href="/versions">All versions</a></li></ul></div></div><div class="navbar__items navbar__items--right"><div class="navbar__item dropdown dropdown--hoverable dropdown--right"><a href="#" aria-haspopup="true" aria-expanded="false" role="button" class="navbar__link"><svg viewBox="0 0 24 24" width="20" height="20" aria-hidden="true" class="iconLanguage_nlXk"><path fill="currentColor" d="M12.87 15.07l-2.54-2.51.03-.03c1.74-1.94 2.98-4.17 3.71-6.53H17V4h-7V2H8v2H1v1.99h11.17C11.5 7.92 10.44 9.75 9 11.35 8.07 10.32 7.3 9.19 6.69 8h-2c.73 1.63 1.73 3.17 2.98 4.56l-5.09 5.02L4 19l5-5 3.11 3.11.76-2.04zM18.5 10h-2L12 22h2l1.12-3h4.75L21 22h2l-4.5-12zm-2.62 7l1.62-4.33L19.12 17h-3.24z"></path></svg>English</a><ul class="dropdown__menu"><li><a href="/troubleshooting/other-troubleshooting-tips/dns" target="_self" rel="noopener noreferrer" class="dropdown__link dropdown__link--active" lang="en">English</a></li><li><a href="/zh/troubleshooting/other-troubleshooting-tips/dns" target="_self" rel="noopener noreferrer" class="dropdown__link" lang="zh">简体中文</a></li></ul></div><a href="https://github.com/rancher/rancher-docs" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link navbar__github">GitHub<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a><a href="https://www.rancher.com" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link">Rancher Home<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a><div class="searchBox_ZlJk"><button type="button" class="DocSearch DocSearch-Button" aria-label="Search"><span class="DocSearch-Button-Container"><svg width="20" height="20" class="DocSearch-Search-Icon" viewBox="0 0 20 20"><path d="M14.386 14.386l4.0877 4.0877-4.0877-4.0877c-2.9418 2.9419-7.7115 2.9419-10.6533 0-2.9419-2.9418-2.9419-7.7115 0-10.6533 2.9418-2.9419 7.7115-2.9419 10.6533 0 2.9419 2.9418 2.9419 7.7115 0 10.6533z" stroke="currentColor" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg><span class="DocSearch-Button-Placeholder">Search</span></span><span class="DocSearch-Button-Keys"></span></button></div></div></div><div role="presentation" class="navbar-sidebar__backdrop"></div></nav><div id="docusaurus_skipToContent_fallback" class="main-wrapper mainWrapper_z2l0 docsWrapper_BCFX"><button aria-label="Scroll back to top" class="clean-btn theme-back-to-top-button backToTopButton_sjWU" type="button"></button><div class="docPage__5DB"><aside class="theme-doc-sidebar-container docSidebarContainer_b6E3"><div class="sidebarViewport_Xe31"><div class="sidebar_njMd"><nav aria-label="Docs sidebar" class="menu thin-scrollbar menu_SIkG"><ul class="theme-doc-sidebar-menu menu__list"><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-1 menu__list-item"><a class="menu__link" href="/">What is Rancher?</a></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/getting-started/overview">Getting Started</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/pages-for-subheaders/new-user-guides">How-to Guides</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/pages-for-subheaders/best-practices">Reference Guides</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/pages-for-subheaders/cloud-marketplace">Integrations in Rancher</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/faq/general-faq">FAQ</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret menu__link--active" aria-expanded="true" href="/troubleshooting/general-troubleshooting">Troubleshooting</a></div><ul style="display:block;overflow:visible;height:auto" class="menu__list"><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/troubleshooting/general-troubleshooting">General Troubleshooting</a></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-2 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist" aria-expanded="false" tabindex="0" href="/pages-for-subheaders/kubernetes-components">Kubernetes Components</a><button aria-label="Toggle the collapsible sidebar category &#x27;Kubernetes Components&#x27;" type="button" class="clean-btn menu__caret"></button></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-2 menu__list-item"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret menu__link--active" aria-expanded="true" tabindex="0" href="/troubleshooting/other-troubleshooting-tips/kubernetes-resources">Other Troubleshooting Tips</a></div><ul style="display:block;overflow:visible;height:auto" class="menu__list"><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="/troubleshooting/other-troubleshooting-tips/kubernetes-resources">Kubernetes Resources</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="/troubleshooting/other-troubleshooting-tips/networking">Networking</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link menu__link--active" aria-current="page" tabindex="0" href="/troubleshooting/other-troubleshooting-tips/dns">DNS</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="/troubleshooting/other-troubleshooting-tips/rancher-ha">Rancher HA</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="/troubleshooting/other-troubleshooting-tips/registered-clusters">Registered Clusters</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="/troubleshooting/other-troubleshooting-tips/logging">Logging</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="/troubleshooting/other-troubleshooting-tips/user-id-tracking-in-audit-logs">User