{"id":6288,"date":"2019-07-26T18:43:59","date_gmt":"2019-07-26T18:43:59","guid":{"rendered":"https:\/\/www.devopsschool.com\/blog\/?p=6288"},"modified":"2021-11-16T11:12:11","modified_gmt":"2021-11-16T11:12:11","slug":"working-with-kubernetes-cluster-using-kubectl-part-7-labels","status":"publish","type":"post","link":"https:\/\/www.devopsschool.com\/blog\/working-with-kubernetes-cluster-using-kubectl-part-7-labels\/","title":{"rendered":"Working with Kubernetes Cluster using Kubectl Part &#8211; 7 &#8211; Labels"},"content":{"rendered":"\n<p><strong>PodsToNodes.yaml<\/strong><\/p>\n\n\n<pre class=\"wp-block-code\"><span><code class=\"hljs\">apiVersion: v1\nkind: Pod\nmetadata:\n  name: nginx-pod-ssd\nspec:\n  containers:\n  - name: nginx\n    image: nginx\n    ports:\n    - containerPort: 80\n  nodeSelector:\n    disk: local_ssd\n---\napiVersion: v1\nkind: Pod\nmetadata:\n  name: nginx-pod-gpu\nspec:\n  containers:\n  - name: nginx\n    image: nginx\n    ports:\n    - containerPort: 80\n  nodeSelector:\n    hardware: local_gpu\n---\napiVersion: v1\nkind: Pod\nmetadata:\n  name: nginx-pod\nspec:\n  containers:\n  - name: nginx\n    image: nginx\n    ports:\n    - containerPort: 80\n\n<\/code><\/span><\/pre>\n\n\n<p><strong>CreatePodsWithLabels.yaml<\/strong><\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-1\" data-shcb-language-name=\"CSS\" data-shcb-language-slug=\"css\"><span><code class=\"hljs language-css\"><span class=\"hljs-selector-tag\">apiVersion<\/span>: <span class=\"hljs-selector-tag\">v1<\/span>\n<span class=\"hljs-selector-tag\">kind<\/span>: <span class=\"hljs-selector-tag\">Pod<\/span>\n<span class=\"hljs-selector-tag\">metadata<\/span>:\n  <span class=\"hljs-selector-tag\">name<\/span>: <span class=\"hljs-selector-tag\">nginx-pod-1<\/span>\n  <span class=\"hljs-selector-tag\">labels<\/span>: \n    <span class=\"hljs-selector-tag\">app<\/span>: <span class=\"hljs-selector-tag\">MyWebApp<\/span>\n    <span class=\"hljs-selector-tag\">deployment<\/span>: <span class=\"hljs-selector-tag\">v1<\/span>\n    <span class=\"hljs-selector-tag\">tier<\/span>: <span class=\"hljs-selector-tag\">prod<\/span>\n<span class=\"hljs-selector-tag\">spec<\/span>:\n  <span class=\"hljs-selector-tag\">containers<\/span>:\n  <span class=\"hljs-selector-tag\">-<\/span> <span class=\"hljs-selector-tag\">name<\/span>: <span class=\"hljs-selector-tag\">nginx<\/span>\n    <span class=\"hljs-selector-tag\">image<\/span>: <span class=\"hljs-selector-tag\">nginx<\/span>\n    <span class=\"hljs-selector-tag\">ports<\/span>:\n    <span class=\"hljs-selector-tag\">-<\/span> <span class=\"hljs-selector-tag\">containerPort<\/span>: 80\n<span class=\"hljs-selector-tag\">---<\/span>\n<span class=\"hljs-selector-tag\">apiVersion<\/span>: <span class=\"hljs-selector-tag\">v1<\/span>\n<span class=\"hljs-selector-tag\">kind<\/span>: <span class=\"hljs-selector-tag\">Pod<\/span>\n<span class=\"hljs-selector-tag\">metadata<\/span>:\n  <span class=\"hljs-selector-tag\">name<\/span>: <span class=\"hljs-selector-tag\">nginx-pod-2<\/span>\n  <span class=\"hljs-selector-tag\">labels<\/span>: \n    <span class=\"hljs-selector-tag\">app<\/span>: <span class=\"hljs-selector-tag\">MyWebApp<\/span>\n    <span class=\"hljs-selector-tag\">deployment<\/span>: <span class=\"hljs-selector-tag\">v1<\/span><span class=\"hljs-selector-class\">.1<\/span>\n    <span class=\"hljs-selector-tag\">tier<\/span>: <span class=\"hljs-selector-tag\">prod<\/span>\n<span class=\"hljs-selector-tag\">spec<\/span>:\n  <span class=\"hljs-selector-tag\">containers<\/span>:\n  <span class=\"hljs-selector-tag\">-<\/span> <span class=\"hljs-selector-tag\">name<\/span>: <span class=\"hljs-selector-tag\">nginx<\/span>\n    <span class=\"hljs-selector-tag\">image<\/span>: <span class=\"hljs-selector-tag\">nginx<\/span>\n    <span class=\"hljs-selector-tag\">ports<\/span>:\n    <span class=\"hljs-selector-tag\">-<\/span> <span class=\"hljs-selector-tag\">containerPort<\/span>: 80\n<span class=\"hljs-selector-tag\">---<\/span>\n<span class=\"hljs-selector-tag\">apiVersion<\/span>: <span class=\"hljs-selector-tag\">v1<\/span>\n<span