biglittleant

不被嘲笑的梦想,是不值得去实现的

0%

coredns服务搭建

下载和配置 coredns

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cd /data/apps/k8s/work/
git clone https://github.com/coredns/deployment.git
mv deployment coredns-deployment

创建 coredns

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cd /data/apps/k8s/work/coredns-deployment/kubernetes
export CLUSTER_DNS_SVC_IP="10.254.0.2"
export CLUSTER_DNS_DOMAIN="cluster.local"
./deploy.sh -i ${CLUSTER_DNS_SVC_IP} -d ${CLUSTER_DNS_DOMAIN} > coredns.yaml
kubectl apply -f coredns.yaml

Sep 27 15:35:22 node1 kube-scheduler[8420]: I0927 15:35:22.343021 8420 scheduler.go:667] pod kube-system/coredns-759df9d7b-td7rr is bound successfully on node “node7”, 2 nodes evaluated, 2 nodes were found feasible. Bound node resource: “Capacity: CPU<2>|Memory<4046008Ki>|Pods<220>|StorageEphemeral<41921540Ki>; Allocatable: CPU<2>|Memory<3943608Ki>|Pods<220>|StorageEphemeral<38634891201>.”.

检查 coredns 功能

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$ kubectl get all -n kube-system -l k8s-app=kube-dns
NAME READY STATUS RESTARTS AGE
pod/coredns-759df9d7b-td7rr 1/1 Running 0 2m7s

NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kube-dns ClusterIP 10.254.0.2 <none> 53/UDP,53/TCP,9153/TCP 2m7s

NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/coredns 1/1 1 1 2m7s

NAME DESIRED CURRENT READY AGE
replicaset.apps/coredns-759df9d7b 1 1 1 2m7s

新建一个 Deployment:

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cd /data/apps/k8s/work/
cat > my-nginx.yaml <<EOF
apiVersion: apps/v1
kind: Deployment
metadata:
name: my-nginx
spec:
replicas: 2
selector:
matchLabels:
run: my-nginx
template:
metadata:
labels:
run: my-nginx
spec:
containers:
- name: my-nginx
image: nginx:1.7.9
ports:
- containerPort: 80
EOF
kubectl create -f my-nginx.yaml

export 该 Deployment, 生成 my-nginx 服务:

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$ kubectl expose deploy my-nginx
service "my-nginx" exposed

$ kubectl get services my-nginx -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
my-nginx ClusterIP 10.254.67.218 <none> 80/TCP 5s run=my-nginx

创建另一个 Pod,查看 /etc/resolv.conf 是否包含 kubelet 配置的 --cluster-dns--cluster-domain,是否能够将服务 my-nginx 解析到上面显示的 Cluster IP 10.254.67.218

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cd /data/apps/k8s/work/
cat > dnsutils-ds.yml <<EOF
apiVersion: v1
kind: Service
metadata:
name: dnsutils-ds
labels:
app: dnsutils-ds
spec:
type: NodePort
selector:
app: dnsutils-ds
ports:
- name: http
port: 80
targetPort: 80
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: dnsutils-ds
labels:
addonmanager.kubernetes.io/mode: Reconcile
spec:
selector:
matchLabels:
app: dnsutils-ds
template:
metadata:
labels:
app: dnsutils-ds
spec:
containers:
- name: my-dnsutils
image: tutum/dnsutils:latest
command:
- sleep
- "3600"
ports:
- containerPort: 80
EOF
kubectl create -f dnsutils-ds.yml
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$ kubectl get pods -l app=dnsutils-ds -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
dnsutils-ds-t5hqb 1/1 Running 0 4m25s 172.30.139.3 node6 <none> <none>
dnsutils-ds-zxzhf 1/1 Running 0 4m25s 172.30.199.195 node7 <none> <none>
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$ kubectl -it exec dnsutils-ds-t5hqb  cat /etc/resolv.conf
search default.svc.cluster.local svc.cluster.local cluster.local
nameserver 10.254.0.2
options ndots:5

查看一下现有的server

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$ kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
dnsutils-ds NodePort 10.254.242.169 <none> 80:31128/TCP 6m36s
kubernetes ClusterIP 10.254.0.1 <none> 443/TCP 146m
my-nginx ClusterIP 10.254.2.160 <none> 80/TCP 8m27s

nslookup 验证一下解析信息

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$ kubectl -it exec dnsutils-ds-t5hqb nslookup kubernetes
Server: 10.254.0.2
Address: 10.254.0.2#53

Name: kubernetes.default.svc.cluster.local
Address: 10.254.0.1
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$ kubectl -it exec dnsutils-ds-t5hqb nslookup my-nginx
Server: 10.254.0.2
Address: 10.254.0.2#53

Name: my-nginx.default.svc.cluster.local
Address: 10.254.2.160

nslookup 验证一下外网域名

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$ kubectl -it exec dnsutils-ds-t5hqb  nslookup www.baidu.com
Server: 10.254.0.2
Address: 10.254.0.2#53

Non-authoritative answer:
www.baidu.com canonical name = www.a.shifen.com.
Name: www.a.shifen.com
Address: 39.156.66.18
Name: www.a.shifen.com
Address: 39.156.66.14

参考

  1. https://community.infoblox.com/t5/Community-Blog/CoreDNS-for-Kubernetes-Service-Discovery/ba-p/8187
  2. https://coredns.io/2017/03/01/coredns-for-kubernetes-service-discovery-take-2/
  3. https://www.cnblogs.com/boshen-hzb/p/7511432.html
  4. https://github.com/kubernetes/kubernetes/tree/master/cluster/addons/dns