ID Tracking in Audit Logs</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="/troubleshooting/other-troubleshooting-tips/expired-webhook-certificate-rotation">Rotation of Expired Webhook Certificates</a></li></ul></li></ul></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-1 menu__list-item"><a class="menu__link" href="/contribute-to-rancher">Contributing to Rancher</a></li></ul></nav></div></div></aside><main class="docMainContainer_gTbr"><div class="container padding-top--md padding-bottom--lg"><div class="row"><div class="col docItemCol_VOVn"><div class="docItemContainer_Djhp"><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" aria-label="Breadcrumbs"><ul class="breadcrumbs" itemscope="" itemtype="https://schema.org/BreadcrumbList"><li class="breadcrumbs__item"><a aria-label="Home page" class="breadcrumbs__link" href="/"><svg viewBox="0 0 24 24" class="breadcrumbHomeIcon_YNFT"><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill="currentColor"></path></svg></a></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">Troubleshooting</span><meta itemprop="position" content="1"></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">Other Troubleshooting Tips</span><meta itemprop="position" content="2"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">DNS</span><meta itemprop="position" content="3"></li></ul></nav><span class="theme-doc-version-badge badge badge--secondary">Version: Latest</span><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><header><h1>DNS</h1></header><p>The commands/steps listed on this page can be used to check name resolution issues in your cluster.</p><p>Make sure you configured the correct kubeconfig (for example, <code>export KUBECONFIG=$PWD/kube_config_cluster.yml</code> for Rancher HA) or are using the embedded kubectl via the UI.</p><p>Before running the DNS checks, check the <a href="/reference-guides/cluster-configuration/rancher-server-configuration/rke1-cluster-configuration#default-dns-provider">default DNS provider</a> for your cluster and make sure that <a href="/troubleshooting/other-troubleshooting-tips/networking#check-if-overlay-network-is-functioning-correctly">the overlay network is functioning correctly</a> as this can also be the reason why DNS resolution (partly) fails.</p><h3 class="anchor anchorWithStickyNavbar_LWe7" id="check-if-dns-pods-are-running">Check if DNS pods are running<a href="#check-if-dns-pods-are-running" class="hash-link" aria-label="Direct link to Check if DNS pods are running" title="Direct link to Check if DNS pods are running">​</a></h3><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl -n kube-system get pods -l k8s-app=kube-dns</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Example output when using CoreDNS:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">NAME READY STATUS RESTARTS AGE</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">coredns-799dffd9c4-6jhlz 1/1 Running 0 76m</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Example output when using kube-dns:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">NAME READY STATUS RESTARTS AGE</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">kube-dns-5fd74c7488-h6f7n 3/3 Running 0 4m13s</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h3 class="anchor anchorWithStickyNavbar_LWe7" id="check-if-the-dns-service-is-present-with-the-correct-cluster-ip">Check if the DNS service is present with the correct cluster-ip<a href="#check-if-the-dns-service-is-present-with-the-correct-cluster-ip" class="hash-link" aria-label="Direct link to Check if the DNS service is present with the correct cluster-ip" title="Direct link to Check if the DNS service is present with the correct cluster-ip">​</a></h3><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl -n kube-system get svc -l k8s-app=kube-dns</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">service/kube-dns ClusterIP 10.43.0.10 &lt;none&gt; 53/UDP,53/TCP 4m13s</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h3 class="anchor anchorWithStickyNavbar_LWe7" id="check-if-domain-names-are-resolving">Check if domain names are resolving<a href="#check-if-domain-names-are-resolving" class="hash-link" aria-label="Direct link to Check if domain names are resolving" title="Direct link to Check if domain names are resolving">​</a></h3><p>Check if internal cluster names are resolving (in this example, <code>kubernetes.default</code>), the IP shown after <code>Server:</code> should be the same as the <code>CLUSTER-IP</code> from the <code>kube-dns</code> service.