{"id":327969,"date":"2021-08-20T13:00:41","date_gmt":"2021-08-20T10:00:41","guid":{"rendered":"https:\/\/en.buradabiliyorum.com\/how-to-debug-kubernetes-imagepullbackoff-errors-cloudsavvy-it\/"},"modified":"2021-08-20T13:00:41","modified_gmt":"2021-08-20T10:00:41","slug":"how-to-debug-kubernetes-imagepullbackoff-errors-cloudsavvy-it","status":"publish","type":"post","link":"https:\/\/buradabiliyorum.com\/en\/how-to-debug-kubernetes-imagepullbackoff-errors-cloudsavvy-it\/","title":{"rendered":"#How to Debug Kubernetes \u201cImagePullBackOff\u201d Errors \u2013 CloudSavvy IT"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_85 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-6a34be83e1257\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #dd3333;color:#dd3333\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #dd3333;color:#dd3333\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-6a34be83e1257\" checked aria-label=\"Toggle\" \/><nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/buradabiliyorum.com\/en\/how-to-debug-kubernetes-imagepullbackoff-errors-cloudsavvy-it\/#How_Image_Pulls_Work\" >How Image Pulls Work<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/buradabiliyorum.com\/en\/how-to-debug-kubernetes-imagepullbackoff-errors-cloudsavvy-it\/#Check_The_Basics\" >Check The Basics<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/buradabiliyorum.com\/en\/how-to-debug-kubernetes-imagepullbackoff-errors-cloudsavvy-it\/#Managing_Registry_Logins\" >Managing Registry Logins<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/buradabiliyorum.com\/en\/how-to-debug-kubernetes-imagepullbackoff-errors-cloudsavvy-it\/#Registry_Rate_Limits\" >Registry Rate Limits<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/buradabiliyorum.com\/en\/how-to-debug-kubernetes-imagepullbackoff-errors-cloudsavvy-it\/#Summary\" >Summary<\/a><\/li><\/ul><\/nav><\/div>\n<p><strong>&#8220;#How to Debug Kubernetes \u201cImagePullBackOff\u201d Errors \u2013 CloudSavvy IT&#8221;<\/strong><\/p>\n<div id=\"article-content-area\">\n<img loading=\"lazy\" decoding=\"async\" class=\"type:primaryImage aligncenter size-full wp-image-9632\" srcset=\"https:\/\/www.cloudsavvyit.com\/p\/uploads\/2021\/02\/748108a6.jpg?width=398&amp;trim=1,1&amp;bg-color=000&amp;pad=1,1 400w, https:\/\/www.cloudsavvyit.com\/p\/uploads\/2021\/02\/748108a6.jpg?width=1198&amp;trim=1,1&amp;bg-color=000&amp;pad=1,1 1200w\" sizes=\"auto, 400w, 1200w\" src=\"https:\/\/www.cloudsavvyit.com\/p\/uploads\/2021\/02\/748108a6.jpg?width=1198&amp;trim=1,1&amp;bg-color=000&amp;pad=1,1\" alt=\"Graphic showing the Kubernetes logo\" width=\"1602\" height=\"902\" onload=\"pagespeed.lazyLoadImages.loadIfVisibleAndMaybeBeacon(this);\" onerror=\"this.onerror=null;pagespeed.lazyLoadImages.loadIfVisibleAndMaybeBeacon(this);\"\/><\/p>\n<p>Kubernetes clusters can encounter several issues while trying to pull your container images. When an error occurs, your Pods will enter an <code>ImagePullBackOff<\/code> state. Here\u2019s how to debug this common but cryptic message so you can get your services online.<\/p>\n<h2 id=\"how-image-pulls-work\"><span class=\"ez-toc-section\" id=\"How_Image_Pulls_Work\"><\/span>How Image Pulls Work<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Kubernetes needs to fetch an image when you create a new deployment or update an existing one with a different tag reference. Responsibility for pulling images lies with the Kubelet process on each worker node. Every image referenced by a Pod\u2019s manifest needs to be accessible to all the nodes in the cluster so that any of them could fulfil a container scheduling request.