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kubelet can not set cluster dns parameter using kube-dns

7/13/2018

I have a problem when I set kubelet parameter cluster-dns

My OS is CentOS Linux release 7.0.1406 (Core)
Kernel:Linux master 3.10.0-693.el7.x86_64 #1 SMP Tue Aug 22 21:09:27 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

kubelet config file:

KUBELET_HOSTNAME="--hostname-override=master"
#KUBELET_API_SERVER="--api-servers=http://master:8080
KUBECONFIG="--kubeconfig=/root/.kube/config-demo"
KUBELET_DNS="–-cluster-dns=10.254.0.10"
KUBELET_DOMAIN="--cluster-domain=cluster.local"
# Add your own!
KUBELET_ARGS="--cgroup-driver=systemd --fail-swap-on=false --pod_infra_container_image=177.1.1.35/library/pause:latest"

config file:

KUBE_LOGTOSTDERR="--logtostderr=true"  
KUBE_LOG_LEVEL="--v=4"
KUBE_ALLOW_PRIV="--allow-privileged=false"
KUBE_MASTER="--master=http://master:8080"

kubelet.service file:

[Unit]
Description=Kubernetes Kubelet Server
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
After=docker.service
Requires=docker.service

[Service]
WorkingDirectory=/var/lib/kubelet
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/kubelet
ExecStart=/usr/bin/kubelet \
            $KUBE_LOGTOSTDERR \
            $KUBE_LOG_LEVEL \
            $KUBELET_API_SERVER \
            $KUBELET_DNS \
            $KUBELET_DOMAIN \
            $KUBELET_ADDRESS \
            $KUBELET_PORT \
            $KUBELET_HOSTNAME \
            $KUBE_ALLOW_PRIV \
            $KUBELET_ARGS \
            $KUBECONFIG
Restart=on-failure
KillMode=process

[Install]
WantedBy=multi-user.target

When I start the kubelet service I can see the "--cluster-dns=10.254.0.10" parameter is correct set:

root     29705     1  1 13:24 ?        00:00:16 /usr/bin/kubelet --logtostderr=true --v=4 –-cluster-dns=10.254.0.10 --cluster-domain=cluster.local --hostname-override=master --allow-privileged=false --cgroup-driver=systemd --fail-swap-on=false --pod_infra_container_image=177.1.1.35/library/pause:latest --kubeconfig=/root/.kube/config-demo

But when I use systemctl status kubelet check the service the cluster-domain parameter just have only on "-" like:

systemctl status kubelet -l
● kubelet.service - Kubernetes Kubelet Server
   Loaded: loaded (/usr/lib/systemd/system/kubelet.service; enabled; vendor preset: disabled)
   Active: active (running) since Fri 2018-07-13 13:24:07 CST; 5s ago
     Docs: https://github.com/GoogleCloudPlatform/kubernetes
 Main PID: 29705 (kubelet)
   Memory: 30.6M
   CGroup: /system.slice/kubelet.service
           └─29705 /usr/bin/kubelet --logtostderr=true --v=4    -cluster-dns=10.254.0.10 --cluster-domain=cluster.local --hostname-override=master --allow-privileged=false --cgroup-driver=systemd --fail-swap-on=false --pod_infra_container_image=177.1.1.35/library/pause:latest --kubeconfig=/root/.kube/config-demo

In the logs say there is nothing set in cluster-dns flag:

Jul 13 13:24:07 master kubelet: I0713 13:24:07.680625   29705 flags.go:27] FLAG: --cluster-dns="[]"
Jul 13 13:24:07 master kubelet: I0713 13:24:07.680636   29705 flags.go:27] FLAG: --cluster-domain="cluster.local"

The Pods with errors:

pod: "java-deploy-69c84746b9-b2d7j_default(ce02d183-864f-11e8-9bdb-525400c4f6bf)". kubelet does not have ClusterDNS IP configured and cannot create Pod using "ClusterFirst" policy. Falling back to "Default" policy.

