Kubernetes 101

https://kubernetes.io/docs/user-guide/walkthrough/
This is my self-learning notes for Kubernetes 101.
"For Kubernetes 101, we will cover kubectl, pods, volumes, and multiple containers."

Commands

kubectl create -f pod-nginx.yaml
kubectl get pod
kubectl describe pods/nginx

Create a POD

1. Pod definition for pod-nginx.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.7.9
    ports:
    - containerPort: 80

2. Create pod on your cluster

kubectl create -f pod-nginx.yaml
root@elx744647vq:/home/elluffn/k8s# kubectl get pod
NAME      READY     STATUS    RESTARTS   AGE
nginx     1/1       Running   0          2d
root@elx744647vq:/home/elluffn/k8s# 

3. Get pods

root@elx744647vq:/home/elluffn/k8s# kubectl get pod
NAME      READY     STATUS    RESTARTS   AGE
nginx     1/1       Running   0          2d

4. Describe a pod

root@elx744647vq:/home/elluffn/k8s# kubectl describe pods/nginx
Name:         nginx
Namespace:    default
Node:         elx744647vq/146.11.23.8
Start Time:   Tue, 17 Oct 2017 17:09:57 +0800
Labels:       <none>
Annotations:  <none>
Status:       Running
IP:           10.244.0.19
Containers:
  nginx:
    Container ID:   docker://8f9f7f682002716b01c39a39def5c77984934c1727e0e675bab83e87c4846d17
    Image:          nginx:1.7.9
    Image ID:       docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451
    Port:           80/TCP
    State:          Running
      Started:      Tue, 17 Oct 2017 17:14:31 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-9sqlp (ro)
Conditions:
  Type           Status
  Initialized    True 
  Ready          True 
  PodScheduled   True 
Volumes:
  default-token-9sqlp:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-9sqlp
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.alpha.kubernetes.io/notReady:NoExecute for 300s
                 node.alpha.kubernetes.io/unreachable:NoExecute for 300s
Events:          <none>
root@elx744647vq:/home/elluffn/k8s# 

Get a shell to a container

https://kubernetes.io/docs/tasks/debug-application-cluster/get-shell-running-container/

root@elx744647vq:/home/elluffn/k8s# kubectl help exec
Execute a command in a container.

Examples:
  # Get output from running 'date' from pod 123456-7890, using the first container by default
  kubectl exec 123456-7890 date
  
  # Get output from running 'date' in ruby-container from pod 123456-7890
  kubectl exec 123456-7890 -c ruby-container date
  
  # Switch to raw terminal mode, sends stdin to 'bash' in ruby-container from pod 123456-7890
  # and sends stdout/stderr from 'bash' back to the client
  kubectl exec 123456-7890 -c ruby-container -i -t -- bash -il
  
  # List contents of /usr from the first container of pod 123456-7890 and sort by modification time.
  # If the command you want to execute in the pod has any flags in common (e.g. -i),
  # you must use two dashes (--) to separate your command's flags/arguments.
  # Also note, do not surround your command and its flags/arguments with quotes
  # unless that is how you would execute it normally (i.e., do ls -t /usr, not "ls -t /usr").
  kubectl exec 123456-7890 -i -t -- ls -t /usr

Options:
  -c, --container='': Container name. If omitted, the first container in the pod will be chosen
  -p, --pod='': Pod name
  -i, --stdin=false: Pass stdin to the container
  -t, --tty=false: Stdin is a TTY

Usage:
  kubectl exec POD [-c CONTAINER] -- COMMAND [args...] [options]

Use "kubectl options" for a list of global command-line options (applies to all commands).
root@elx744647vq:/home/elluffn/k8s# kubectl exec nginx date
Thu Oct 19 09:44:08 UTC 2017
root@elx744647vq:/home/elluffn/k8s# 

Create a busybox container via kubectl

$ kubectl run busybox --image=busybox --restart=Never --tty -i --generator=run-pod/v1 --env "POD_IP=$(kubectl get pod nginx -o go-template='{{.status.podIP}}')"
u@busybox$ wget -qO- http://$POD_IP # Run in the busybox container
u@busybox$ exit # Exit the busybox container
$ kubectl delete pod busybox # Clean up the pod we created with "kubectl run"