kubectl cheatsheet #kubernetes

kubectl_cheatsheet.md

• Label:

  • Labels are key/value pairs that are attached to objects, such as pods.
  • Labels can be attached to objects at creation time and subsequently added and modified at any time.
  • Each object can have a set of key/value labels defined. Each Key must be unique for a given object.

• Service:

  • A Kubernetes Service is an abstraction which defines a logical set of Pods and a policy by which to access them - sometimes called a micro-service.
  • Behind a service, pods come and go with autoscaling but service is by which we communicate.

• Namespace:

  • Within Namespaces level we can apply resource limits.
  • Most Kubernetes resources (e.g. pods, services, replication controllers, and others) are in some namespaces.
  • However namespace resources are not themselves in a namespace.
  • And low-level resources, such as nodes and persistentVolumes, are not in any namespace.
  • Service endpoint created has dns entry of form <service-name>.<namespace-name>.svc.cluster.local.
    • So with namespace we can have similar services across multiple namespaces such as Development, Staging and Production

• Get components(etcd, scheduler ...) status : kubectl get cs

Node

• Get all nodes in cluster : kubectl get no
• Watch nodes continuously: kubectl get nodes -w

Pods

• Get pods running: kubectl get po
• Get pods with labels : kubectl get pods --show-labels
• Select pods with specific label : kubectl get pod -l class
• Get non-running pods: kubectl get pods --field-selector=status.phase!=Running
  • Get only running pods: kubectl get po --field-selector status.phase=Running
  • #Ref : https://kubernetes.io/docs/concepts/overview/working-with-objects/field-selectors/
• Grep pod with specific name : kubectl delete pod $(kubectl get pods --no-headers | grep "pod-name" | awk '{ print 0 }')
  • Little bash fun up ther^, if you know exact name use: kubectl delete pod pod-name
• Get pods not running in 'non-default' namespace: kubectl get services --field-selector metadata.namespace!=default
• Kubec

Services

• Get all running services: kubectl get svc

Cluster

• Get all namespaces: kubectl get namespaces
• Get cluster info: kubectl cluster-info
• Get all contexts: kubectl config get-contexts
• More details on namespaces: https://gist.github.com/42e7be266195f8711ec59814d4db5b1e

Kubectl

• Kubectl output with custom field and sorted:

  • kubectl get pod --sort-by .status.containerStatuses[].restartCount -o custom-columns=Name:.metadata.name,restartCount:.status.containerStatuses[].restartCount

• Kubectl output filter with selected field

  • #Ref : https://kubernetes.io/docs/concepts/overview/working-with-objects/field-selectors/`
  • kubectl get services --field-selector metadata.namespace!=default
  • kubectl get po --field-selector status.phase=Running

• Via a label selector, the client/user can identify a set of objects. The label selector is the core grouping primitive in Kubernetes.