CentOS 7簇

Question

我一直在努力让DNS插件在CentOS 7.2集群上工作。我使用以下说明安装了集群：http://severalnines.com/blog/installing-kubernetes-cluster-minions-centos7-manage-pods-services

在此配置中，主机正在运行: etcd、kube-调度器、kube-apiserver和kube-控制器-管理器.节点正在运行: docker、kubelet和kubelet和flanneld。在此配置中，集群运行良好。豆荚，仆人都在工作。下一步是尝试启用DNS。

注：此群集不使用证书进行身份验证。

关于如何做到这一点，有几个“指南”，但似乎没有一个在这种类型的集群上工作。

首先，你能帮我澄清一些困惑吗？dns附件容器在哪里运行？

• 他们一定要在大师身上跑吗？
• 它们能像集群上的任何其他吊舱一样部署吗？

以下是我到目前为止尝试过的：

库伯奈特斯版本:香草安装从百胜。

# kubectl version
Client Version: version.Info{Major:"1", Minor:"2", GitVersion:"v1.2.0"  GitCommit:"a4463d9a1accc9c61ae90ce5d314e248f16b9f05", GitTreeState:"clean"}    
Server Version: version.Info{Major:"1", Minor:"2", GitVersion:"v1.2.0", GitCommit:"a4463d9a1accc9c61ae90ce5d314e248f16b9f05", GitTreeState:"clean"}

在下面的sky-dns.yaml文件中，我用一个复制集替换了模板变量，将DNS_DOMAIN设置为"cluster.local“。我在http://10.2.1.245:8080上的一些建议中增加了一个命令行到“/kube”容器--kube url= StackOverflow“。

SkyDNS-rc.yaml (指向kube的v18 )

apiVersion: v1
kind: ReplicationController
metadata:
  name: kube-dns-v18
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    version: v18
    kubernetes.io/cluster-service: "true"
spec:
  replicas: 1
  selector:
    k8s-app: kube-dns
    version: v18
  template:
    metadata:
      labels:
        k8s-app: kube-dns
        version: v18
        kubernetes.io/cluster-service: "true"
    spec:
      containers:
      - name: kubedns
        image: gcr.io/google_containers/kubedns-amd64:1.6
        resources:
          # TODO: Set memory limits when we've profiled the container for large
          # clusters, then set request = limit to keep this container in
          # guaranteed class. Currently, this container falls into the
          # "burstable" category so the kubelet doesn't backoff from restarting it.
          limits:
            cpu: 100m
            memory: 200Mi
          requests:
            cpu: 100m
            memory: 100Mi
        livenessProbe:
          httpGet:
            path: /healthz
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        readinessProbe:
          httpGet:
            path: /readiness
            port: 8081
            scheme: HTTP
          # we poll on pod startup for the Kubernetes master service and
          # only setup the /readiness HTTP server once that's available.
          initialDelaySeconds: 30
          timeoutSeconds: 5
        args:
        # command = "/kube-dns"
        - --domain=cluster.local
        - --dns-port=10053
        - --kube-master-url=http://10.2.1.245:8080
        ports:
        - containerPort: 10053
          name: dns-local
          protocol: UDP
        - containerPort: 10053
          name: dns-tcp-local
          protocol: TCP
      - name: dnsmasq
        image: gcr.io/google_containers/kube-dnsmasq-amd64:1.3
        args:
        - --cache-size=1000
        - --no-resolv
        - --server=127.0.0.1#10053
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
      - name: healthz
        image: gcr.io/google_containers/exechealthz-amd64:1.0
        resources:
          # keep request = limit to keep this container in guaranteed class
          limits:
            cpu: 10m
            memory: 20Mi
          requests:
            cpu: 10m
            memory: 20Mi
        args:
        - -cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1 >/dev/null && nslookup kubernetes.default.svc.cluster.local 127.0.0.1:10053 >/dev/null
        - -port=8080
        - -quiet
        ports:
        - containerPort: 8080
          protocol: TCP
      dnsPolicy: Default  # Don't use cluster DNS.

