K8S resource configuration management

1. Secret

Secret is a k8s resource used to store sensitive data such as passwords, tokens, keys, etc. Although this type of data can also be stored in Pods or mirrors, it is placed in Secret to more conveniently control how the data is used and reduce exposure. risk.

1. There are three types of Secrets

• kubernetes.io/service-account-token: automatically created by Kubernetes and used to access the APIServer's Secret. The Pod will use this Secret to communicate with the APIServer by default and will be automatically mounted to the Pod's /run/secrets/kubernetes.io/serviceaccount in the directory;
• Opaque: Secret in base64 encoding format, used to store user-defined passwords, keys, etc., the default Secret type;
• kubernetes.io/dockerconfigjson: used to store authentication information for private docker registry.

A Pod needs to reference a secret before it can use it. There are three ways for a Pod to use a secret:

• As a file mounted to a volume on one or more containers.
• As environment variables of the container.
• Used by kubelet when pulling images for Pods.

Application scenario: Credentials
https://kubernetes.io/docs/concepts/configuration/secret/

2. Create a secret instance

2.1 Use kubectl create secret command to create Secret

echo -n 'zhangsan' > username.txt
echo -n 'abc123' > password.txt

kubectl create secret generic mysecret --from-file=username.txt --from-file=password.txt

kubectl get secrets

#get或describe指令都不会展示secret的实际内容，这是出于对数据的保护的考虑
kubectl describe secret mysecret

2.2 Encode the content with base64 and create a secret

echo -n zhangsan | base64
emhhbmdzYW4=

echo -n abc123 | base64
YWJjMTIz

vim secret.yaml

apiVersion: v1
kind: Secret
metadata:
  name: mysecret1
type: Opaque
data:
  username: emhhbmdzYW4=
  password: YWJjMTIz

kubectl create -f secret.yaml 

kubectl get secrets

kubectl get secret mysecret1 -o yaml

apiVersion: v1
data:
  password: YWJjMTIz
  username: emhhbmdzYW4=
kind: Secret
metadata:
  creationTimestamp: "2023-03-02T07:15:01Z"
  managedFields:
  - apiVersion: v1
    fieldsType: FieldsV1
    fieldsV1:
      f:data:
        .: {}
        f:password: {}
        f:username: {}
      f:type: {}
    manager: kubectl-create
    operation: Update
    time: "2023-03-02T07:15:01Z"
  name: mysecret1
  namespace: default
  resourceVersion: "50956"
  uid: e611fddd-7ca1-4e75-8d3d-99478ab58a83
type: Opaque

3. How to use

3.1 Mount Secret to Volume and mount it to a directory of Pod in the form of Volume

vim secret-test.yaml

apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
  - name: nginx
    image: nginx
    volumeMounts:
    - name: secrets
      mountPath: "/etc/secrets"
      readOnly: true
  volumes:
  - name: secrets
    secret:
      secretName: mysecret

kubectl create -f secret-test.yaml

kubectl get pods

kubectl exec -it seret-test bash

3.2 Export secret to environment variables

vim secret-test1.yaml

apiVersion: v1
kind: Pod
metadata:
  name: mypod1
spec:
  containers:
  - name: nginx
    image: nginx
    env:
      - name: TEST_USER
        valueFrom:
          secretKeyRef:
            name: mysecret1
            key: username
      - name: TEST_PASSWORD
        valueFrom:
          secretKeyRef:
            name: mysecret1
            key: password

kubectl apply -f secret-test1.yaml 

kubectl get pods

kubectl exec -it mypod bash

2. ConfigMap

与Secret类似，区别在于ConfigMap保存的是不需要加密配置的信息。
ConfigMap 功能在 Kubernetes1.2 版本中引入，许多应用程序会从配置文件、命令行参数或环境变量中读取配置信息。ConfigMap API 给我们提供了向容器中注入配置信息的机制，ConfigMap 可以被用来保存单个属性，也可以用来保存整个配置文件或者JSON二进制大对象。
应用场景：应用配置