<\/p>\n<p>The <a href=\"https:\/\/buradabiliyorum.com\/en\/category\/download-scripts-themes-apps\/\" data-internallinksmanager029f6b8e52c=\"9\" title=\"Download Scripts &amp; Themes &amp; Apps\" target=\"_blank\" rel=\"noopener\">download<\/a> could fail if the image path is incorrect, you\u2019re improperly authenticated, or the network goes down. When this happens, Kubernetes \u201cpulls back\u201d and schedules another download attempt. The delay before the next pull increases exponentially each time an attempt fails, <a rel=\"nofollow noopener\" target=\"_blank\" href=\"https:\/\/kubernetes.io\/docs\/concepts\/containers\/images\/#imagepullbackoff\">up to a limit<\/a> of five minutes.<\/p>\n<p>If your Pod shows the <code>ImagePullBackOff<\/code> state, Kubernetes has had multiple successive image pull failures and is now waiting before it retries again. The container won\u2019t be able to start until the image is available.<\/p>\n<p>You can leave the Pod in this state if you know the issue is due to network conditions or another transient error. Kubernetes will eventually complete another retry and successfully acquire the image. If that\u2019s not the case, here\u2019s how to start debugging so you can bring your Pod up.<\/p>\n<h2 id=\"check-the-basics\"><span class=\"ez-toc-section\" id=\"Check_The_Basics\"><\/span>Check The Basics<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>First and foremost, it\u2019s worth checking the very basics. Is your resource manifest referencing a valid image which actually exists? Check the registry path and image tag for simple typos.<\/p>\n<p>You can inspect the internal Kubernetes state with the <code>describe pod<\/code> command in Kubectl. This gives you more information than <code>get pod<\/code> and the Kubernetes dashboard provide.<\/p>\n<pre>kubectl describe pod my-pod --namespace my-namespace<\/pre>\n<p>Changes in the Pod\u2019s lifecycle are displayed under the \u201cEvents\u201d heading. The first event will be <code>Scheduled<\/code>; it should be followed by a <code>Pulling<\/code> event for the first pull attempt. After this, you\u2019ll see a <code>Failed<\/code> or <code>BackOff<\/code> event if the pull couldn\u2019t succeed. These will be repeated later in the list if Kubernetes is still in a back off and retry cycle.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-13882\" src=\"https:\/\/www.cloudsavvyit.com\/p\/uploads\/2021\/08\/561bfd43.png?trim=1,1&amp;bg-color=000&amp;pad=1,1\" alt=\"\" width=\"1582\" height=\"199\" onload=\"pagespeed.lazyLoadImages.loadIfVisibleAndMaybeBeacon(this);\" onerror=\"this.onerror=null;pagespeed.lazyLoadImages.loadIfVisibleAndMaybeBeacon(this);\"\/><\/p>\n<p>Reading the <code>Message<\/code> associated with these events often provides the root cause of the problem. A <code>manifest for image:tag not found<\/code> message means the image is valid but you\u2019ve specified an invalid tag. If you see <code>does not exist or no pull access<\/code>, check the registry and image paths are correct. When you\u2019re sure they\u2019re right, the issue will be related to incorrect authentication.<\/p>\n<h2 id=\"managing-registry-logins\"><span class=\"ez-toc-section\" id=\"Managing_Registry_Logins\"><\/span>Managing Registry Logins<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>You need to be logged in before you pull private images. In Kubernetes, it\u2019s a two-step mechanism: create a secret containing credentials, then reference that secret in your Pod definitions.<\/p>\n<p>The Pod field is called <code>imagePullSecrets<\/code>. It needs to indicate a Kubernetes secret that provides a login token for the registry. This secret should store a Docker-compatible JSON value.