在每个节点(主节点和3个分支)上，我更新了/etc/kubernetes/conf文件，在末尾添加了DSN部分(完整地发布了完整的文件)。

如果我使用上面的复制控制器，是否需要添加这些？

/etc/kubernetes/conf

# logging to stderr means we get it in the systemd journal
KUBE_LOGTOSTDERR="--logtostderr=true"

# journal message level, 0 is debug
KUBE_LOG_LEVEL="--v=0"

# Should this cluster be allowed to run privileged docker containers
KUBE_ALLOW_PRIV="--allow-privileged=false"

# How the controller-manager, scheduler, and proxy find the apiserver
KUBE_MASTER="--master=http://127.0.0.1:8080"

# DNS Add-on
ENABLE_CLUSTER_DNS="${KUBE_ENABLE_CLUSTER_DNS:-true}"
DNS_SERVER_IP="10.254.100.1"
DNS_DOMAIN="cluster.local"
DNS_REPLICAS=1

下面是我在部署KubeDNS时看到的情况。

[root@dcook-kube-c1 dcook]# kubectl create -f kube-fun/skydns-rc.yaml
replicationcontroller "kube-dns-v18" created

[root@dcook-kube-c1 dcook]# kubectl get rc kube-dns-v18 --namespace kube-system
NAME           DESIRED   CURRENT   AGE
kube-dns-v18   1         1         34s

[root@dcook-kube-c1 dcook]# kubectl get pods --namespace kube-system
NAME                 READY     STATUS             RESTARTS   AGE
kube-dns-v18-cx4ir   3/3       Running            0          46s

日志：

[root@dcook-kube-c1 dcook]# kubectl logs --namespace="kube-system" kube-dns-v18-cx4ir kubedns
I0726 20:17:52.675064       1 server.go:91] Using http://10.2.1.245:8080 for kubernetes master
I0726 20:17:52.676138       1 server.go:92] Using kubernetes API v1
I0726 20:17:52.676498       1 server.go:132] Starting SkyDNS server. Listening on port:10053
I0726 20:17:52.676815       1 server.go:139] skydns: metrics enabled on :/metrics
I0726 20:17:52.676836       1 dns.go:166] Waiting for service: default/kubernetes
I0726 20:17:52.677584       1 logs.go:41] skydns: ready for queries on cluster.local. for tcp://0.0.0.0:10053 [rcache 0]
I0726 20:17:52.677604       1 logs.go:41] skydns: ready for queries on cluster.local. for udp://0.0.0.0:10053 [rcache 0]
I0726 20:17:52.867455       1 server.go:101] Setting up Healthz Handler(/readiness, /cache) on port :8081
I0726 20:17:52.867843       1 dns.go:660] DNS Record:&{10.254.0.1 0 10 10  false 30 0  }, hash:63b49cf0
I0726 20:17:52.867898       1 dns.go:660] DNS Record:&{kubernetes.default.svc.cluster.local. 443 10 10  false 30 0  }, hash:c3f6ae26
I0726 20:17:52.868048       1 dns.go:660] DNS Record:&{kubernetes.default.svc.cluster.local. 0 10 10  false 30 0  }, hash:b9b7d845
I0726 20:17:52.868103       1 dns.go:660] DNS Record:&{10.254.91.7 0 10 10  false 30 0  }, hash:9b59fd9c
I0726 20:17:52.868137       1 dns.go:660] DNS Record:&{my-nginx.default.svc.cluster.local. 0 10 10  false 30 0  }, hash:b0f41a92

[root@dcook-kube-c1 dcook]# kubectl logs --namespace="kube-system" kube-dns-v18-cx4ir healthz
2016/07/26 20:17:11 Healthz probe error: Result of last exec: nslookup: can't resolve 'kubernetes.default.svc.cluster.local'
, at 2016-07-26 20:17:10.667247682 +0000 UTC, error exit status 1
2016/07/26 20:17:21 Healthz probe error: Result of last exec: nslookup: can't resolve 'kubernetes.default.svc.cluster.local'
, at 2016-07-26 20:17:20.667213321 +0000 UTC, error exit status 1
2016/07/26 20:17:31 Healthz probe error: Result of last exec: nslookup: can't resolve 'kubernetes.default.svc.cluster.local'
, at 2016-07-26 20:17:30.667225804 +0000 UTC, error exit status 1
2016/07/26 20:17:41 Healthz probe error: Result of last exec: nslookup: can't resolve 'kubernetes.default.svc.cluster.local'
, at 2016-07-26 20:17:40.667218056 +0000 UTC, error exit status 1
2016/07/26 20:17:51 Healthz probe error: Result of last exec: nslookup: can't resolve 'kubernetes.default.svc.cluster.local'
, at 2016-07-26 20:17:50.667724036 +0000 UTC, error exit status 1

Answer 1

您缺少了一个暴露您的吊舱的服务：https://github.com/kubernetes/kubernetes/blob/master/cluster/addons/dns/skydns-svc.yaml.in

在这里您设置了ClusterIP，然后在启动kubelet时需要使用它。

您需要使用--cluster_dns=<the IP you used in the service> --cluster_domain=cluster.local启动kubelets

另外，我会将您的rc更新为最新版本(v19)，类似于您在这里看到的内容：https://github.com/kubernetes/kubernetes/blob/master/cluster/addons/dns/skydns-rc.yaml.in。