[k8s] Environment Variable
=============
###### tags: `kubernetes` `application lifecycle management`

> create data, inject into Pod

## types of `valueFrom`
+ fieldRef

    env:
    - name: MY_POD_NAME
      valueFrom:
        fieldRef:
          fieldPath: metadata.name

+ configMapKeyRef
+ secretKeyRef
+ resourceFieldRef

    env:
    - name: MY_CPU_REQUEST
      valueFrom:
        resourceFieldRef:
          containerName: test-container
          resource: requests.cpu

## ConfigMap

# imperative way
kubectl create configmap app-config \
--from-literal=APP_COLOR=blue \
--from-literal=APP_MODE=prod

# declarative way
apiVersion: v1
kind: ConfigMap
metadata: 
  name: app-config
data:
  APP_COLOR: blue
  APP_MODE: prod



## Secret
> + Secrets are not encrypted. Only encoded.
> + Configure least-privilege access to Secrets -RBAC
> + Consider 3rd secrets store providers
> + AWS provider, Azure provider, GCP provider, Vault provider

kubectl create secret generic app-secret \
--from-literal=DB_HOST=mysql \
--from-literal=DB_PASSWORD=passwrd

apkVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  DB_HOST: mysql
  DB_USER: root
  DB_PASSWORD: passwrd