microk8s.txt

#Microk8s website
microk8s.io

#Terms
 - Node = kubernets master computer contols nodes, nodes do the work of running container pods
 - Namespace = groups of kubernetes objects, default namespace is called "default", used for organization
 - Pod = one or more containers running together to provide service
 - ReplicaSet = two or more pods providing the service
 - Deployment = more advanced version of ReplicaSet, controls updating better
 - Service = configuration exposing a port for networking to an object 
 - NodePort - Pod can communicate with outside via port mapping
   - Valid NodePort Ranges are from 30,000 - 32,767	
 - ClusterIP - Pod gets an internal IP address
 - LoadBalancer - Used to distribute load of service to multiple pods
 - Job - runs a job within pod and finishes
 - CronJob - runs a job as a specific time

#To view snap versions of microk8s that are available to install on Ubuntu
snap info microk8s

#Using snap package to install latest stable version of Microk8s
sudo snap install microk8s --classic

#Using snap package to install specific version of Microk8s, such as 1.13
sudo snap install microk8s --classic --channel=1.13/stable

#If you want normal user to use microk8 commands without sudo
sudo usermod -a -G microk8s $USER

#Check the status of Microk8s
microk8s.status

#Enable kubernetes dashboard and kubedns services
microk8s.enable dashboard dns

microk8s.docker images

microk8s.inspect #tells you the state of the services
microk8s.reset #shuts down and restarts cluster



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Microk8s.kubectl 
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#Get information about the kubernetes cluster
microk8s.kubectl cluster-info

#List all nodes that make up Kubernetes cluster
#In Microk8s it should list just your computer
microk8s.kubectl get nodes

#List all nodes that make up Kubernetes cluster, with more parameters shown
microk8s.kubectl get nodes -o wide

#Get Kubernetes componets status
microk8s.kubectl get cs

#Get Services
microk8s.kubectl get svc

To view all objects within the default namespace, prefix with "watch" to view it live
microk8s.kubectl get all -o wide

#Check the deployment process, find IP address of dashboard, prefix with "watch" to view it live
microk8s.kubectl get all --all-namespaces

#Once you have IP address of dashboard, use https to access it, you will need a token
https://<IP ADDRESS>:443

#To get the token used to login to dashboard, run the following two commands
token=$(microk8s.kubectl -n kube-system get secret | grep default-token | cut -d " " -f1)
microk8s.kubectl -n kube-system describe secret $token

#To see events that are happening/happed run
microk8s.kubectl get events



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Microk8s.kubectl PODS
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#Create a pod for the nginx server,other examples include ansible, mongodb, redis, nodejs, etc
microk8s.kubectl run nginx --image nginx

#View the pods you have created
microk8s.kubectl get pods

#Get information about the pod, can pipe to less for reability
microk8s.kubectl describe pod nginx

#To delete the nginx pod
microk8s.kubectl delete pod nginx

#To delete all the pods
microk9s.kubectl delete pods --all


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Microk8s.kubectl DEPLOYMENTS
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#Create a deployment using Nginx
microk8s.kubectl create deployment nginx --image=nginx

#Set the deployment to autoscale between min and max replicas
microk8s.kubectl autoscale deployment nginx --min=3 --max=10

#Scale the nginx deployment to specific number of containers, rerun to change number
microk8s.kubectl scale deploy nginx --replicas=2

#View the deployment
microk8s.kubectl get deployments

#View the pods you are created with deployment
microk8s.kubectl get pods --show labels

#View the replica set you are created with this deployment
microk8s.kubectl get rs

#View the horizontal pod autoscale set you are created with this deployment
microk8s.kubectl get hpa

#Get information about the deployment, can pipe to less for reability
microk8s.kubectl describe deployment nginx

#Open local port 80 to deployment port 80 on nginx deployment
microk8s.kubectl expose deployment nginx --port 80 --target-port 80

#View exposed services 
microk8s.kubectl get services

#Delete the service
microk8s.kubectl delete service nginx

#Delete the deployment, will also delete pods
microk8s.kubectl delete deployment nginx

#Delete the horizontal pod autoscale set you are created with this deployment
microk8s.kubectl delete hpa nginx