class=\"hljs-selector-tag\">kind<\/span>: <span class=\"hljs-selector-tag\">Pod<\/span>\n<span class=\"hljs-selector-tag\">metadata<\/span>:\n  <span class=\"hljs-selector-tag\">name<\/span>: <span class=\"hljs-selector-tag\">nginx-pod-3<\/span>\n  <span class=\"hljs-selector-tag\">labels<\/span>: \n    <span class=\"hljs-selector-tag\">app<\/span>: <span class=\"hljs-selector-tag\">MyWebApp<\/span>\n    <span class=\"hljs-selector-tag\">deployment<\/span>: <span class=\"hljs-selector-tag\">v1<\/span><span class=\"hljs-selector-class\">.1<\/span>\n    <span class=\"hljs-selector-tag\">tier<\/span>: <span class=\"hljs-selector-tag\">qa<\/span>\n<span class=\"hljs-selector-tag\">spec<\/span>:\n  <span class=\"hljs-selector-tag\">containers<\/span>:\n  <span class=\"hljs-selector-tag\">-<\/span> <span class=\"hljs-selector-tag\">name<\/span>: <span class=\"hljs-selector-tag\">nginx<\/span>\n    <span class=\"hljs-selector-tag\">image<\/span>: <span class=\"hljs-selector-tag\">nginx<\/span>\n    <span class=\"hljs-selector-tag\">ports<\/span>:\n    <span class=\"hljs-selector-tag\">-<\/span> <span class=\"hljs-selector-tag\">containerPort<\/span>: 80\n<span class=\"hljs-selector-tag\">---<\/span>\n<span class=\"hljs-selector-tag\">apiVersion<\/span>: <span class=\"hljs-selector-tag\">v1<\/span>\n<span class=\"hljs-selector-tag\">kind<\/span>: <span class=\"hljs-selector-tag\">Pod<\/span>\n<span class=\"hljs-selector-tag\">metadata<\/span>:\n  <span class=\"hljs-selector-tag\">name<\/span>: <span class=\"hljs-selector-tag\">nginx-pod-4<\/span>\n  <span class=\"hljs-selector-tag\">labels<\/span>: \n    <span class=\"hljs-selector-tag\">app<\/span>: <span class=\"hljs-selector-tag\">MyAdminApp<\/span>\n    <span class=\"hljs-selector-tag\">deployment<\/span>: <span class=\"hljs-selector-tag\">v1<\/span>\n    <span class=\"hljs-selector-tag\">tier<\/span>: <span class=\"hljs-selector-tag\">prod<\/span>\n<span class=\"hljs-selector-tag\">spec<\/span>:\n  <span class=\"hljs-selector-tag\">containers<\/span>:\n  <span class=\"hljs-selector-tag\">-<\/span> <span class=\"hljs-selector-tag\">name<\/span>: <span class=\"hljs-selector-tag\">nginx<\/span>\n    <span class=\"hljs-selector-tag\">image<\/span>: <span class=\"hljs-selector-tag\">nginx<\/span>\n    <span class=\"hljs-selector-tag\">ports<\/span>:\n    <span class=\"hljs-selector-tag\">-<\/span> <span class=\"hljs-selector-tag\">containerPort<\/span>: 80\n<span class=\"hljs-selector-tag\">---<\/span>\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-1\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">CSS<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">css<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p><strong>deployment-label.yaml<\/strong><\/p>\n\n\n<pre class=\"wp-block-code\"><span><code class=\"hljs\">apiVersion: apps\/v1\nkind: Deployment\nmetadata:\n  name: hello-world\n  labels:\n    app: hello-world\nspec:\n  replicas: 4\n  selector:\n    matchLabels:\n      app: hello-world\n  template:\n    metadata:\n      labels:\n        app: hello-world\n    spec:\n      containers:\n      - name: hello-world\n        image: gcr.io\/google-samples\/hello-app:1.0\n        ports:\n        - containerPort: 8080\n<\/code><\/span><\/pre>\n\n\n<p><strong>service.yaml<\/strong><\/p>\n\n\n<pre class=\"wp-block-code\"><span><code class=\"hljs\">apiVersion: v1\nkind: Service\nmetadata:\n  name: hello-world\nspec:\n  ports:\n  - port: 80\n    protocol: TCP\n    targetPort: 8080\n  selector:\n    app: hello-world\n<\/code><\/span><\/pre>\n\n\n<p><strong>Commands<\/strong><\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-2\" data-shcb-language-name=\"PHP\" data-shcb-language-slug=\"php\"><span><code class=\"hljs language-php\"><span class=\"hljs-comment\">#Demo requires nodes c1-master1, c1-node1, c1-node2 and c1-node3<\/span>\nssh aen@c1-master1\ncd ~\/content\/course\/m3\/demos\n\n<span class=\"hljs-comment\">#Create a collection of pods with labels assinged to each<\/span>\nmore CreatePodsWithLabels.yaml\nkubectl apply -f CreatePodsWithLabels.yaml\n\n<span