I have been working on Kubernetes cluster and will soon plan to give a Kubernetes Certified Developer exam. In my quest, I will just record some commands that I found helpful or useful in this blog. It may be multi-part, as I will keep adding on a daily basis the commands that I will be learning.<\/p>\n
Labels<\/h2>\n\n\n
> k get nodes\nNAME STATUS ROLES AGE VERSION\ndocker-desktop Ready,SchedulingDisabled master 105d v1.16.6-beta.0<\/code><\/pre>\n\n\n\n
Adding a label to the node<\/p>\n\n\n\n
> k label node docker-desktop nodeName=docker-node\nnode\/docker-desktop labeled<\/code><\/pre>\n\n\n\n
> k get nodes --show-labels\nNAME STATUS ROLES AGE VERSION LABELS\ndocker-desktop Ready,SchedulingDisabled master 105d v1.16.6-beta.0 beta.kubernetes.io\/arch=amd64,beta.kubernetes.io\/os=linux,kubernetes.io\/arch=amd64,kubernetes.io\/hostname=docker-desktop,kubernetes.io\/os=linux,node-role.kubernetes.io\/master=,nodeName=docker-node<\/code><\/pre>\n\n\n\n
Notice the new label at the end nodeName=docker-node<\/code>. You can also validate the label has been applied by using the selector<\/p>\n\n\n\n
>k get nodes -l nodeName=docker-node\nNAME STATUS ROLES AGE VERSION\ndocker-desktop Ready,SchedulingDisabled master 105d v1.16.6-beta.0<\/code><\/pre>\n\n\n\n
I will create a nginx-pod on my local Docker CE\/Kubernetes <\/code>and validate the Scheduling.<\/p>\n\n\n\n
nodeSelector<\/code> object<\/em><\/td>
NodeSelector is a selector which must be true for the pod to fit on a node. Selector which must match a node’s labels for the pod to be scheduled on that node. More info: https:\/\/kubernetes.io\/docs\/concepts\/configuration\/assign-pod-node\/<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
What I have used is a nodeSelector<\/code> that uses the label define in the section above. As the only node on my local machine is the docker-desktop<\/code> and it has a setting as SchedulingDisabled the container will forever be in the Pending state.<\/p>\n\n\n\n
> k get nodes\nNAME STATUS ROLES AGE VERSION\ndocker-desktop Ready,SchedulingDisabled master 105d v1.16.6-beta.0<\/code><\/pre>\n\n\n\n
> k get all\nNAME READY STATUS RESTARTS AGE\npod\/curl-69c656fd45-zwt8n 1\/1 Running 0 7d\npod\/nginx-node 0\/1 Pending 0 15m<\/code><\/pre>\n\n\n\n
A quick describe on the pod<\/p>\n\n\n\n
> k describe pod\/nginx-node\n\nName: nginx-node\nNamespace: default\nPriority: 0\nNode: <none>\nLabels: app=nginx-on-node\n run=nginx\nAnnotations: kubectl.kubernetes.io\/last-applied-configuration:\n {\"apiVersion\":\"v1\",\"kind\":\"Pod\",\"metadata\":{\"annotations\":{},\"labels\":{\"app\":\"nginx-on-node\",\"run\":\"nginx\"},\"name\":\"nginx-node\",\"namespace...\nStatus: Pending\nIP: \nIPs: <none>\nContainers:\n nginx-container:\n Image: nginx\n Port: <none>\n Host Port: <none>\n Limits:\n cpu: 500m\n memory: 500Mi\n Requests:\n cpu: 500m\n memory: 250Mi\n Environment: <none>\n Mounts:\n \/var\/run\/secrets\/kubernetes.io\/serviceaccount from default-token-ksbmz (ro)\nConditions:\n Type Status\n PodScheduled False \nVolumes:\n default-token-ksbmz:\n Type: Secret (a volume populated by a Secret)\n SecretName: default-token-ksbmz\n Optional: false\nQoS Class: Burstable\nNode-Selectors: nodeName=docker-node\nTolerations: node.kubernetes.io\/not-ready:NoExecute for 300s\n node.kubernetes.io\/unreachable:NoExecute for 300s\nEvents:\n Type Reason Age From Message\n ---- ------ ---- ---- -------\n Warning FailedScheduling <unknown> default-scheduler 0\/1 nodes are available: 1 node(s) were unschedulable.<\/code><\/pre>\n\n\n\n
It validates the un-scedulable<\/code> node. To overcome this handicap, I will use the uncordon<\/code> <\/p>\n\n\n\n
k uncordon -h\nMark node as schedulable.\n\nExamples:\n # Mark node \"foo\" as schedulable.\n $ kubectl uncordon foo\n\nOptions:\n --dry-run=false: If true, only print the object that would be sent, without sending it.\n -l, --selector='': Selector (label query) to filter on\n\nUsage:\n kubectl uncordon NODE [options]<\/code><\/pre>\n\n\n\n
> k uncordon docker-desktop\nnode\/docker-desktop uncordoned<\/code><\/pre>\n\n\n\n
> k get all\nNAME READY STATUS RESTARTS AGE\npod\/curl-69c656fd45-zwt8n 1\/1 Running 0 7d\npod\/nginx-node 0\/1 ContainerCreating 0 7m12s<\/code><\/pre>\n\n\n\n
The moment I mark it as schedulable<\/code> the state changes and I can see the Container creating. A quick describe will show the events<\/p>\n\n\n\n
