目录
- 叙述
- 安装
- 测试 一
- 测试 二 CoreDNS
叙述
截止到目前为止，整个集群的核心组件已经安装完成。
此时集群内部还需要 CoreDNS 组件的支持。
安装
CoreDNS 是以 Pod 的形式运行在 k8s 集群内部；
创建下面的 yaml 文件：
[root@node01 work]# cd /opt/k8s/work/
[root@node01 work]# cat coredns.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: coredns
namespace: kube-system
labels:
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: Reconcile
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
labels:
kubernetes.io/bootstrapping: rbac-defaults
addonmanager.kubernetes.io/mode: Reconcile
name: system:coredns
rules:
- apiGroups:
- ""
resources:
- endpoints
- services
- pods
- namespaces
verbs:
- list
- watch
- apiGroups:
- ""
resources:
- nodes
verbs:
- get
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
annotations:
rbac.authorization.kubernetes.io/autoupdate: "true"
labels:
kubernetes.io/bootstrapping: rbac-defaults
addonmanager.kubernetes.io/mode: EnsureExists
name: system:coredns
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:coredns
subjects:
- kind: ServiceAccount
name: coredns
namespace: kube-system
---
apiVersion: v1
kind: ConfigMap
metadata:
name: coredns
namespace: kube-system
labels:
addonmanager.kubernetes.io/mode: EnsureExists
data:
Corefile: |
.:53 {
errors
health
kubernetes cluster.local in-addr.arpa ip6.arpa {
pods insecure
upstream
fallthrough in-addr.arpa ip6.arpa
}
prometheus :9153
forward . /etc/resolv.conf
cache 30
loop
reload
loadbalance
}
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: coredns
namespace: kube-system
labels:
k8s-app: kube-dns
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: Reconcile
kubernetes.io/name: "CoreDNS"
spec:
replicas: 2
# replicas: not specified here:
# 1. In order to make Addon Manager do not reconcile this replicas parameter.
# 2. Default is 1.
# 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on.
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 1
selector:
matchLabels:
k8s-app: kube-dns
template:
metadata:
labels:
k8s-app: kube-dns
annotations:
seccomp.security.alpha.kubernetes.io/pod: 'docker/default'
spec:
priorityClassName: system-cluster-critical
serviceAccountName: coredns
tolerations:
- key: "CriticalAddonsOnly"
operator: "Exists"
nodeSelector:
beta.kubernetes.io/os: linux
containers:
- name: coredns
image: coredns/coredns:1.4.0
imagePullPolicy: IfNotPresent
resources:
limits:
memory: 170Mi
requests:
cpu: 100m
memory: 70Mi
args: [ "-conf", "/etc/coredns/Corefile" ]
volumeMounts:
- name: host-time
mountPath: /etc/localtime
readOnly: true
- name: config-volume
mountPath: /etc/coredns
readOnly: true
ports:
- containerPort: 53
name: dns
protocol: UDP
- containerPort: 53
name: dns-tcp
protocol: TCP
- containerPort: 9153
name: metrics
protocol: TCP
livenessProbe:
httpGet:
path: /health
port: 8080
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
readinessProbe:
httpGet:
path: /health
port: 8080
scheme: HTTP
securityContext:
allowPrivilegeEscalation: false
capabilities:
add:
- NET_BIND_SERVICE
drop:
- all
readOnlyRootFilesystem: true
dnsPolicy: Default
volumes:
- name: host-time
hostPath:
path: /etc/localtime
- name: config-volume
configMap:
name: coredns
items:
- key: Corefile
path: Corefile
---
apiVersion: v1
kind: Service
metadata:
name: kube-dns
namespace: kube-system
annotations:
prometheus.io/port: "9153"
prometheus.io/scrape: "true"
labels:
k8s-app: kube-dns
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: Reconcile
kubernetes.io/name: "CoreDNS"
spec:
selector:
k8s-app: kube-dns
clusterIP: 10.254.0.2
ports:
- name: dns
port: 53
protocol: UDP
- name: dns-tcp
port: 53
protocol: TCP
- name: metrics
port: 9153
protocol: TCP执行 coredns.yaml 文件：
[root@node01 work]# kubectl apply -f coredns.yaml
serviceaccount/coredns created
clusterrole.rbac.authorization.k8s.io/system:coredns created
clusterrolebinding.rbac.authorization.k8s.io/system:coredns created
configmap/coredns created
deployment.apps/coredns created
service/kube-dns created查看结果
[root@node01 work]# kubectl get pods -n kube-system -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
coredns-5c6c9cf6c8-gbhvd 1/1 Running 0 41s 172.30.160.2 node02
coredns-5c6c9cf6c8-rtrc5 1/1 Running 0 41s 172.30.48.2 node04 测试 一
创建测试yaml文件
cd /opt/k8s/work
cat > nginx-ds.yml <执行
[root@node01 work]# kubectl apply -f nginx-ds.yml
service/nginx-ds created
daemonset.extensions/nginx-ds created[root@node01 work]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-ds-4cdb6 1/1 Running 0 28s 172.30.160.3 node02
nginx-ds-4l8pv 1/1 Running 0 28s 172.30.80.2 node03
nginx-ds-jfz8l 1/1 Running 0 28s 172.30.48.3 node04
nginx-ds-pmhw7 1/1 Running 0 28s 172.30.224.2 node01
[root@node01 work]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.254.0.1 443/TCP 7h1m
nginx-ds NodePort 10.254.7.236 80:22415/TCP 33s 测试访问
[root@node01 work]# curl -I 10.0.20.11:22415
HTTP/1.1 200 OK
Server: nginx/1.13.0
Date: Thu, 05 Dec 2019 13:31:18 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Wed, 10 May 2017 21:50:27 GMT
Connection: keep-alive
ETag: "59138b23-264"
Accept-Ranges: bytes可以看到 NodePort 模式的 SVC 已经可以访问；
测试 二 CoreDNS
创建一个 busybox 的 pod，进入pod 解析
cat<[root@node01 work]# kubectl get pods
NAME READY STATUS RESTARTS AGE
busybox 1/1 Running 0 18s测试解析集群内部解析:
[root@node01 work]# kubectl exec -it busybox -- nslookup kubernetes
Server: 10.254.0.2
Address 1: 10.254.0.2 kube-dns.kube-system.svc.cluster.local
Name: kubernetes
Address 1: 10.254.0.1 kubernetes.default.svc.cluster.local测试解析刚刚创建的nginx 的SVC：
[root@node01 work]# kubectl exec -it busybox -- nslookup nginx-ds.default.svc.cluster.local.
Server: 10.254.0.2
Address 1: 10.254.0.2 kube-dns.kube-system.svc.cluster.local
Name: nginx-ds.default.svc.cluster.local.
Address 1: 10.254.7.236 nginx-ds.default.svc.cluster.local
[root@node01 work]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.254.0.1 443/TCP 7h5m
nginx-ds NodePort 10.254.7.236 80:22415/TCP 4m7s 至此集群安装结束；