Getting started

Basic terms: system parts

• Kubernetes: the whole orchestration system (K8s "k-eights" or Kube for short)

• Kubectl: CLI to configure Kubernetes and manage apps (using "cube control" official pronunciation)

• Node: single server in the Kubernetes cluster

• Kubelet: Kubernetes agent running on nodes

• Control plane: set of containers that manage the cluster

  • Includes API server, scheduler, controller manager, etcd and more

  • Sometimes called the "master"

Installing Kubernetes locally

• Kubernetes is a series of containers, CLI's and configurations

• Many ways to install:

  • MacOS: Docker Desktop - Enable in Settings. Sets up everything inside Docker's existing Linux VM

    • Runs, configures Kubernetes Master containers

    • Manages kubectl install and certificates

    • Easily install, disable and remove from Docker GUI

  • Docker Toolbox on Windows - MiniKube. Uses VirtualBox to make Linux VM

    • Doesn't install kubectl, has to be installed separately

  • Your own Linux host or VM - MicroK8s. Installs Kubernetes right on the OS

    • Uses snap (rather apt or yum) for install.

    • Control MicroK8s service via microk8s. commands

    • kubectl accessible via microk8s.kubectl

    • Add an alias to your shell (.bash_profile): alias kubectl=microk8s.kubectl

• Kuberneters in a Browser

  • http://play-with-k8s.com

  • katacoda.com

Kubernetes Container Abstractions

• Pod: one or more containers running together on one node. Basic unit of deployment. Containers are always in pods.

• Controller: for creating / updating pods and other objects. Controllers manage pods, you almost never manage pods yourself. There are many types of Controllers, including Deployment, ReplicaSet, StatefulSet, DaemonSet, Job, CronJob, etc.

• Service: network endpoint to connect to a pod.

• Namespace: Filtered group of objects in cluster.

• Secrets, ConfigMaps, etc.

Kubernetes Run, Create and Apply

• Kubernetes is evolving, and so is the CLI

• We get 3 ways to create pods from the kubectl CLI

• kubectl run (changing to be only for pod creation)

• kubectl create (create some resources via CLI or YAML)

• kubectl apply (create / update anything via YAML)

Basic commands

• kubectl version - shows a version of Client and Server

• kubectl cluster-info

• kubectl run my-nginx --image nginx - this will create a pod, replica set and a deployment

• kubectl get pods - get current pods

• kubectl get all - get all components

• kubectl delete deployment my-nginx - delete named deployment

Scaling ReplicaSets

• Start new deployment for one replica/pod

  kubectl run my-apache --image httpd

• Scale deployment

  kubectl scale deploy/my-apache --replicas 2

  kubectl scale deployment my-apache --replicas 2 (these are same commands)

Inspecting Deployments

• Get logs

  kubectl logs deployment my-apache

• Get logs from pods with a given label

  kubectl logs -l run=my-apache

• Stern for Kubernetes can be used to tail logs from multiple pods (https://github.com/wercker/stern)

  brew install stern

  stern pod-query

• Get pod info

  kubectl describe pod/<pod-id> (pod-id can be obtained with kubectl get pods)`