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Microk8s.kubectl PODS FROM FILE
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#Create a file named ~/mypod.yaml and paste in the following:
apiVersion: v1
kind: Pod
metadata:
    name: nginx
spec:
    containers:
    - name: nginx
        image: nginx


#Run the configuration yaml file
microk8s.kubectl create -f ~/mypod.yaml


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Microk8s.kubectl DEPLOYEMENT FROM FILE
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#Create a file named ~/mydeployment.yaml and paste in the following
apiVersion: apps/v1
kind: Deployment
metadata:
    name: nginx
    labels:
        app: nginx
spec:
    replicas: 2
    selector:
        matchLabels:
            app: nginx
    template:
        metadata:
            labels:
                app: nginx
        spec:
            containers:
            - name: nginx
                image: nginx:1.15.4
                ports:
                - containerPort: 80


#Run the configuration yaml file
microk8s.kubectl create -f ~/mydeployment.yaml


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Microk8s.kubectl NAMESPACES
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#Get a list of namespaces
microk8s.kubectl get namespaces

#To get all the pods within the kube-system namespace
microk8s.kubectl --namespace kube-ctl get pods

#To create a new namespace
microk8s.kubectl create <new namespace>


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Microk8s.kubectl ADD/REMOVE NODES
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#Get a list of nodes
microk8s.kubectl get nodes

#To see all details of node
kubectl describe node <nodename> | less

#Two add more nodes, first install microk8s on second server
#On the server you want to be the master run
microk8s add-node

#The add-node command will print out join command, run that command on second node example of command:
microk8s join ip-172-31-20-243:25000/DDOkUupkmaBezNnMheTBqFYHLWINGDbf

#To remove a node, use the IP Address of node to remove
microk8s remove-node <IP ADDRESS>

#On the node that you want to leave the cluster run the command
microk8s leave


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Microk8s.kubectl NODE SELECTOR
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#Get a list of nodes with additional info columns
microk8s.kubectl get nodes -o wide

#Add label to node, will use label to spin up pods on nodes with these labels
microk8s.kubectl label node <node name> <label>=<value>

#To view the labels associated with a node
microk8s.kubectl get node <node name> --show-labels

#To remove a label from a node, use minus sign instead of equals
microk8s.kubectl label node <node name> <label>-

#Run a pod on a specific node with the label/value info
apiVersion: v1
kind: Pod
metadata:
    name: nginx
spec:
    containers:
    - name: nginx
        image: nginx
    nodeSelector
      <label>: "<value>"
      

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Microk8s.kubectl PERSISTENT HOSTPATH VOLUMES
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#ReclaimPolicy options are Retain, Recycle, Delete
#Access Modes are ReadWriteOnce (RWO), ReadWriteMany (RWM), and ReadOnly (RO) - pv and pvc must match
#HostPath creates filepath on the node of the pod that claims the storage
#Hostpath can cause problem if pods run on different hosts

#Create a persistent volume (pv) using Hostpath. This will create /mnt/kube on the node it is running on
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-hostpath
  labels:
    type: local
spec:
  storageClassName: manual
  persistentVolumeReclaimPolicy: Retain
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: /mnt/kube
    

#To view persistent volumes
microk8s.kubectl get pv


#Create/bind a claim (pvc) for some storage on the persistent volume above, links by storageClassName
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-hostpath
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

      
#Create a pod that uses the pvc
apiVersion: v1
kind: Pod
metadata:
    name: nginx
spec:
  volumes:
  - name: host-volume
    persistentVolumeClaim:
      claimName: pvc-hostpath
  containers:
  - name: nginx
        image: nginx
        volumeMounts:
        - name: host-volume
          mountPath: /path/on/pod
    nodeSelector:
      <label>: "<value>"
    
    



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Microk8s.kubectl PERSISTENT NFS VOLUMES
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#Create nfs share (/etc/exports) on server 192.168.1.2 at /var/nfs/kube
#Create a persistent volume (pv) using NFS to use nfs share
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-hostpath
  labels:
    type: nfs
spec:
  storageClassName: manual
  persistentVolumeReclaimPolicy: Retain
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteMany
  nfs
    server: "192.168.1.2"
    path: "/var/nfs/kube"