</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl run -it --rm --restart=Never busybox --image=busybox:1.28 -- nslookup kubernetes.default</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Example output:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">Server: 10.43.0.10</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">Address 1: 10.43.0.10 kube-dns.kube-system.svc.cluster.local</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">Name: kubernetes.default</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">Address 1: 10.43.0.1 kubernetes.default.svc.cluster.local</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">pod &quot;busybox&quot; deleted</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Check if external names are resolving (in this example, <code>www.google.com</code>)</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl run -it --rm --restart=Never busybox --image=busybox:1.28 -- nslookup www.google.com</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Example output:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">Server: 10.43.0.10</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">Address 1: 10.43.0.10 kube-dns.kube-system.svc.cluster.local</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">Name: www.google.com</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">Address 1: 2a00:1450:4009:80b::2004 lhr35s04-in-x04.1e100.net</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">Address 2: 216.58.211.100 ams15s32-in-f4.1e100.net</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">pod &quot;busybox&quot; deleted</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>If you want to check resolving of domain names on all of the hosts, execute the following steps:</p><ol><li><p>Save the following file as <code>ds-dnstest.yml</code></p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">apiVersion: apps/v1</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">kind: DaemonSet</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">metadata:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> name: dnstest</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">spec:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> selector:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> matchLabels:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> name: dnstest</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> template:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> metadata:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> labels:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> name: dnstest</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> spec:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> tolerations:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> - operator: Exists</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> containers:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> - image: busybox:1.28</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> imagePullPolicy: Always</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> name: alpine</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> command: [&quot;sh&quot;, &quot;-c&quot;, &quot;tail -f /dev/null&quot;]</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> terminationMessagePath: /dev/termination-log</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></li><li><p>Launch it using <code>kubectl create -f ds-dnstest.yml</code></p></li><li><p>Wait until <code>kubectl rollout status ds/dnstest -w</code> returns: <code>daemon set &quot;dnstest&quot; successfully rolled out</code>.</p></li><li><p>Configure the environment variable <code>DOMAIN</code> to a fully qualified domain name (FQDN) that the host should be able to resolve (<code>www.google.com</code> is used as an example) and run the following command to let each container on every host resolve the configured domain name (it&#x27;s a single line command).</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">export DOMAIN=www.google.com; echo &quot;=&gt; Start DNS resolve test&quot;; kubectl get pods -l name=dnstest --no-headers -o custom-columns=NAME:.metadata.name,HOSTIP:.status.hostIP | while read pod host; do kubectl exec $pod -- /bin/sh -c &quot;nslookup $DOMAIN &gt; /dev/null 2&gt;&amp;1&quot;; RC=$?; if [ $RC -ne 0 ]; then echo $host cannot resolve $DOMAIN; fi; done; echo &quot;=&gt; End DNS resolve test&quot;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></li><li><p>When this command has finished running, the output indicating everything is correct is:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">=&gt; Start DNS resolve test</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">=&gt; End DNS resolve test</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></li></ol><p>If you see error in the output, that means that the mentioned host(s) is/are not able to resolve the given FQDN.</p><p>Example error output of a situation where host with IP 209.97.182.150 had the UDP ports blocked.</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">=&gt; Start DNS resolve test</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">command terminated with exit code 1</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">209.97.182.150 cannot resolve www.google.com</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">=&gt; End DNS resolve test</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Cleanup the alpine DaemonSet by running <code>kubectl delete ds/dnstest</code>.