Kubernetes#

TODO#

  • [ ] StatefulSet

Kubernetes Architecture#

Control Plane

  • api

  • sched

  • etcd

  • c-m Control Manager

  • c-c-m Cloud Control Manager (optional)

Node

  • kubectl

  • kproxy

Draft#

kubectl [command] [type] [name] [flags]

kubectl get pod app -o yaml

Objects can be created imperatively or declaratively.

Imperative approach

kubectl run nginx --image=nginx --restart=Never --port=80

Declarative approach

nginx-pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: frontend
spec:
  containers:
    - name: frontend
      image: nginx
      ports:
        - containerPort: 80
  restartPolicy: Never

kubectl create -f nginx-pod.yaml

  • create command instantiates a new object, if executed for existing object will result in an error.

  • apply command meant to update an existing object fully or incrementally. If object doesn’t exist it behaves same as create.

#

Service#

  • A Service is a method for exposing a network application that is running as one or more pods in your cluster.

  • The Servie API, part of Kubernetes, is an abstraction to help you expose groups of Pods over a network.

  • selector determines the set pods targeted by a Service.

Tips for CKAD#

kubectl config set-context <context> --namespace=<namespace>

How to’s#

Load docker images to kind nodes#

kind doesn’t use local docker images and will try to fetch from the container registry. Local images can be loaded using:

kind load docker-image nginx --name kind-cluster-name

Using kind behind proxy#

As kind doesn’t use local docker images

export http_proxy=http://...
export https_proxy=http://...

kind create cluster --config ...

Using Git Bash on Windows#

This stops Git Bash from altering file system paths.

export MSYS_NO_PATHCONV=1

Ref