[k8s] ConfigMap

tags: kubernetes application lifecycle management

• [k8s] ConfigMap
• 1⃣ ConfigMap 特性
• ⭐ ConfigMaps are used as environment variables
  • 🔆 how to create
    • from property file
    • from literal value
    • from yaml
  • 🔆 how to use
    • fetch value of specific key
    • fetch values of all keys
• ⭐ ConfigMaps are used as files
  • 🔆 how to create
    • from yaml
  • 🔆 how to use
• resource

1⃣ ConfigMap 特性

ConfigMap 通常都是用來存放偏向部署面的設定檔，像是資料庫的初始化設定、nginx 設定檔等等

# game.properties
enemies=aliens
lives=3
enemies.cheat=true
enemies.cheat.level=noGoodRotten
secret.code.passphrase=UUDDLRLRBABAS
secret.code.allowed=true
secret.code.lives=30

# ui.properties
color.good=purple
color.bad=yellow
allow.textmode=true
how.nice.to.look=fairlyNice

⭐ ConfigMaps are used as environment variables

🔆 how to create

from property file

kubectl create configmap game-config \
--from-file=./game.properties \
--from-file=./ui.properties \
-n playground

from literal value

kubectl create configmap special-config \
--from-literal=special.how=very \
--from-literal=special.type=charm \
-n playground

from yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: special-config
  namespace: default
data:
  special.how: very
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: env-config
  namespace: default
data:
  LOG_LEVEL: INFO
  SPECIAL_LEVEL: very
  SPECIAL_TYPE: charm

kubectl get configmap -n playground
kubectl describe configmap game-config -n playground
kubectl delete configmap game-config -n playground

🔆 how to use

fetch value of specific key

apiVersion: v1
kind: Pod
metadata:
  namespace: playground
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: k8s.gcr.io/busybox
      command: [ "/bin/sh", "-c", "env" ]
      env:
        - name: SPECIAL_LEVEL_KEY
          valueFrom:
            configMapKeyRef:
              name: special-config
              key: special.how

fetch values of all keys

apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: k8s.gcr.io/busybox
      command: [ "/bin/sh", "-c", "env" ]
      envFrom:
      - configMapRef:
          name: special-config

⭐ ConfigMaps are used as files

🔆 how to create

from yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: mosquitto-config-file
data:
  mosquitto.conf: |
    log_des stdout
    log_type all
    log_timestamp true
    listener 9001

🔆 how to use

1. volumes mounted into the pod
2. mount volumes into container

apiVersion: v1
kind: Pod
metadata:
  name: mosquitto
spec:
  containers:
    - name: mosquitto
      image: eclipse-mosquitto:1.6.2
      ports:
        - containerPort: 1883
      volumeMounts:
        - name: mosquitto-config
          mountPath: /mosquitto/config
  volumes:
    - name: mosquitto-config
      configMap:
        name: mosquitto-config-file

resource

• Kubernetes 那些事 — ConfigMap 與 Secrets