</p><h3 class="anchor anchorWithStickyNavbar_LWe7" id="coredns-specific">CoreDNS specific<a href="#coredns-specific" class="hash-link" aria-label="Direct link to CoreDNS specific" title="Direct link to CoreDNS specific">​</a></h3><h4 class="anchor anchorWithStickyNavbar_LWe7" id="check-coredns-logging">Check CoreDNS logging<a href="#check-coredns-logging" class="hash-link" aria-label="Direct link to Check CoreDNS logging" title="Direct link to Check CoreDNS logging">​</a></h4><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl -n kube-system logs -l k8s-app=kube-dns</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h4 class="anchor anchorWithStickyNavbar_LWe7" id="check-configuration">Check configuration<a href="#check-configuration" class="hash-link" aria-label="Direct link to Check configuration" title="Direct link to Check configuration">​</a></h4><p>CoreDNS configuration is stored in the configmap <code>coredns</code> in the <code>kube-system</code> namespace.</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl -n kube-system get configmap coredns -o go-template={{.data.Corefile}}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h4 class="anchor anchorWithStickyNavbar_LWe7" id="check-upstream-nameservers-in-resolvconf">Check upstream nameservers in resolv.conf<a href="#check-upstream-nameservers-in-resolvconf" class="hash-link" aria-label="Direct link to Check upstream nameservers in resolv.conf" title="Direct link to Check upstream nameservers in resolv.conf">​</a></h4><p>By default, the configured nameservers on the host (in <code>/etc/resolv.conf</code>) will be used as upstream nameservers for CoreDNS. You can check this file on the host or run the following Pod with <code>dnsPolicy</code> set to <code>Default</code>, which will inherit the <code>/etc/resolv.conf</code> from the host it is running on.</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl run -i --restart=Never --rm test-${RANDOM} --image=ubuntu --overrides=&#x27;{&quot;kind&quot;:&quot;Pod&quot;, &quot;apiVersion&quot;:&quot;v1&quot;, &quot;spec&quot;: {&quot;dnsPolicy&quot;:&quot;Default&quot;}}&#x27; -- sh -c &#x27;cat /etc/resolv.conf&#x27;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h4 class="anchor anchorWithStickyNavbar_LWe7" id="enable-query-logging">Enable query logging<a href="#enable-query-logging" class="hash-link" aria-label="Direct link to Enable query logging" title="Direct link to Enable query logging">​</a></h4><p>Enabling query logging can be done by enabling the <a href="https://coredns.io/plugins/log/" target="_blank" rel="noopener noreferrer">log plugin</a> in the Corefile configuration in the configmap <code>coredns</code>. You can do so by using <code>kubectl -n kube-system edit configmap coredns</code> or use the command below to replace the configuration in place:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl get configmap -n kube-system coredns -o json | sed -e &#x27;s_loadbalance_log\\n loadbalance_g&#x27; | kubectl apply -f -</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>All queries will now be logged and can be checked using the command in <a href="#check-coredns-logging">Check CoreDNS logging</a>.</p><h3 class="anchor anchorWithStickyNavbar_LWe7" id="kube-dns-specific">kube-dns specific<a href="#kube-dns-specific" class="hash-link" aria-label="Direct link to kube-dns specific" title="Direct link to kube-dns specific">​</a></h3><h4 class="anchor anchorWithStickyNavbar_LWe7" id="check-upstream-nameservers-in-kubedns-container">Check upstream nameservers in kubedns container<a href="#check-upstream-nameservers-in-kubedns-container" class="hash-link" aria-label="Direct link to Check upstream nameservers in kubedns container" title="Direct link to Check upstream nameservers in kubedns container">​</a></h4><p>By default, the configured nameservers on the host (in <code>/etc/resolv.conf</code>) will be used as upstream nameservers for kube-dns. Sometimes the host will run a local caching DNS nameserver, which means the address in <code>/etc/resolv.conf</code> will point to an address in the loopback range (<code>127.0.0.0/8</code>) which will be unreachable by the container. In case of Ubuntu 18.04, this is done by <code>systemd-resolved</code>. We detect if <code>systemd-resolved</code> is running, and will automatically use the <code>/etc/resolv.conf</code> file with the correct upstream nameservers (which is located at <code>/run/systemd/resolve/resolv.conf</code>).</p><p>Use the following command to check the upstream nameservers used by the kubedns container:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl -n kube-system get pods -l k8s-app=kube-dns --no-headers -o custom-columns=NAME:.metadata.name,HOSTIP:.status.hostIP | while read pod host; do echo &quot;Pod ${pod} on host ${host}&quot;; kubectl -n kube-system exec $pod -c kubedns cat /etc/resolv.conf; done</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Example output:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">Pod kube-dns-667c7cb9dd-z4dsf on host x.x.x.x</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">nameserver 1.1.1.1</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">nameserver 8.8.4.4</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>If the output shows an address in the loopback range (<code>127.0.0.0/8</code>), you can correct this in two ways:</p><ul><li>Make sure the correct nameservers are listed in <code>/etc/resolv.conf</code> on your nodes in the cluster, please consult your operating system documentation on how to do this. Make sure you execute this before provisioning a cluster, or reboot the nodes after making the modification.