19-k8s的附加组件-coreDNS组件

一、概念

coreDNS组件：就是将svc资源的名称解析成ClusterIP；

kubeadm部署的k8s集群自带coreDNS组件，二进制部署需要自己手动部署；

[root@k8s231 ~]# kubectl get pods -o wide -A

k8s系统中安装了coreDNS组件后，会有一个coreDNS开头的pod资源；

二、查看k8s集群的coreDNS的IP地址

查看kubelet的配置文件中，可以看到集群dns的地址；

[root@k8s231 ~]# vim /var/lib/kubelet/config.yaml

............
clusterDNS:
- 10.200.0.10
clusterDomain: xinjizhiwa.com

...............

[root@k8s231 ~]# kubectl get svc -A

查看k8s集群中DNS的svc的详细信息，可以看到，里面解析了coreDNS的地址在endpoint列表中；

[root@k8s231 ~]# kubectl describe -n kube-system svc kube-dns

三、测试coreDNS组件是否正常

1，第一种方式验证

· 准备wordpress的案例的资源文件

[root@k8s231 dns]# ll
total 12
-rw-r--r-- 1 root root 574 Feb 17 22:47 db.yaml
-rw-r--r-- 1 root root 599 Feb 17 22:51 deploy.yaml
-rw-r--r-- 1 root root 411 Feb 17 22:50 svc.yaml

[root@k8s231 dns]# cat deploy.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: dm-wordpress
spec:
replicas: 1
selector:
matchLabels:
k8s: k8s
template:
metadata:
labels:
k8s: k8s
spec:
containers:
- name: wp-c
image: wordpress:latest
ports:
- name: wp-port
containerPort: 80
env:
- name: WORDPRESS_DB_HOST
value: 10.200.22.22:3306
- name: WORDPRESS_DB_USER
value: wordpress
- name: WORDPRESS_DB_PASSWORD
value: wordpress
- name: WORDPRESS_DB_NAME
value: wordpress

[root@k8s231 dns]# cat db.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: wordpress-db
spec:
replicas: 1
selector:
matchLabels:
k8s: db
template:
metadata:
labels:
k8s: db
spec:
containers:
- name: db-c
image: mysql:8.0
ports:
- name: db-port
containerPort: 3306
env:
- name: MYSQL_DATABASE
value: wordpress
- name: MYSQL_USER
value: wordpress
- name: MYSQL_PASSWORD
value: wordpress
- name: MYSQL_ROOT_PASSWORD
value: wordpress

[root@k8s231 dns]# cat svc.yaml
apiVersion: v1
kind: Service
metadata:
name: svc-db
spec:
type: NodePort
clusterIP: 10.200.22.22
selector:
k8s: db
ports:
- protocol: TCP
port: 3306
targetPort: 3306
nodePort: 30001
---
apiVersion: v1
kind: Service
metadata:
name: svc-wp
spec:
type: NodePort
selector:
k8s: k8s
ports:
- protocol: TCP
port: 80
targetPort: 80
nodePort: 30000