Assume that you want to build a ReplicaSet resource. To accomplish so, you would determine the ReplicaSet in a file named replicaset.yaml file, and then pass the following command:<\/p>\n\n\n\n
<strong>$ kubectl create -f replicaset.yaml<\/strong><\/pre>\n\n\n\nCertainly, this builds your ReplicaSet in Kubernetes. But what goes on behind the scenes?<\/p>\n\n\n\n
Kubernetes includes a create ReplicaSet operation, and like other Kubernetes operations, it is brought to light as an API endpoint. The exact API endpoint for this operation is:
POST \/apis\/apps\/v1\/namespaces\/{namespace}\/replicasets<\/pre>\n\n\n\nYou can locate the API endpoints of all Kubernetes\u2019 operations in the API reference, comprising the above-mentioned endpoint. To create a definite request to an endpoint, you require to pre-pend the URL of the API server to the endpoint paths that are mentioned in the API reference.<\/p>\n\n\n\n
When you run the above command, kubectl initiates an HTTP POST request to the above API endpoint. The ReplicaSet definition (which you added in the replicaset.yaml file) is passed in the request’s body. This is how kubectl functions for all commands that connect with the Kubernetes cluster. In all these instances, kubectl only makes HTTP requests to the relevant Kubernetes API endpoints. Note that it\u2019s entirely possible to control Kubernetes with a tool such as curl by manually issuing HTTP requests to the Kubernetes API. Kubectl simply makes it simpler for you to utilise the Kubernetes API. These are the fundamentals of what kubectl is and how it works.<\/p>\n\n\n\n
Kubectl Commands<\/h2>\n\n\n\n The kubectl command-line utility is a mighty tool, and let\u2019s go through the basic kubectl commands that apply to all Kubernetes objects.<\/p>\n\n\n\n1. Cluster Management<\/h3>\n\n\n\n A Kubernetes cluster is a collection of nodes that execute containerized applications. It lets containers run across several machines and environments: cloud-based, virtual, on-premises and physical. Listed below are the kubectl commands that can be utilised to manage a cluster.<\/p>\n\n\n\n
kubectl cluster-infokubectl version<\/strong>kubectl config view<\/strong>kubectl api-resources<\/strong>kubectl api-versions<\/strong>kubectl get all –all-namespaces<\/strong>2. Namespaces<\/h3>\n\n\n\n Shortcode = ns<\/p>\n\n\n\n
kubectl create namespace <namespace_name><\/strong>kubectl get namespace <namespace_name><\/strong>kubectl describe namespace <namespace_name><\/strong>kubectl delete namespace <namespace_name><\/strong>kubectl edit namespace <namespace_name><\/strong>kubectl top namespace <namespace_name><\/strong>3. Node operations<\/h3>\n\n\n\n A Node is a worker machine in Kubernetes and can either be a virtual or a physical machine, which depends on the cluster. Every Node is handled by the control plane. A Node can contain several pods, and the Kubernetes control plane handles scheduling the pods automatically across the Nodes in the cluster. The following commands can be utilised for Node Operations.<\/p>\n\n\n\n
kubectl taint node <node_name><\/strong>kubectl get node<\/strong>kubectl delete node <node_name><\/strong>kubectl top node<\/strong>kubectl describe nodes | grep Allocated -A 5<\/strong>kubectl get pods -o wide | grep <node_name><\/strong>kubectl annotate node <node_name><\/strong>kubectl cordon node <node_name><\/strong>kubectl uncordon node <node_name><\/strong>kubectl drain node <node_name><\/strong>kubectl label node4. Listing Resources <\/span><\/h3>\n\n\n\nKubernetes resources are also regarded as Kubernetes objects related to a certain namespace, you can either utilise individual Kubectl get commands to jot down every resource one by one, or you can jot down all the resources in a Kubernetes namespace by executing a single command. Mentioned below is the list of commands to get the resource information.<\/p>\n\n\n\n
kubectl get namespaces<\/strong>kubectl get pods<\/strong>kubectl get pods -o wide<\/strong>kubectl get pods\u2013field-selector=spec. nodeName=[server-name]<\/strong>kubectl get replicationcontroller [replication-controller-name]<\/strong>kubectl get replicationcontroller, services<\/strong>5. Daemonsets <\/span><\/h3>\n\n\n\nA Daemonset assures that some or all\u00a0 Nodes run a copy of a Pod. As nodes are incorporated into the cluster, Pods are implemented to them. As nodes are erased from the cluster, those Pods are garbage collected. Erasing a DaemonSet will clean up the Pods it created.<\/p>\n\n\n\n
kubectl get daemonset<\/strong>kubectl edit daemonset <daemonset_name><\/strong>kubectl delete daemonset <daemonset_name>kubectl create daemonset <daemonset_name><\/strong>kubectl rollout daemonset<\/strong>kubectl describe ds <daemonset_name> -n <namespace_name><\/strong>6. Events<\/h3>\n\n\n\n Shortcode = ev<\/p>\n\n\n\n
Kubernetes events are objects that display what is happening within a cluster, like what decisions were implemented by the scheduler or why some pods were erased from the node. Events are the first thing to look at for application, along with infrastructure operations when something is not functioning as anticipated. Mentioned below are the Kubectl commands to get the events.