</li><li>Configure the <code>kubelet</code> to use a different file for resolving names, by using <code>extra_args</code> as shown below (where <code>/run/resolvconf/resolv.conf</code> is the file with the correct nameservers):</li></ul><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">services:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> kubelet:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> extra_args:</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> resolv-conf: &quot;/run/resolvconf/resolv.conf&quot;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><div class="theme-admonition theme-admonition-note alert alert--secondary admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 14 16"><path fill-rule="evenodd" d="M6.3 5.69a.942.942 0 0 1-.28-.7c0-.28.09-.52.28-.7.19-.18.42-.28.7-.28.28 0 .52.09.7.28.18.19.28.42.28.7 0 .28-.09.52-.28.7a1 1 0 0 1-.7.3c-.28 0-.52-.11-.7-.3zM8 7.99c-.02-.25-.11-.48-.31-.69-.2-.19-.42-.3-.69-.31H6c-.27.02-.48.13-.69.31-.2.2-.3.44-.31.69h1v3c.02.27.11.5.31.69.2.2.42.31.69.31h1c.27 0 .48-.11.69-.31.2-.19.3-.42.31-.69H8V7.98v.01zM7 2.3c-3.14 0-5.7 2.54-5.7 5.68 0 3.14 2.56 5.7 5.7 5.7s5.7-2.55 5.7-5.7c0-3.15-2.56-5.69-5.7-5.69v.01zM7 .98c3.86 0 7 3.14 7 7s-3.14 7-7 7-7-3.12-7-7 3.14-7 7-7z"></path></svg></span>note</div><div class="admonitionContent_S0QG"><p>As the <code>kubelet</code> is running inside a container, the path for files located in <code>/etc</code> and <code>/usr</code> are in <code>/host/etc</code> and <code>/host/usr</code> inside the <code>kubelet</code> container.</p></div></div><p>See <a href="/reference-guides/cluster-configuration/rancher-server-configuration/rke1-cluster-configuration#editing-clusters-with-yaml">Editing Cluster as YAML</a> how to apply this change. When the provisioning of the cluster has finished, you have to remove the kube-dns pod to activate the new setting in the pod:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl delete pods -n kube-system -l k8s-app=kube-dns</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">pod &quot;kube-dns-5fd74c7488-6pwsf&quot; deleted</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Try to resolve name again using <a href="#check-if-domain-names-are-resolving">Check if domain names are resolving</a>.</p><p>If you want to check the kube-dns configuration in your cluster (for example, to check if there are different upstream nameservers configured), you can run the following command to list the kube-dns configuration:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">kubectl -n kube-system get configmap kube-dns -o go-template=&#x27;{{range $key, $value := .data}}{{ $key }}{{&quot;:&quot;}}{{ $value }}{{&quot;\n&quot;}}{{end}}&#x27;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Example output:</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">upstreamNameservers:[&quot;1.1.1.1&quot;]</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="theme-doc-footer-edit-meta-row row"><div class="col"><a href="https://github.com/rancher/rancher-docs/edit/main/docs/troubleshooting/other-troubleshooting-tips/dns.md" target="_blank" rel="noreferrer noopener" class="theme-edit-this-page"><svg fill="currentColor" height="20" width="20" viewBox="0 0 40 40" class="iconEdit_Z9Sw" aria-hidden="true"><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"></path></g></svg>Edit this page</a></div><div class="col lastUpdated_vwxv"><span class="theme-last-updated">Last updated<!-- --> on <b><time datetime="2023-06-01T21:19:12.000Z">Jun 1, 2023</time></b></span></div></div></footer></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages navigation"><a class="pagination-nav__link pagination-nav__link--prev" href="/troubleshooting/other-troubleshooting-tips/networking"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">Networking</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/troubleshooting/other-troubleshooting-tips/rancher-ha"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">Rancher HA</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#check-if-dns-pods-are-running" class="table-of-contents__link toc-highlight">Check if DNS pods are running</a></li><li><a href="#check-if-the-dns-service-is-present-with-the-correct-cluster-ip" class="table-of-contents__link toc-highlight">Check if the DNS service is present with the correct cluster-ip</a></li><li><a href="#check-if-domain-names-are-resolving" class="table-of-contents__link toc-highlight">Check if domain names are resolving</a></li><li><a href="#coredns-specific" class="table-of-contents__link toc-highlight">CoreDNS specific</a></li><li><a href="#kube-dns-specific" class="table-of-contents__link toc-highlight">kube-dns specific</a></li></ul></div></div></div></div></main></div></div><footer class="footer footer--dark"><div class="container container-fluid"><div class="footer__bottom text--center"><div class="footer__copyright">Copyright © 2023 SUSE Rancher. All Rights Reserved.</div></div></div></footer></div>
<script src="/assets/js/runtime~main.5e8050ed.js"></script>
<script src="/assets/js/main.7c8ccb50.js"></script>
</body>
</html>