Environment Variables in Kubernetes

Question : There are a number of parameters that are used by applications. We need to define these as environment variables so that we can use them as needed within different configs. Below is a scenario which needs to be configured on Kubernetes cluster. Please find below more details about it.

Create a namespace named as fieldref-namespace.

Create a pod named envars-fieldref under the namespace fieldref-namespace.

Configure spec as the container name should be fieldref-container, use image httpd preferable latest tag, use command 'sh', '-c' and args should be

'while true; do echo -en '/n'; printenv NODE_NAME POD_NAME POD_NAMESPACE; printenv POD_IP POD_SERVICE_ACCOUNT; sleep 10; done;'

(Note: please take care of indentations)

Define five environment variables as mentioned below:

a.) The first env should be named as NODE_NAME, set valueFrom fieldref and fieldPath should be spec.nodeName.

b.) The second env should be named as POD_NAME, set valueFrom fieldref and fieldPath should be metadata.name.

c.) The third env should be named as POD_NAMESPACE, set valueFrom fieldref and fieldPath should be metadata.namespace.

d.) The fourth env should be named as POD_IP, set valueFrom fieldref and fieldPath should be status.podIP.

e.) The fifth env should be named as POD_SERVICE_ACCOUNT, set valueFrom fieldref and fieldPath shoulbe be spec.serviceAccountName.

Set restart policy to Never.

To check the output, exec the pod and use printenv command.

Note: The kubectl utility on jump_host has been configured to work with the kubernetes cluster.

Please Note :-  Perform the below commands based on your question  server,  user name & other details might differ . So please read task carefully before executing. All the Best 👍

Solution:  

1. At first  kubectl  utility configure and working from jump server, run below commands   

thor@jump_host /$ kubectl get namespace NAME              STATUS   AGE default           Active   2m15s kube-node-lease   Active   2m19s kube-public       Active   2m19s kube-system       Active   2m20s thor@jump_host /$ thor@jump_host /$ kubectl get pods No resources found in default namespace. thor@jump_host /$

2.  Create namespace as per the task       

thor@jump_host /$ kubectl create namespace fieldref-namespace namespace/fieldref-namespace created thor@jump_host /$ thor@jump_host /$ kubectl get namespace NAME                 STATUS   AGE default              Active   2m59s fieldref-namespace   Active   5s kube-node-lease      Active   3m3s kube-public          Active   3m3s kube-system          Active   3m4s thor@jump_host /$

3.  Create yaml  file with all the parameters , you can copy form gitlab

    https://gitlab.com/nb-tech-support/devops.git

    ( Refer Below Video for more clarity ) 

thor@jump_host /$ vi /tmp/envars.yml thor@jump_host /$ cat /tmp/envars.yml apiVersion: v1 kind: Pod metadata:   name: envars-fieldref   namespace: fieldref-namespace spec:   restartPolicy: Never   containers:     - name: fieldref-container       image: httpd:latest       command: ["sh", "-c"]       args:         - while true; do           echo -en '\n';           printenv NODE_NAME POD_NAME POD_NAMESPACE;           printenv POD_IP POD_SERVICE_ACCOUNT;           sleep 10;           done;       env:         - name: NODE_NAME           valueFrom:             fieldRef:               fieldPath: spec.nodeName         - name: POD_NAME           valueFrom:             fieldRef:               fieldPath: metadata.name         - name: POD_NAMESPACE           valueFrom:             fieldRef:               fieldPath: metadata.namespace         - name: POD_IP           valueFrom:             fieldRef:               fieldPath: status.podIP         - name: POD_SERVICE_ACCOUNT           valueFrom:             fieldRef:               fieldPath: spec.serviceAccountName thor@jump_host /$

 4.  Run below command to create pod   

thor@jump_host /$ kubectl create -f /tmp/envars.yml pod/envars-fieldref created thor@jump_host /$

5. wait for the pod running status

thor@jump_host /$ kubectl get pods -n fieldref-namespace NAME              READY   STATUS    RESTARTS   AGE envars-fieldref   1/1     Running   0          15s thor@jump_host /$

6. Validate the task by login on pod and run printenv

      

thor@jump_host /$ kubectl exec -it envars-fieldref  -n fieldref-namespace  -- /bin/bash root@envars-fieldref:/usr/local/apache2# printenv KUBERNETES_SERVICE_PORT_HTTPS=443 KUBERNETES_SERVICE_PORT=443 HOSTNAME=envars-fieldref POD_NAME=envars-fieldref POD_NAMESPACE=fieldref-namespace PWD=/usr/local/apache2 HTTPD_VERSION=2.4.48 HOME=/root KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443 HTTPD_PATCHES= TERM=xterm NODE_NAME=node01 HTTPD_SHA256=1bc826e7b2e88108c7e4bf43c026636f77a41d849cfb667aa7b5c0b86dbf966c SHLVL=1 KUBERNETES_PORT_443_TCP_PROTO=tcp KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1 POD_IP=10.244.1.2 KUBERNETES_SERVICE_HOST=10.96.0.1 KUBERNETES_PORT=tcp://10.96.0.1:443 KUBERNETES_PORT_443_TCP_PORT=443 PATH=/usr/local/apache2/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin POD_SERVICE_ACCOUNT=default HTTPD_PREFIX=/usr/local/apache2 _=/usr/bin/printenv root@envars-fieldref:/usr/local/apache2#

7.  Click on Finish & Confirm to complete the task successful

Happy Learning!!!!

Apart from this if you need more clarity,  I have made a  tutorial video on this , 

please go through and share your comments. Like and share the knowledge