Type Reason Age From Message\n ---- ------ ---- ---- -------\n Warning FailedScheduling <unknown> default-scheduler 0\/1 nodes are available: 1 node(s) were unschedulable.\n Warning FailedScheduling <unknown> default-scheduler 0\/1 nodes are available: 1 node(s) were unschedulable.\n Warning FailedScheduling <unknown> default-scheduler 0\/1 nodes are available: 1 node(s) had taints that the pod didn't tolerate.\n Normal Scheduled <unknown> default-scheduler Successfully assigned default\/nginx-node to docker-desktop\n Normal Pulling 6m11s kubelet, docker-desktop Pulling image \"nginx\"\n Normal Pulled 6m6s kubelet, docker-desktop Successfully pulled image \"nginx\"\n Normal Created 6m6s kubelet, docker-desktop Created container nginx-container\n Normal Started 6m6s kubelet, docker-desktop Started container nginx-container<\/code><\/pre>\n\n\n\n
Annotations<\/h2>\n\n\n\n
> k annotate pods nginx-node description='My nginx-node on a specific node'\npod\/nginx-node annotated<\/code><\/pre>\n\n\n\n
A describe call for the pod nginx-node<\/code> can reveal the annotation.<\/p>\n\n\n\n
Annotations: description: My nginx-node on a specific node<\/code><\/pre>\n\n\n\n
Create<\/h2>\n\n\n\n
k create -h<\/code><\/p>\n\n\n\n
Available Commands:\n clusterrole Create a ClusterRole.\n clusterrolebinding Create a ClusterRoleBinding for a particular ClusterRole\n configmap Create a configmap from a local file, directory or literal value\n cronjob Create a cronjob with the specified name.\n deployment Create a deployment with the specified name.\n job Create a job with the specified name.\n namespace Create a namespace with the specified name\n poddisruptionbudget Create a pod disruption budget with the specified name.\n priorityclass Create a priorityclass with the specified name.\n quota Create a quota with the specified name.\n role Create a role with single rule.\n rolebinding Create a RoleBinding for a particular Role or ClusterRole\n secret Create a secret using specified subcommand\n service Create a service using specified subcommand.\n serviceaccount Create a service account with the specified name<\/code><\/pre>\n\n\n\n
Lets create a deployment<\/p>\n\n\n\n
k create deploy bbdeploy --image=busybox --dry-run=true -o yaml<\/code><\/pre>\n\n\n\n
k get pods --show-labels\nNAME READY STATUS RESTARTS AGE LABELS\ndeploy-nginx-deploy-6d45895bf5-mv9wr 1\/1 Running 0 21s app=nginx-webserver-pod,pod-template-hash=6d45895bf5\ndeploy-nginx-deploy-6d45895bf5-vpt6p 1\/1 Running 0 21s app=nginx-webserver-pod,pod-template-hash=6d45895bf5<\/code><\/pre>\n\n\n\n
k get deploy --show-labels\nNAME READY UP-TO-DATE AVAILABLE AGE LABELS\ndeploy-nginx-deploy 2\/2 2 2 32s app=nginx-webserver<\/code><\/pre>\n\n\n\n
Scaling to 3<\/p><\/blockquote><\/figure>\n\n\n\n
> k scale --replicas=3 deploy\/deploy-nginx-deploy\ndeployment.apps\/deploy-nginx-deploy scaled<\/code><\/pre>\n\n\n\n
k get all\nNAME READY STATUS RESTARTS AGE\npod\/deploy-nginx-deploy-6d45895bf5-79kd7 0\/1 ContainerCreating 0 4s\npod\/deploy-nginx-deploy-6d45895bf5-mv9wr 1\/1 Running 0 5m\npod\/deploy-nginx-deploy-6d45895bf5-vpt6p 1\/1 Running 0 5<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
I have been working on Kubernetes cluster and will soon plan to give a Kubernetes Certified Developer exam. In my quest, I will just record some commands that I found helpful or useful in this blog. It may be multi-part, as I will keep adding on a daily basis the commands that I will be […]<\/p>\n","protected":false},"author":2,"featured_media":1006,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"image","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[34],"tags":[105],"class_list":["post-1003","post","type-post","status-publish","format-image","has-post-thumbnail","hentry","category-technical","tag-plaground","post_format-post-format-image"],"_links":{"self":[{"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/posts\/1003","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/comments?post=1003"}],"version-history":[{"count":0,"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/posts\/1003\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/media\/1006"}],"wp:attachment":[{"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/media?parent=1003"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/categories?post=1003"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.samarthya.me\/wps\/wp-json\/wp\/v2\/tags?post=1003"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}