03-state-config-and-jobs.md

Lab Guide - State, config and jobs

Exercise 1 - State Persistance

The Kubernetes Volume is simply a directory on disk mapped to the pod that allows you to store and share data usually beyond the lifetime of a pod.

Mounting emptyDir

1. Create busyboxvol pod with two containers (c1 and c2), each one will have the image busybox and will run the 'sleep 3600' command. Make both containers mount an emptyDir at '/etc/foo'.

   # review the manifest file - look how Volume and Volume mounts are performed
   cat ./assets/lab-03/state-emptyDir.yaml
   
   # Create Pod from the script file
   kubectl apply -f ./assets/lab-03/state-emptyDir.yaml

2. Connect to the first container c1 , write current date time in the file /etc/foo/mydata.txt

   kubectl exec -it busyboxvol -c c1 -- /bin/sh
   ls /etc/foo/ # confirm dir is empty
   echo $(date) > /etc/foo/mydata.txt
   cat /etc/foo/mydata.txt # confirm that stuff has been written successfully
   exit

   Notice /etc/foo/ directory has been mounted onto the container

3. Connect to the second container c2 and read /etc/foo/mydata.txt file to standard output.

   kubectl exec -it busyboxvol -c c2 -- /bin/sh
   cat /etc/foo/mydata.txt
   exit

   Notice that two containers within pod busyboxvol share the directory

Storage Classes

1. List all the storage class available on your cluster

   kubectl get sc

2. Create a PersistentVolumeClaim for azure storage class default, called mypvc, a request of 1Gi with an access mode of ReadWriteOnce.

   # review the manifest and look how PersistentVolumeClaim is written
   cat ./assets/lab-03/state-mypvc.yaml
   
   # create PersistentVolumeClaim from the script file
   kubectl apply -f ./assets/lab-03/state-mypvc.yaml

3. Show the PersistentVolumes and PersistentVolumeClaims of the cluster

   # creation can take time, press ctrl+c to exit watch loop once pv and pvc are created
   kubectl get pv
   kubectl get pvc -w

4. Create a nginxvol pod running nginx image and Mount the PersistentVolumeClaim to '/etc/foo'.

   # review the manifest and look how Volume and Volume mounts are performed
   cat ./assets/lab-03/state-mount-pvc.yaml
   
   # Create Pod from the script file
   kubectl apply -f ./assets/lab-03/state-mount-pvc.yaml

5. Connect to the 'nginxvol' pod, and copy the '/etc/passwd' file to '/etc/foo'

   kubectl exec nginxvol -it -- cp /etc/passwd /etc/foo/passwd
   kubectl exec nginxvol -it -- cat /etc/foo/passwd

6. Delete nginxvol pod

   kubectl delete po nginxvol

7. Recreate nginxvol pod running nginx image and Mount the PersistentVolumeClaim to '/etc/foo'.

   # create Pod from the script file
   kubectl apply -f ./assets/lab-03/state-mount-pvc.yaml

8. Connect to the 'nginxvol' pod, and list all files in '/etc/foo'

   kubectl exec nginxvol -it -- ls /etc/foo
   kubectl exec nginxvol -it -- cat /etc/foo/passwd

   Notice files persisted, even after pod was deleted and recreated.

Exercise 2 - Config and Secrets

Steps

1. Create a configmap named myconfig with values foo=lala,foo2=lolo

   kubectl create configmap myconfig --from-literal=foo=lala --from-literal=foo2=lolo

2. Create a secret called mysecret with the values password=mypass

   kubectl create secret generic mysecret --from-literal=password=mypass

3. Create a new nginx pod that loads the value from configmap myconfig -> foo in an env variable called 'option'. Also load secret 'mysecret' as a volume inside an nginx pod on path /etc/secrets.

   # review the manifest and look how the configMap and secret is referenced
   cat ./assets/lab-03/state-configs.yaml
   
   # Create Pod from the script file
   kubectl apply -f ./assets/lab-03/state-configs.yaml

4. Check environment variable option and /etc/secrets has expected values

   kubectl exec -it nginx -- env | grep option
   kubectl exec -it nginx -- ls /etc/secrets

Exercise 3 - Jobs

Steps

1. Create CronJob called sleepycron that runs pod busy box with sleep 5 command every minute

   kubectl create ns my-cron-job
   kubectl create cronjob sleepycron --image=busybox -n my-cron-job --schedule "*/1 * * * *" -- sleep 5

2. List all the CronJob, Jobs and Pods

   kubectl get cj,job,pod
   # observe every minute job and pods will be created