class=\"hljs-comment\">#Look at all the Pod labels in our cluster<\/span>\nkubectl get pods --show-labels\n\n<span class=\"hljs-comment\">#Look at one Pod's labels in our cluster<\/span>\nkubectl describe pod nginx-pod<span class=\"hljs-number\">-1<\/span> | head\n\n<span class=\"hljs-comment\">#Query labels and selectors<\/span>\nkubectl get pods --selector tier=prod\nkubectl get pods --selector tier=qa\nkubectl get pods -l tier=prod\nkubectl get pods -l tier=prod --show-labels\n\n<span class=\"hljs-comment\">#Selector for multiple labels and adding on show-labels to see those labels in the output<\/span>\nkubectl get pods -l <span class=\"hljs-string\">'tier=prod,app=MyWebApp'<\/span> --show-labels\nkubectl get pods -l <span class=\"hljs-string\">'tier=prod,app!=MyWebApp'<\/span> --show-labels\nkubectl get pods -l <span class=\"hljs-string\">'tier in (prod,qa)'<\/span>\nkubectl get pods -l <span class=\"hljs-string\">'tier notin (prod,qa)'<\/span>\n\n<span class=\"hljs-comment\">#Output a particluar label in column format<\/span>\nkubectl get pods -L tier\nkubectl get pods -L tier,app\n\n<span class=\"hljs-comment\">#Edit an existing label<\/span>\nkubectl label pod nginx-pod<span class=\"hljs-number\">-1<\/span> tier=non-prod --overwrite\nkubectl get pod nginx-pod<span class=\"hljs-number\">-1<\/span> --show-labels\n\n<span class=\"hljs-comment\">#Adding a new label<\/span>\nkubectl label pod nginx-pod<span class=\"hljs-number\">-1<\/span> another=Label\nkubectl get pod nginx-pod<span class=\"hljs-number\">-1<\/span> --show-labels\n\n<span class=\"hljs-comment\">#Removing an existing label<\/span>\nkubectl label pod nginx-pod<span class=\"hljs-number\">-1<\/span> another-\nkubectl get pod nginx-pod<span class=\"hljs-number\">-1<\/span> --show-labels\n\n<span class=\"hljs-comment\">#Performing an operation on a collection of pods based on a label query<\/span>\nkubectl label pod --all tier=non-prod --overwrite\nkubectl get pod --show-labels\n\n<span class=\"hljs-comment\">#Delete all pods matching our non-prod label<\/span>\nkubectl delete pod -l tier=non-prod\n\n<span class=\"hljs-comment\">#And we're left with nothing.<\/span>\nkubectl get pods --show-labels\n\n<span class=\"hljs-comment\">#Kubernetes Resource Management<\/span>\n<span class=\"hljs-comment\">#Start a Deployment with 3 replicas, open deployment-label.yaml<\/span>\nkubectl apply -f deployment-label.yaml\n\n<span class=\"hljs-comment\">#Expose our Deployment as  Service, open service.yaml<\/span>\nkubectl apply -f service.yaml\n\n<span class=\"hljs-comment\">#Look at the Labels and Selectors on each resource, the Deployment, ReplicaSet and Pod<\/span>\n<span class=\"hljs-comment\">#The deployment has a selector for app=hello-world<\/span>\nkubectl describe deployment hello-world\n\n<span class=\"hljs-comment\">#The ReplicaSet has labels and selectors for app and the current pod-template-hash<\/span>\n<span class=\"hljs-comment\">#Look at the Pod Template and the labels on the Pods created<\/span>\nkubectl describe replicaset hello-world\n\n<span class=\"hljs-comment\">#The Pods have labels for app=hello-world and for the pod-temlpate-hash of the current ReplicaSet<\/span>\nkubectl get pods --show-labels\n\n<span class=\"hljs-comment\">#Edit the label on one of the Pods in the ReplicaSet, change the pod-template-hash<\/span>\nkubectl label pod hello-world<span class=\"hljs-number\">-5646<\/span>fcc96b-kjvnl pod-template-hash=DEBUG --overwrite\n\n<span class=\"hljs-comment\">#The ReplicaSet will deploy a new Pod to satisfy the number of replicas. Our relabeled Pod still exists.<\/span>\nkubectl get pods --show-labels\n\n<span class=\"hljs-comment\">#Let's look at how Services use labels and selectors, check out services.yaml<\/span>\nkubectl get service\n\n<span class=\"hljs-comment\">#The selector for this serivce is app=hello-world, that pod is still being load balanced to!<\/span>\nkubectl describe service hello-world \n\n<span class=\"hljs-comment\">#Get a list of all IPs in the service, there's 5...why?