<\/p>\n<div class=\"wp-geshi-highlight-wrap5\">\n<div class=\"wp-geshi-highlight-wrap4\">\n<div class=\"wp-geshi-highlight-wrap3\">\n<div class=\"wp-geshi-highlight-wrap2\">\n<div class=\"wp-geshi-highlight-wrap\">\n<div class=\"wp-geshi-highlight\">\n<div class=\"yaml\">\n<pre class=\"de1\"><span class=\"co3\">apiVersion<\/span><span class=\"sy2\">: <\/span>v1<span class=\"co3\">\nkind<\/span><span class=\"sy2\">: <\/span>Secret<span class=\"co3\">\ntype<\/span><span class=\"sy2\">: <\/span>kubernetes.io\/dockerconfigjson<span class=\"co4\">\nmetadata<\/span>:<span class=\"co3\">\n  name<\/span><span class=\"sy2\">: <\/span>image-pull-secret<span class=\"co4\">\ndata<\/span>:<span class=\"co3\">\n  .dockerconfigjson<\/span><span class=\"sy2\">: <\/span><span class=\"br0\">{<\/span><span class=\"br0\">{<\/span> <span class=\"st0\">\"{\"<\/span>auths<span class=\"st0\">\": {\"<\/span>registry.example.com<span class=\"st0\">\": {\"<\/span>username<span class=\"st0\">\": \"<\/span>demo-user<span class=\"st0\">\", \"<\/span>password<span class=\"st0\">\": \"<\/span>my-password<span class=\"st0\">\"}}}\"<\/span> | b64enc <span class=\"br0\">}<\/span><span class=\"br0\">}<\/span>\n<span class=\"co3\">\napiVersion<\/span><span class=\"sy2\">: <\/span>v1<span class=\"co3\">\nkind<\/span><span class=\"sy2\">: <\/span>Pod<span class=\"co4\">\nmetadata<\/span>:<span class=\"co3\">\n  name<\/span><span class=\"sy2\">: <\/span>my-pod<span class=\"co4\">\nspec<\/span>:<span class=\"co4\">\n  containers<\/span>:<span class=\"co3\">\n    - name<\/span><span class=\"sy2\">: <\/span>my-container<span class=\"co3\">\n      image<\/span><span class=\"sy2\">: <\/span>registry.example.com\/my-image:latest<span class=\"co4\">\n  imagePullSecrets<\/span>:<span class=\"co3\">\n    - name<\/span><span class=\"sy2\">: <\/span>image-pull-secret<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<p>This manifest shows how to create a secret that logs you into <code>registry.example.com<\/code> as <code>demo-user<\/code> with the password <code>my-password<\/code>. The Pod references the secret by its name. Kubelet processes on your cluster\u2019s nodes will include the Docker <a rel=\"nofollow noopener\" target=\"_blank\" href=\"https:\/\/docs.docker.com\/config\/daemon\"><code>config.json<\/code><\/a> snippet when they\u2019re pulling images from the registry.<\/p>\n<p>The snippet needs to be Base64-encoded to be a valid Kubernetes secret value. You can use a pre-encoded value or pipe plain text through YAML\u2019s <code>b64enc<\/code>, as shown in the manifest above.<\/p>\n<p>The type of credentials you use will depend on your registry. In many cases, <code>password<\/code> will actually be a personal access token or API key. Docker Hub requires an access token generated in your account settings if you\u2019ve got two-factor authentication enabled on your account.<\/p>\n<h2 id=\"registry-rate-limits\"><span class=\"ez-toc-section\" id=\"Registry_Rate_Limits\"><\/span>Registry Rate Limits<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>If you\u2019ve checked your registry URL, image tag name, and login credentials, you might be seeing <code>ImagePullBackOff<\/code> because of registry rate limits. Docker Hub now restricts you to 100 container pulls every six hours. This increases to 200 pulls per six hours if you supply your login credentials. That cap could be reached quickly in an active cluster with many frequently deployed Pods.<\/p>\n<p>A pull failure due to a rate limit will manifest in the same way as an authentication issue. You\u2019ll need to wait until enough time elapses for the cap to expire. Kubernetes should then successfully pull the image, bringing your Pods up.<\/p>\n<p>For longer-term mitigation, consider running your own in-cluster registry or proxy to cache your images. This can significantly reduce the frequency you hit Docker\u2019s servers, helping you stay within the rate limits.