kubernetes实践之六十四：CoreDNS

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1. $ ./deploy.sh | kubectl apply -f -
   
2. $ kubectl delete --namespace=kube-system deployment kube-dns

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1. #!/bin/bash
   
2. 
   
3. # Deploys CoreDNS to a cluster currently running Kube-DNS.
   
4. 
   
5. show_help () {
   
6. cat << USAGE
   
7. usage: $0 [ -r REVERSE-CIDR ] [ -i DNS-IP ] [ -d CLUSTER-DOMAIN ] [ -t YAML-TEMPLATE ]
   
8. -r : Define a reverse zone for the given CIDR. You may specifcy this option more
   
9. than once to add multiple reverse zones. If no reverse CIDRs are defined,
   
10. then the default is to handle all reverse zones (i.e. in-addr.arpa and ip6.arpa)
    
11. -i : Specify the cluster DNS IP address. If not specificed, the IP address of
    
12. the existing "kube-dns" service is used, if present.
    
13. USAGE
    
14. exit 0
    
15. }
    
16. 
    
17. # Simple Defaults
    
18. CLUSTER_DOMAIN=cluster.local
    
19. YAML_TEMPLATE=`pwd`/coredns.yaml.sed
    
20. 
    
21. 
    
22. # Get Opts
    
23. while getopts "hr:i:d:t:" opt; do
    
24. case "$opt" in
    
25. h) show_help
    
26. ;;
    
27. r) REVERSE_CIDRS="$REVERSE_CIDRS $OPTARG"
    
28. ;;
    
29. i) CLUSTER_DNS_IP=$OPTARG
    
30. ;;
    
31. d) CLUSTER_DOMAIN=$OPTARG
    
32. ;;
    
33. t) YAML_TEMPLATE=$OPTARG
    
34. ;;
    
35. esac
    
36. done
    
37. 
    
38. # Conditional Defaults
    
39. if [[ -z $REVERSE_CIDRS ]]; then
    
40. REVERSE_CIDRS="in-addr.arpa ip6.arpa"
    
41. fi
    
42. if [[ -z $CLUSTER_DNS_IP ]]; then
    
43. # Default IP to kube-dns IP
    
44. CLUSTER_DNS_IP=$(kubectl get service --namespace kube-system kube-dns -o jsonpath="{.spec.clusterIP}")
    
45. if [ $? -ne 0 ]; then
    
46. >&2 echo "Error! The IP address for DNS service couldn't be determined automatically. Please specify the DNS-IP with the '-i' option."
    
47. exit 2
    
48. fi
    
49. fi
    
50. 
    
51. sed -e s/CLUSTER_DNS_IP/$CLUSTER_DNS_IP/g -e s/CLUSTER_DOMAIN/$CLUSTER_DOMAIN/g -e "s?REVERSE_CIDRS?$REVERSE_CIDRS?g" $YAML_TEMPLATE

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1. apiVersion: v1
   
2. kind: ServiceAccount
   
3. metadata:
   
4. name: coredns
   
5. namespace: kube-system
   
6. ---
   
7. apiVersion: rbac.authorization.k8s.io/v1beta1
   
8. kind: ClusterRole
   
9. metadata:
   
10. labels:
    
11. kubernetes.io/bootstrapping: rbac-defaults
    
12. name: system:coredns
    
13. rules:
    
14. - apiGroups:
    
15. - ""
    
16. resources:
    
17. - endpoints
    
18. - services
    
19. - pods
    
20. - namespaces
    
21. verbs:
    
22. - list
    
23. - watch
    
24. ---
    
25. apiVersion: rbac.authorization.k8s.io/v1beta1
    
26. kind: ClusterRoleBinding
    
27. metadata:
    
28. annotations:
    
29. rbac.authorization.kubernetes.io/autoupdate: "true"
    
30. labels:
    