My kube-dns config file:

apiVersion: v1
kind: Service
metadata:
  name: kube-dns
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
    kubernetes.io/name: "KubeDNS"
spec:
  selector:
    k8s-app: kube-dns
  clusterIP: 10.254.0.10
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP
---
#apiVersion: v1
#kind: ServiceAccount
#metadata:
#  name: kube-dns
#  namespace: kube-system
#  labels:
#    kubernetes.io/cluster-service: "true"
#    addonmanager.kubernetes.io/mode: Reconcile
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: kube-dns
  namespace: kube-system
  labels:
    addonmanager.kubernetes.io/mode: EnsureExists
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: kube-dns
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
spec:
  # 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:
    rollingUpdate:
      maxSurge: 10%
      maxUnavailable: 0
  selector:
    matchLabels:
      k8s-app: kube-dns
  template:
    metadata:
      labels:
        k8s-app: kube-dns
      annotations:
        scheduler.alpha.kubernetes.io/critical-pod: ''
    spec:
      tolerations:
      - key: "CriticalAddonsOnly"
        operator: "Exists"
      volumes:
      - name: kube-dns-config
        configMap:
          name: kube-dns
          optional: true
      containers:
      - name: kubedns
        image: 177.1.1.35/library/kube-dns:1.14.8
        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:
            memory: 170Mi
          requests:
            cpu: 100m
            memory: 70Mi
        livenessProbe:
          httpGet:
            path: /healthcheck/kubedns
            port: 10054
            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: 3
          timeoutSeconds: 5
        args:
        - --domain=cluster.local.
        - --dns-port=10053
        - --config-dir=/kube-dns-config
        - --kube-master-url=http://177.1.1.40:8080
        - --v=2
        env:
        - name: PROMETHEUS_PORT
          value: "10055"
        ports:
        - containerPort: 10053
          name: dns-local
          protocol: UDP
        - containerPort: 10053
          name: dns-tcp-local
          protocol: TCP
        - containerPort: 10055
          name: metrics
          protocol: TCP
        volumeMounts:
        - name: kube-dns-config
          mountPath: /kube-dns-config
      - name: dnsmasq
        image: 177.1.1.35/library/dnsmasq:1.14.8
        livenessProbe:
          httpGet:
            path: /healthcheck/dnsmasq
            port: 10054
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        args:
        - -v=2
        - -logtostderr
        - -configDir=/etc/k8s/dns/dnsmasq-nanny
        - -restartDnsmasq=true
        - --
        - -k
        - --cache-size=1000
        - --no-negcache
        - --log-facility=-
        - --server=/cluster.local/127.0.0.1#10053
        - --server=/in-addr.arpa/127.0.0.1#10053
        - --server=/ip6.arpa/127.0.0.1#10053
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
        # see: https://github.com/kubernetes/kubernetes/issues/29055 for details
        resources:
          requests:
            cpu: 150m
            memory: 20Mi
        volumeMounts:
        - name: kube-dns-config
          mountPath: /etc/k8s/dns/dnsmasq-nanny
      - name: sidecar
        image: 177.1.1.35/library/sidecar:1.14.8
        livenessProbe:
          httpGet:
            path: /metrics
            port: 10054
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        args:
        - --v=2
        - --logtostderr
        - --probe=kubedns,127.0.0.1:10053,kubernetes.default.svc.cluster.local,5,SRV
        - --probe=dnsmasq,127.0.0.1:53,kubernetes.default.svc.cluster.local,5,SRV
        ports:
        - containerPort: 10054
          name: metrics
          protocol: TCP
        resources:
          requests:
            memory: 20Mi
            cpu: 10m
      dnsPolicy: Default  # Don't use cluster DNS.
      #serviceAccountName: kube-dns

-- frank

centos7

docker

kube-dns

kubernetes

1 Answer

7/16/2018

Recheck your kubelet config:

KUBELET_DNS="–-cluster-dns=10.254.0.10"

It seems to me that the first dash is longer than the second.

Maybe a copy&paste you made causes that strange character. Retype it and retry.

-- Nicola Ben

Source: StackOverflow

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kubelet can not set cluster dns parameter using kube-dns

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