<\/p>\n<h2 id=\"summary\"><span class=\"ez-toc-section\" id=\"Summary\"><\/span>Summary<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Kubernetes Pods enter an <code>ImagePullBackOff<\/code> state when a node fails to pull an image. Kubelet will periodically retry the pull so transient errors don\u2019t require any manual intervention to address.<\/p>\n<p>When you\u2019re sure an <code>ImagePullBackOff<\/code> isn\u2019t just a temporary blip, begin by making sure the Pod\u2019s image path is valid. If that checks out, suspect incorrect login credentials or an exhausted rate limiting allowance. Using <code>kubectl describe<\/code> will expose the sequence of events that led to the failure.<\/p>\n<p>As a final option, you can try pulling the image yourself from another machine to make sure the remote registry server is actually up. If you can pull the image but your cluster can\u2019t, you might have more <a href=\"https:\/\/buradabiliyorum.com\/en\/category\/general\/\" data-internallinksmanager029f6b8e52c=\"3\" title=\"General\" target=\"_blank\" rel=\"noopener\">general<\/a> networking issues preventing your nodes from reaching the registry.\n<\/p><\/div>\n<blockquote><p><strong><span style=\"color: #ff6600;\">If you liked the article, do not forget to share it with your friends. Follow us on\u00a0<span style=\"color: #ff0000;\"><a style=\"color: #ff0000;\" href=\"https:\/\/news.google.com\/publications\/CAAqBwgKMLG0nwswvr63Aw\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">Google News<\/a><\/span>\u00a0too, click on the star and choose us from your favorites.<\/span><\/strong><\/p><\/blockquote>\n<blockquote>\n<p style=\"text-align: center;\">For forums sites go to <span style=\"color: #ff9900;\"><a style=\"color: #ff9900;\" href=\"https:\/\/forum.buradabiliyorum.com\/\" target=\"_blank\" rel=\"noopener\">Forum.BuradaBiliyorum.Com<\/a><\/span><\/strong><\/p>\n<\/blockquote>\n<blockquote>\n<p style=\"text-align: center;\"><strong>If you want to read more like this article, you can visit our <span style=\"color: #ff9900;\"><a style=\"color: #ff9900;\" href=\"https:\/\/en.buradabiliyorum.com\/technology\/\" target=\"_blank\" rel=\"noopener\">Technology category.<\/a><\/span><\/strong><\/p>\n<\/blockquote>\n<p><span style=\"color: black;\"><a style=\"color: #ff9900;\" href=\"https:\/\/www.cloudsavvyit.com\/13880\/how-to-debug-kubernetes-imagepullbackoff-errors\/\" target=\"_blank\" rel=\"noopener\">Source<\/a><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>&#8220;#How to Debug Kubernetes \u201cImagePullBackOff\u201d Errors \u2013 CloudSavvy IT&#8221; Kubernetes clusters can encounter several issues while trying to pull your container images. When an error occurs, your Pods will enter an ImagePullBackOff state. Here\u2019s how to debug this common but cryptic message so you can get your services online. How Image Pulls Work Kubernetes needs&#8230;<\/p>\n","protected":false},"author":1,"featured_media":327970,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"fifu_image_url":"https:\/\/www.cloudsavvyit.com\/p\/uploads\/2021\/02\/748108a6.jpg","fifu_image_alt":"","footnotes":""},"categories":[18],"tags":[],"class_list":["post-327969","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-technology"],"_links":{"self":[{"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/posts\/327969","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/comments?post=327969"}],"version-history":[{"count":0,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/posts\/327969\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/media\/327970"}],"wp:attachment":[{"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/media?parent=327969"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/categories?post=327969"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/tags?post=327969"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}