31. kubernetes.io/bootstrapping: rbac-defaults
    
32. name: system:coredns
    
33. roleRef:
    
34. apiGroup: rbac.authorization.k8s.io
    
35. kind: ClusterRole
    
36. name: system:coredns
    
37. subjects:
    
38. - kind: ServiceAccount
    
39. name: coredns
    
40. namespace: kube-system
    
41. ---
    
42. apiVersion: v1
    
43. kind: ConfigMap
    
44. metadata:
    
45. name: coredns
    
46. namespace: kube-system
    
47. data:
    
48. Corefile: |
    
49. .:53 {
    
50. errors
    
51. health
    
52. kubernetes CLUSTER_DOMAIN REVERSE_CIDRS {
    
53. pods insecure
    
54. upstream
    
55. fallthrough in-addr.arpa ip6.arpa
    
56. }
    
57. prometheus :9153
    
58. proxy . /etc/resolv.conf
    
59. cache 30
    
60. reload
    
61. }
    
62. ---
    
63. apiVersion: extensions/v1beta1
    
64. kind: Deployment
    
65. metadata:
    
66. name: coredns
    
67. namespace: kube-system
    
68. labels:
    
69. k8s-app: kube-dns
    
70. kubernetes.io/name: "CoreDNS"
    
71. spec:
    
72. replicas: 2
    
73. strategy:
    
74. type: RollingUpdate
    
75. rollingUpdate:
    
76. maxUnavailable: 1
    
77. selector:
    
78. matchLabels:
    
79. k8s-app: kube-dns
    
80. template:
    
81. metadata:
    
82. labels:
    
83. k8s-app: kube-dns
    
84. spec:
    
85. serviceAccountName: coredns
    
86. tolerations:
    
87. - key: "CriticalAddonsOnly"
    
88. operator: "Exists"
    
89. containers:
    
90. - name: coredns
    
91. image: coredns/coredns:1.1.3
    
92. imagePullPolicy: IfNotPresent
    
93. args: [ "-conf", "/etc/coredns/Corefile" ]
    
94. volumeMounts:
    
95. - name: config-volume
    
96. mountPath: /etc/coredns
    
97. readOnly: true
    
98. ports:
    
99. - containerPort: 53
    
100. name: dns
     
101. protocol: UDP
     
102. - containerPort: 53
     
103. name: dns-tcp
     
104. protocol: TCP
     
105. - containerPort: 9153
     
106. name: metrics
     
107. protocol: TCP
     
108. securityContext:
     
109. allowPrivilegeEscalation: false
     
110. capabilities:
     
111. add:
     
112. - NET_BIND_SERVICE
     
113. drop:
     
114. - all
     
115. readOnlyRootFilesystem: true
     
116. livenessProbe:
     
117. httpGet:
     
118. path: /health
     
119. port: 8080
     
120. scheme: HTTP
     
121. initialDelaySeconds: 60
     
122. timeoutSeconds: 5
     
123. successThreshold: 1
     
124. failureThreshold: 5
     
125. dnsPolicy: Default
     
126. volumes:
     
127. - name: config-volume
     
128. configMap:
     
129. name: coredns
     
130. items:
     
131. - key: Corefile
     
132. path: Corefile
     
133. ---
     
134. apiVersion: v1
     
135. kind: Service
     
136. metadata:
     
137. name: kube-dns
     
138. namespace: kube-system
     
139. annotations:
     
140. prometheus.io/scrape: "true"
     
141. labels:
     
142. k8s-app: kube-dns
     
143. kubernetes.io/cluster-service: "true"
     
144. kubernetes.io/name: "CoreDNS"
     
145. spec:
     
146. selector:
     
147. k8s-app: kube-dns
     
148. clusterIP: CLUSTER_DNS_IP
     
149. ports:
     
150. - name: dns
     
151. port: 53
     
152. protocol: UDP
     
153. - name: dns-tcp
     
154. port: 53
     
155. protocol: TCP