<\/span>\nkubectl describe endpoints hello-world\n\n<span class=\"hljs-comment\">#Get a list of pods and their IPs<\/span>\nkubectl get pod -o wide\n\n<span class=\"hljs-comment\">#To remove a pod from load balancing, change the label used by the service's selector.<\/span>\n<span class=\"hljs-comment\">#The ReplicaSet will respond by placing another pod in the ReplicaSet<\/span>\nkubectl get pods --show-labels\nkubectl label pod hello-world<span class=\"hljs-number\">-5646<\/span>fcc96b-kjvnl app=DEBUG --overwrite\n\n<span class=\"hljs-comment\">#Check out all the labels in our pods<\/span>\nkubectl get pods --show-labels\n\n<span class=\"hljs-comment\">#Look at the registered endpoint addresses. Now there's 4<\/span>\nkubectl describe endpoints hello-world\n\n<span class=\"hljs-comment\">#To clean up, delete the deployment, service and the Pod removed from the replicaset<\/span>\nkubectl delete deployment hello-world\nkubectl delete service hello-world\nkubectl delete pod hello-world<span class=\"hljs-number\">-5646<\/span>fcc96b-kjvnl\n\n<span class=\"hljs-comment\">#Scheduling a pod to a node<\/span>\n<span class=\"hljs-comment\">#Scheduling is a much deeper topic, we're focusing on how labels can be used to influence it here.<\/span>\nkubectl get nodes --show-labels \n\n<span class=\"hljs-comment\">#Label our nodes with something descriptive<\/span>\nkubectl label node c1-node2 disk=local_ssd\nkubectl label node c1-node3 hardware=local_gpu\n\n<span class=\"hljs-comment\">#Query our labels to confirm.<\/span>\nkubectl get node -L disk,hardware\n\n<span class=\"hljs-comment\">#Create three Pods, two using nodeSelector, one without.<\/span>\nmore PodsToNodes.yaml\nkubectl apply -f PodsToNodes.yaml\n\n<span class=\"hljs-comment\">#View the scheduling of the pods in the cluster.<\/span>\nkubectl get node -L disk,hardware\nkubectl get pods -o wide\n\n<span class=\"hljs-comment\">#Clean up when we're finished, delete our labels and Pods<\/span>\nkubectl label node c1-node2 disk-\nkubectl label node c1-node3 hardware-\nkubectl delete pod nginx-pod\nkubectl delete pod nginx-pod-gpu\nkubectl delete pod nginx-pod-ssd\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-2\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PHP<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">php<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n<div class=\"epyt-gallery\" data-currpage=\"1\" id=\"epyt_gallery_12671\"><iframe loading=\"lazy\"  id=\"_ytid_27856\"  width=\"760\" height=\"427\"  data-origwidth=\"760\" data-origheight=\"427\" src=\"https:\/\/www.youtube.com\/embed\/?enablejsapi=1&#038;autoplay=0&#038;cc_load_policy=0&#038;cc_lang_pref=&#038;iv_load_policy=1&#038;loop=0&#038;rel=1&#038;fs=1&#038;playsinline=0&#038;autohide=2&#038;theme=dark&#038;color=red&#038;controls=1&#038;disablekb=0&#038;\" class=\"__youtube_prefs__  no-lazyload\" title=\"YouTube player\"  data-epytgalleryid=\"epyt_gallery_12671\"  allow=\"fullscreen; accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen data-no-lazy=\"1\" data-skipgform_ajax_framebjll=\"\"><\/iframe><div class=\"epyt-gallery-list\"><div>Sorry, there was a YouTube error.<\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p>PodsToNodes.yaml CreatePodsWithLabels.yaml deployment-label.yaml service.yaml Commands<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_joinchat":[],"footnotes":""},"categories":[4859],"tags":[],"class_list":["post-6288","post","type-post","status-publish","format-standard","hentry","category-kubernetes"],"_links":{"self":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts\/6288","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/comments?post=6288"}],"version-history":[{"count":4,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts\/6288\/revisions"}],"predecessor-version":[{"id":25477,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts\/6288\/revisions\/25477"}],"wp:attachment":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/media?parent=6288"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/categories?post=6288"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/tags?post=6288"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}