1、创建 ConfigMap

mkdir /opt/configmap/
 
vim /opt/configmap/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
 
vim /opt/configmap/ui.properties
color.good=purple
color.bad=yellow
allow.textmode=true
how.nice.to.look=fairlyNice

ls /opt/configmap/
game.properties
ui.properties

kubectl create configmap game-config --from-file=/opt/configmap/
#--from-file 指定在目录下的所有文件都会被用在 ConfigMap 里面创建一个键值对，键的名字就是文件名，值就是文件的内容

kubectl get cm

kubectl get cm game-config -o yaml

apiVersion: v1
data:
  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

kind: ConfigMap
metadata:
  creationTimestamp: "2023-03-02T10:31:37Z"
  managedFields:
  - apiVersion: v1
    fieldsType: FieldsV1
    fieldsV1:
      f:data:
        .: {}
        f:game.properties: {}
        f:ui.properties: {}
    manager: kubectl-create
    operation: Update
    time: "2023-03-02T10:31:37Z"
  name: game-config
  namespace: default
  resourceVersion: "65700"
  uid: 33ac77c9-8f0f-4d5e-a14d-763ac6e2be04

1.1 使用文件创建

只要指定为一个文件就可以从单个文件中创建 ConfigMap
--from-file 这个参数可以使用多次，即可以使用两次分别指定上个实例中的那两个配置文件，效果就跟指定整个目录是一样的

kubectl create configmap game-config-2 --from-file=/opt/configmap/game.properties --from-file=/opt/configmap/ui.properties

kubectl get configmaps game-config-2 -o yaml

kubectl describe cm game-config-2

1.2 使用字面值创建 

使用文字值创建，利用 --from-literal 参数传递配置信息，该参数可以使用多次，格式如下

kubectl create configmap special-config --from-literal=special.how=very --from-literal=special.type=good

kubectl get configmaps special-config -o yaml

apiVersion: v1
data:
  special.how: very    #key-value结构
  special.type: good
kind: ConfigMap
metadata:
  creationTimestamp: "2023-03-02T10:41:48Z"
  managedFields:
  - apiVersion: v1
    fieldsType: FieldsV1
    fieldsV1:
      f:data:
        .: {}
        f:special.how: {}
        f:special.type: {}
    manager: kubectl-create
    operation: Update
    time: "2023-03-02T10:41:48Z"
  name: special-config
  namespace: default
  resourceVersion: "66554"
  uid: 56e431fa-4833-458b-9a35-ab19f7dd3f77

kubectl delete cm --all

kubectl delete pod --all

2、Pod 中使用 ConfigMap

2.1 使用 ConfigMap 来替代环境变量

vim env.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: special-config
  namespace: default
data:
  special.how: very
  special.type: good
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: env-config
  namespace: default
data:
  log_level: INFO

kubectl create -f env.yaml 

kubectl get cm

Pod的创建

vim test-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: test-pod
spec:
  containers:
  - name: busybox
    image: busybox:1.28.4
    command: [ "/bin/sh", "-c", "env" ]
    env:
      - name: SPECIAL_HOW_KEY
        valueFrom:
          configMapKeyRef:
            name: special-config
            key: special.how
      - name: SPECIAL_TYPE_KEY
        valueFrom:
          configMapKeyRef:
            name: special-config
            key: special.type
    envFrom:
      - configMapRef:
          name: env-config
  restartPolicy: Never


kubectl create -f test-pod.yaml

kubectl get pods

kubectl logs pod-test

KUBERNETES_PORT=tcp://10.96.0.1:443
KUBERNETES_SERVICE_PORT=443
HOSTNAME=test-pod
SHLVL=1
SPECIAL_HOW_KEY=very   #赋值变量 SPECIAL_HOW_KEY 的值为 special-config 的
NGINX_PORT_80_TCP=tcp://10.105.252.176:80
SPECIAL_TYPE_KEY=good   #赋值变量 SPECIAL_TYPE_KEY 的值为 special-config 的
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
NGINX_SERVICE_HOST=10.105.252.176
KUBERNETES_PORT_443_TCP_PORT=443
KUBERNETES_PORT_443_TCP_PROTO=tcp
NGINX_PORT=tcp://10.105.252.176:80
NGINX_SERVICE_PORT=80
log_level=INFO     #引入 env-config 的变量 log_level: INFO
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
KUBERNETES_SERVICE_HOST=10.96.0.1
PWD=/
NGINX_PORT_80_TCP_ADDR=10.105.252.176
NGINX_PORT_80_TCP_PORT=80
NGINX_PORT_80_TCP_PROTO=tcp

