coredns添加静态DNS的方法
思路：将node节点上/etc/hosts文件挂载到coredns容器中，通过修改coredns的configMap配置文件，使其能够读取到/etc/hosts文件中的内容
步骤1：修改coredns的configMap
执行命令：kubectl -n kube-system edit configmap coredns
在'health'这一行下添加如下内容：
hosts /etc/add_hosts {
fallthrough
}
完整的内容如下：
# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: v1
data:
Corefile: |
.:53 {
errors
log stdout
health
hosts /etc/add_hosts {
fallthrough
}
kubernetes cluster.local 10.96.0.0/12 {
pods insecure
}
prometheus
proxy . /etc/resolv.conf
cache 30
}
kind: ConfigMap
metadata:
creationTimestamp: 2019-03-25T11:17:14Z
name: coredns
namespace: kube-system
resourceVersion: "2714953"
selfLink: /api/v1/namespaces/kube-system/configmaps/coredns
uid: 8ad75e15-4eef-11e9-bd35-384c4fcc700e
步骤2：修改coredns的deployment
挂载node节点的/etc/hosts目录，执行命令：kubectl -n kube-system edit deployment coredns
在'volumeMounts:'这一行下增加如下内容：
- mountPath: /etc/add_hosts
name: add-hosts
在'volumes:'这一行下增加如下内容：
- hostPath:
path: /etc/hosts
type: ""
name: add-hosts
完整内容如下：
# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
annotations:
deployment.kubernetes.io/revision: "2"
creationTimestamp: 2019-03-25T11:17:14Z
generation: 4
labels:
k8s-app: kube-dns
name: coredns
namespace: kube-system
resourceVersion: "2716032"
selfLink: /apis/extensions/v1beta1/namespaces/kube-system/deployments/coredns
uid: 8aedd1f5-4eef-11e9-bd35-384c4fcc700e
spec:
progressDeadlineSeconds: 600
replicas: 1
revisionHistoryLimit: 10
selector:
matchLabels:
k8s-app: kube-dns
strategy:
rollingUpdate:
maxSurge: 25%
maxUnavailable: 25%
type: RollingUpdate
template:
metadata:
creationTimestamp: null
labels:
k8s-app: kube-dns
spec:
containers:
- args:
- -conf
- /etc/coredns/Corefile
image: coredns/coredns:1.0.0
imagePullPolicy: IfNotPresent
livenessProbe:
failureThreshold: 5
httpGet:
path: /health
port: 8080
scheme: HTTP
initialDelaySeconds: 60
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 5
name: coredns
ports:
- containerPort: 53
name: dns
protocol: UDP
- containerPort: 53
name: dns-tcp
protocol: TCP
- containerPort: 9153
name: metrics
protocol: TCP
resources:
limits:
memory: 170Mi
requests:
cpu: 100m
memory: 70Mi
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /etc/add_hosts
name: add-hosts
- mountPath: /etc/coredns
name: config-volume
dnsPolicy: Default
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
serviceAccount: coredns
serviceAccountName: coredns
terminationGracePeriodSeconds: 30
tolerations:
- key: CriticalAddonsOnly
operator: Exists
- effect: NoSchedule
key: node-role.kubernetes.io/master
volumes:
- hostPath:
path: /etc/hosts
type: ""
name: add-hosts
- configMap:
defaultMode: 420
items:
- key: Corefile
path: Corefile
name: coredns
name: config-volume
status:
availableReplicas: 1
conditions:
- lastTransitionTime: 2019-03-25T11:18:49Z
lastUpdateTime: 2019-03-25T11:18:49Z
message: Deployment has minimum availability.
reason: MinimumReplicasAvailable
status: "True"
type: Available
- lastTransitionTime: 2019-03-25T11:17:29Z
lastUpdateTime: 2019-03-28T06:45:14Z
message: ReplicaSet "coredns-c89d9c56b" has successfully progressed.
reason: NewReplicaSetAvailable
status: "True"
type: Progressing
observedGeneration: 4
readyReplicas: 1
replicas: 1
updatedReplicas: 1