kubectl get events<\/strong>kubectl get events –field-selector type=Warning<\/strong>kubectl get events –field-selector involvedObject.kind!=Pod<\/strong>kubectl get events –field-selector involvedObject.kind=Node, involvedObject.name=<node_name><\/strong>kubectl get events –field-selector type!=Normal<\/strong>7. Logs<\/h3>\n\n\n\n You can use Kubernetes logs commands to monitor, log and debug the pods<\/p>\n\n\n\n
kubectl logs <pod_name><\/strong>kubectl logs –since=1h <pod_name><\/strong>kubectl logs –tail=20 <pod_name><\/strong>kubectl logs -f <service_name> [-c <$container>]<\/strong>kubectl logs -f <pod_name><\/strong>kubectl logs -c <container_name> <pod_name><\/strong>kubectl logs <pod_name> pod.log<\/strong>kubectl logs –previous <pod_name><\/strong>8. Deployments<\/h3>\n\n\n\n Shortcode = deploy.<\/p>\n\n\n\n
A Kubernetes Deployment is utilised to inform Kubernetes how to design or change instances of the pods that hold a containerized application. Deployments can enhance the number of replica pods, enable the rollout of revised code in a controlled way, or roll back to an earlier deployment version if required.<\/p>\n\n\n\n
kubectl get deployment<\/strong>kubectl describe deployment <deployment_name><\/strong>kubectl edit deployment <deployment_name><\/strong>kubectl create deployment <deployment_name>kubectl delete deployment <deployment_name>\u00a0kubectl rollout status deployment <deployment_name><\/strong>9. Replication Controllers<\/h3>\n\n\n\n Shortcode = rc<\/p>\n\n\n\n
kubectl get rc<\/strong>kubectl get rc –namespace=\u201d<namespace_name>\u201d<\/strong>\u00a010. ReplicaSets<\/h3>\n\n\n\n Shortcode = rs<\/p>\n\n\n\n
kubectl get replicasets<\/strong>kubectl describe replicasets <replicaset_name><\/strong>kubectl scale –replicas=[x]<\/strong>11. Secrets<\/h3>\n\n\n\n A Kubernetes Secret is an object that comprises a minor portion of sensitive data like a token, a key or a password. Such data might otherwise be inserted in an image or in a Pod specification. Users can build Secrets and the system also generates a few Secrets with the help of the following Kubectl commands.<\/p>\n\n\n\n
kubectl create secret<\/strong>kubectl get secrets<\/strong>kubectl describe secrets<\/strong>kubectldelete secret <secret_name><\/strong>12. Services and Service Accounts: <\/span><\/h3>\n\n\n\nA Kubernetes service is a logical abstraction for a deployed group of pods in a cluster (which all perform the same function) and Service accounts are used to provide an identity for pods. Pods that want to interact with the API server will authenticate with a particular service account.<\/p>\n\n\n\n
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![\"Kubectl\"](\"https:\/\/www.interviewbit.com\/blog\/wp-content\/uploads\/2022\/04\/Kubectl-923x1024.png\")
<\/figure>\n\n\n\n![\"Kubectl1\"](\"https:\/\/www.interviewbit.com\/blog\/wp-content\/uploads\/2022\/04\/Kubectl1-1024x514.png\")
<\/figure>\n\n\n\n![\"What](\"https:\/\/www.interviewbit.com\/blog\/wp-content\/uploads\/2022\/04\/What-is-Kubernetes-1024x690.png\")
<\/figure>\n\n\n\n![\"Kubectl](\"https:\/\/www.interviewbit.com\/blog\/wp-content\/uploads\/2022\/04\/Kubectl-Command-1024x295.png\")
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