2.2 用 ConfigMap 设置命令行参数

vim test-pod2.yaml
apiVersion: v1
kind: Pod
metadata:
  name: test-pod2
spec:
  containers:
  - name: busybox
    image: busybox:1.28.4
    command: 
	- /bin/sh
	- -c
	- echo "$(SPECIAL_HOW_KEY) $(SPECIAL_TYPE_KEY)"
    env:
      - name: SPECIAL_HOW_KEY
        valueFrom:
          configMapKeyRef:
            name: special-config
            key: special.how
      - name: SPECIAL_TYPE_KEY
        valueFrom:
          configMapKeyRef:
            name: special-config
            key: special.type
    envFrom:
      - configMapRef:
          name: env-config
  restartPolicy: Never


kubectl create -f test-pod2.yaml

kubectl get pods

kubectl logs test-pod2

2.3 通过数据卷插件使用ConfigMap 

在数据卷里面使用 ConfigMap，就是将文件填入数据卷，在这个文件中，键就是文件名，键值就是文件内容

vim test-pod3.yaml

apiVersion: v1
kind: Pod
metadata:
  name: test-pod3
spec:
  containers:
  - name: busybox
    image: busybox:1.28.4
    command: [ "/bin/sh", "-c", "sleep 36000" ]
    volumeMounts:
    - name: config-volume
      mountPath: /etc/config
  volumes:
    - name: config-volume
      configMap:
        name: special-config
  restartPolicy: Never


kubectl create -f test-pod3.yaml 

kubectl get pods

kubectl exec -it test-pod3 sh
 # cd /etc/config/
 # ls
special.how   special.type
 # vi special.how 
 # vi special.type

3、ConfigMap 的热更新 

vim test-pod4.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: log-config
  namespace: default
data:
  log_level: INFO
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: my-nginx
spec:
  replicas: 1
  template:
    metadata:
      labels:
        run: my-nginx
    spec:
      containers:
      - name: my-nginx
        image: nginx
        ports:
        - containerPort: 80
        volumeMounts:
        - name: config-volume
          mountPath: /etc/config
      volumes:
        - name: config-volume
          configMap:
            name: log-config

kubectl apply -f test-pod4.yaml

kubectl get pods 
NAME                        READY   STATUS    RESTARTS   AGE
my-nginx-76b6489f44-6dwxh   1/1     Running   0          46s

kubectl exec -it my-nginx-76b6489f44-6dwxh -- cat /etc/config/log_level
INFO

kubectl edit configmap log-config
apiVersion: v1
data:
  log_level: DEBUG		#INFO 修改成 DEBUG
kind: ConfigMap
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","data":{"log_level":"DEBUG"},"kind":"ConfigMap","metadata":{"annotations":{},"name":"log-config","namespace":"default"}}			#INFO 修改成 DEBUG
  creationTimestamp: 2021-05-25T07:59:18Z
  name: log-config
  namespace: default
  resourceVersion: "93616"
  selfLink: /api/v1/namespaces/default/configmaps/log-config
  uid: 1b8115de-bd2f-11eb-acba-000c29d88bba
  
#等大概10秒左右，使用该 ConfigMap 挂载的 Volume 中的数据同步更新 
kubectl exec -it my-nginx-76b6489f44-6dwxh -- cat /etc/config/log_level
DEBUG

#ConfigMap 更新后滚动更新 Pod
更新 ConfigMap 目前并不会触发相关 Pod 的滚动更新，可以通过在 .spec.template.metadata.annotations 中添加 version/config ，每次通过修改 version/config 来触发滚动更新

kubectl patch deployment my-nginx --patch '{"spec": {"template": {"metadata": {"annotations": {"version/config": "20210525" }}}}}'

kubectl get pods 
NAME                        READY   STATUS              RESTARTS   AGE
my-nginx-665dd4dc8c-j4k9t   0/1     ContainerCreating   0          4s
my-nginx-76b6489f44-6dwxh   0/1     Terminating         0          10m

kubectl get pods 
NAME                        READY   STATUS    RESTARTS   AGE
my-nginx-665dd4dc8c-j4k9t   1/1     Running   0          74s

PS：更新 ConfigMap 后：

• 使用该 ConfigMap 挂载的 Env 不会同步更新。
• 使用该 ConfigMap 挂载的 Volume 中的数据需要一段时间(实测大概10秒)才能同步更新。