Day 19/40
Kubernetes configmap and secret
Video Link
@piyushsachdeva
Git Repository
My Git Repo
We will look at configMap an secret in Kubernetes concepts in this section.
It’s not a best practice to save env, key and value in yaml file of a workload such as pod yaml file.
Kubernetes Secrets and ConfigMaps separate the configuration of individual container instances from the container image, reducing overhead and adding flexibility.
Kubernetes has two types of objects that can inject configuration data into a container when it starts up.
Demo
Let’s see the below yaml file, there’s an env with name FIRSTNAME and value is Piyush:
kind: Pod
metadata:
name: myapp-pod
labels:
app.kubernetes.io/name: MyApp
spec:
containers:
– name: myapp-container
image: busybox:1.28
env:
– name: FIRSTNAME
value: “Piyush”
command: [‘sh’, ‘-c’, ‘echo The app is running! && sleep 3600′]
Let’s run and check the env inside the pod:
pod/myapp-pod created
root@localhost:~# kubectl get pod
NAME READY STATUS RESTARTS AGE
myapp-pod 1/1 Running 0 8s
root@localhost:~# kubectl exec -it myapp-pod — sh
/ # echo $FIRSTNAME
Piyush
Now, we are going to do it with different ways as mentioned, configMap.
Imperative:
configmap/app-cm created
root@localhost:~# kubectl get cm
NAME DATA AGE
app-cm 2 5s
kube-root-ca.crt 1 16d
root@localhost:~# kubectl describe cm app-cm
Name: app-cm
Namespace: default
Labels: <none>
Annotations: <none>
Data
====
FIRSTNAME:
—-
Piyush
NEXT:
—-
Sina
BinaryData
====
Then we need to inject to yaml file of our pod, and define specific block for each environment variable:
kind: Pod
metadata:
name: myapp-pod
labels:
app.kubernetes.io/name: MyApp
spec:
containers:
– name: myapp-container
image: busybox:1.28
env:
– name: firstName
valueFrom:
configMapKeyRef:
name: app-cm
key: FIRSTNAME
– name: next
valueFrom:
configMapKeyRef:
name: app-cm
key: NEXT
command: [‘sh’, ‘-c’, ‘echo The app is running! && sleep 3600′]
Let’s run and check:
pod/myapp-pod created
root@localhost:~# kubectl get pod
NAME READY STATUS RESTARTS AGE
myapp-pod 1/1 Running 0 36s
root@localhost:~# kubectl exec -it myapp-pod — sh
/ # echo $firstName
Piyush
/ # echo $next
Sina
/ #
Name: myapp-pod
…
Environment:
firstName: <set to the key ‘FIRSTNAME’ of config map ‘app-cm’> Optional: false
next: <set to the key ‘NEXT’ of config map ‘app-cm’> Optional: false
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-
…
Declarative:
Let’s create yaml file from dry-run option:
The yaml file would be below:
data:
FIRSTNAME: Piyush
NEXT: Sina
kind: ConfigMap
metadata:
creationTimestamp: null
name: app-cm
Sample for cm:
data:
FIRSTNAME: Piyush
NEXT: Sina
kind: ConfigMap
metadata:
creationTimestamp: null
name: app-cm
Sample for pod:
kind: Pod
metadata:
name: dapi-test-pod
spec:
containers:
– name: test-container
image: registry.k8s.io/busybox
command: [ “/bin/sh”, “-c”, “env” ]
envFrom:
– configMapRef:
name: app-cm
restartPolicy: Never
Let’s check:
NAME DATA AGE
configmap/app-cm 2 5m53s
configmap/kube-root-ca.crt 1 16d
NAME READY STATUS RESTARTS AGE
pod/dapi-test-pod 0/1 Completed 0 4m15s
Name: dapi-test-pod
…
Environment Variables from:
app-cm ConfigMap Optional: false…
Following this link for get information about secret.
(Will be updated soon!)
