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Question

Cannot join a kubernetes cluster

12/20/2018

I have a kubeadm deployed master (v1.10.12) and I'm trying to add a new node to the cluster:

on the master I do:

sudo kubeadm token create
sudo kubeadm token list
TOKEN                     TTL       EXPIRES                USAGES                   DESCRIPTION   EXTRA GROUPS
2txs62.83q81hpici7a0u5q   23h       2018-12-20T23:37:46Z   authentication,signing   <none>        system:bootstrappers:kubeadm:default-node-token

and then on the new node, I run:

sudo yum install -y kubeadm-1.10.12-0
sudo yum install -y kubelet-1.10.12-0

sudo kubeadm reset

sudo kubeadm join --token 2txs62.83q81hpici7a0u5q W.X.Y.Z:6443 --discovery-token-unsafe-skip-ca-verification
[preflight] Running pre-flight checks
[discovery] Trying to connect to API Server "W.X.Y.Z:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://W.X.Y.Z:6443"
[discovery] Cluster info signature and contents are valid and no TLS pinning was specified, will use API Server "W.X.Y.Z:6443"
[discovery] Successfully established connection with API Server "W.X.Y.Z:6443"
[join] Reading configuration from the cluster...
[join] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
unable to fetch the kubeadm-config ConfigMap: failed to get config map: configmaps "kubeadm-config" is forbidden: User "system:bootstrap:2txs62" cannot get configmaps in the namespace "kube-system"

on the master:

kubectl -n kube-system get cm kubeadm-config -oyaml
apiVersion: v1
data:
  MasterConfiguration: |
    api:
      advertiseAddress: W.X.Y.Z
      bindPort: 6443
      controlPlaneEndpoint: ""
    auditPolicy:
      logDir: /var/log/kubernetes/audit
      logMaxAge: 2
      path: ""
    authorizationModes:
    - Node
    - RBAC
    certificatesDir: /etc/kubernetes/pki
    cloudProvider: ""
    criSocket: /var/run/dockershim.sock
    etcd:
      caFile: ""
      certFile: ""
      dataDir: /var/lib/etcd
      endpoints: null
      image: ""
      keyFile: ""
    imageRepository: gcr.io/google_containers
    kubeProxy:
      config:
        bindAddress: 0.0.0.0
        clientConnection:
          acceptContentTypes: ""
          burst: 10
          contentType: application/vnd.kubernetes.protobuf
          kubeconfig: /var/lib/kube-proxy/kubeconfig.conf
          qps: 5
        clusterCIDR: ""
        configSyncPeriod: 15m0s
        conntrack:
          max: null
          maxPerCore: 32768
          min: 131072
          tcpCloseWaitTimeout: 1h0m0s
          tcpEstablishedTimeout: 24h0m0s
        enableProfiling: false
        featureGates:
          "": false
        healthzBindAddress: 0.0.0.0:10256
        hostnameOverride: ""
        iptables:
          masqueradeAll: false
          masqueradeBit: 14
          minSyncPeriod: 0s
          syncPeriod: 30s
        ipvs:
          minSyncPeriod: 0s
          scheduler: ""
          syncPeriod: 30s
        metricsBindAddress: 127.0.0.1:10249
        mode: ""
        nodePortAddresses: null
        oomScoreAdj: -999
        portRange: ""
        resourceContainer: /kube-proxy
        udpIdleTimeout: 250ms
    kubeletConfiguration: {}
    kubernetesVersion: v1.10.12
    networking:
      dnsDomain: cluster.local
      podSubnet: ""
      serviceSubnet: 10.96.0.0/12
    nodeName: kube-master.novalocal
    privilegedPods: false
    token: ""
    tokenGroups:
    - system:bootstrappers:kubeadm:default-node-token
    tokenTTL: 24h0m0s
    tokenUsages:
    - signing
    - authentication
    unifiedControlPlaneImage: ""
kind: ConfigMap
metadata:
  creationTimestamp: 2018-03-28T06:37:58Z
  name: kubeadm-config
  namespace: kube-system
  resourceVersion: "105798137"
  selfLink: /api/v1/namespaces/kube-system/configmaps/kubeadm-config
  uid: 8dc493f2-3252-11e8-a270-fa163e21c438

Help!? cheers,

-- yee379

configmap

join

kubeadm

kubernetes

1 Answer

12/20/2018

Sounds like you have a version mismatch and running into something like this.

You can manually try to create a Role in the kube-system namespace with the name kubeadm:kubeadm-config. For example:

cat <<EOF | kubectl apply -f -
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  namespace: kube-system
  name: kubeadm:kubeadm-config
rules:
- apiGroups:
  - ""
  resourceNames:
  - kubeadm-config
  resources:
  - configmaps
  verbs:
  - get
EOF

and then create a matching RoleBinding:

cat <<EOF | kubectl apply -f -
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  namespace: kube-system
  name: kubeadm:kubeadm-config
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: kubeadm:kubeadm-config
subjects:
- apiGroup: rbac.authorization.k8s.io
  kind: Group
  name: system:nodes
- apiGroup: rbac.authorization.k8s.io
  kind: Group
  name: system:bootstrappers:kubeadm:default-node-token
EOF

-- Rico

Source: StackOverflow

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Cannot join a kubernetes cluster

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