How to Install a Kubernetes Cluster on CentOS 7

Donated by Google to the Opensource community, Kubernetes has now become the container management tool of choice. It can manage and orchestrate not just docker runtimes but also Containers and Rkt runtimes.

A typical Kubernetes cluster would generally have a master node and several worker-nodes or Minions. The worker-nodes are then managed from the master node, thus ensuring that the cluster is managed from a central point.

It’s also important to mention that you can also deploy a single-node Kubernetes cluster which is generally recommended for very light, non-production workloads. For this, you can use Minikube, which is a tool that runs a single-node Kubernetes cluster in a virtual machine on your node.

Recommended Read: How to Install a Kubernetes Cluster on CentOS 8

For this tutorial, we will walk-through a multi-node Kubernetes cluster installation on CentOS 7 Linux. This tutorial is command-line based so you will need access to your terminal window.

Prerequisites

  1. Multiple servers running Centos 7 (1 Master Node, 2 Worker Nodes). It is recommended that your Master Node have at least 2 CPUs, though this is not a strict requirement.
  2. Internet connectivity on all your nodes. We will be fetching Kubernetes and docker packages from the repository. Equally, you will need to make sure that the yum package manager is installed by default and can fetch packages remotely.
  3. You will also need access to an account with sudo or root privileges. In this tutorial, I will be using my root account.

Our 3-node cluster will look something like this:

Kubernetes Cluster Diagram
Kubernetes Cluster Diagram

Installation of Kubernetes Cluster on Master-Node

For Kubernetes to work, you will need a containerization engine. For this installation, we will use docker as it is the most popular.

The following steps will run on the Master-Node.

Step 1: Prepare Hostname, Firewall and SELinux

On your master node, set the hostname and if you don’t have a DNS server, then also update your /etc/hosts file.

# hostnamectl set-hostname master-node
# cat <<EOF>> /etc/hosts
10.128.0.27 master-node
10.128.0.29 node-1 worker-node-1
10.128.0.30 node-2 worker-node-2
EOF

You can ping worker-node-1 and worker-node-2 to test if your updated hostfile is fine using ping command.

# ping 10.128.0.29
# ping 10.128.0.30

Next, disable SElinux and update your firewall rules.

# setenforce 0
# sed -i --follow-symlinks 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux
# reboot

Set the following firewall rules on ports. Make sure that each firewall-cmd command, returns a success.

# firewall-cmd --permanent --add-port=6443/tcp
# firewall-cmd --permanent --add-port=2379-2380/tcp
# firewall-cmd --permanent --add-port=10250/tcp
# firewall-cmd --permanent --add-port=10251/tcp
# firewall-cmd --permanent --add-port=10252/tcp
# firewall-cmd --permanent --add-port=10255/tcp
# firewall-cmd –reload
# modprobe br_netfilter
# echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables

Step 2: Setup the Kubernetes Repo

You will need to add Kubernetes repositories manually as they do not come installed by default on CentOS 7.

cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF

Step 3: Install Kubeadm and Docker

With the package repo now ready, you can go ahead and install kubeadm and docker packages.

# yum install kubeadm docker -y 

When the installation completes successfully, enable and start both services.

# systemctl enable kubelet
# systemctl start kubelet
# systemctl enable docker
# systemctl start docker

Step 4: Initialize Kubernetes Master and Setup Default User

Now we are ready to initialize kubernetes master, but before that you need to disable swap in order to run “kubeadm init“ command.

# swapoff -a

Initializing Kubernetes master is a fully automated process that is managed by the “kubeadm init“ command which you will run.

# kubeadm init
Initialize Kubernetes Master
Initialize Kubernetes Master

You may want to copy the last line and save it somewhere because you will need to run it on the worker nodes.

kubeadm join 10.128.0.27:6443 --token nu06lu.xrsux0ss0ixtnms5  \ --discovery-token-ca-cert-hash sha256:f996ea3564e6a07fdea2997a1cf8caeddafd6d4360d606dbc82314688425cd41 

Tip: Sometimes this command might complain about the arguments (args) passed, so edit it to avoid any errors. So, you will delete the ‘\’ character accompanying the --token and your final command will look like this.

kubeadm join 10.128.0.27:6443 --token nu06lu.xrsux0ss0ixtnms5  --discovery-token-ca-cert-hash sha256:f996ea3564e6a07fdea2997a1cf8caeddafd6d4360d606dbc82314688425cd41

Having initialized Kubernetes successfully, you will need to allow your user to start using the cluster. In our case, we want to run this installation as root user, therefore we will go ahead and run these commands as root. You can change to a sudo enabled user you prefer and run the below using sudo.

To use root, run:

# mkdir -p $HOME/.kube
# cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
# chown $(id -u):$(id -g) $HOME/.kube/config

To use a sudo enabled user, run:

$ mkdir -p $HOME/.kube
$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
$ sudo chown $(id -u):$(id -g) $HOME/.kube/config

Now check to see if the kubectl command is activated.

# kubectl get nodes
Check Status of Nodes
Check Status of Nodes

At this point, you will also notice that the status of the master-node is ‘NotReady’. This is because we are yet to deploy the pod network to the cluster.

The pod Network is the overlay network for the cluster, that is deployed on top of the present node network. It is designed to allow connectivity across the pod.

Step 5: Setup Your Pod Network

Deploying the network cluster is a highly flexible process depending on your needs and there are many options available. Since we want to keep our installation as simple as possible, we will use Weavenet plugin which does not require any configuration or extra code and it provides one IP address per pod which is great for us. If you want to see more options, please check here.

These commands will be important to get the pod network setup.

# export kubever=$(kubectl version | base64 | tr -d '\n')
# kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$kubever"
Setup Pod Network
Setup Pod Network

Now if you check the status of your master-node, it should be ‘Ready’.

# kubectl get nodes
Check Status of Master Nodes
Check Status of Master Nodes

Next, we add the worker nodes to the cluster.

Setting Up Worker Nodes to Join Kubernetes Cluster

The following steps will run on the worker nodes. These steps should be run on every worker node when joining the Kubernetes cluster.

Step 1: Prepare Hostname, Firewall and SELinux

On your worker-node-1 and worker-node-2, set the hostname and in case you don’t have a DNS server, then also update your master and worker nodes on /etc/hosts file.

# hostnamectl set-hostname 'node-1'
# cat <<EOF>> /etc/hosts
10.128.0.27 master-node
10.128.0.29 node-1 worker-node-1
10.128.0.30 node-2 worker-node-2
EOF

You can ping master-node to test if your updated hostfile is fine.

Next, disable SElinux and update your firewall rules.

# setenforce 0
# sed -i --follow-symlinks 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux

Set the following firewall rules on ports. Make sure that all firewall-cmd commands, return success.

# firewall-cmd --permanent --add-port=6783/tcp
# firewall-cmd --permanent --add-port=10250/tcp
# firewall-cmd --permanent --add-port=10255/tcp
# firewall-cmd --permanent --add-port=30000-32767/tcp
# firewall-cmd  --reload
# echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables

Step 2: Setup the Kubernetes Repo

You will need to add Kubernetes repositories manually as they do not come pre-installed on CentOS 7.

cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF

Step 3: Install Kubeadm and Docker

With the package repo now ready, you can go ahead and install kubeadm and docker packages.

# yum install kubeadm docker -y 

Start and enable both the services.

# systemctl enable docker
# systemctl start docker
# systemctl enable kubelet
# systemctl start kubelet

Step 4: Join the Worker Node to the Kubernetes Cluster

We now require the token that kubeadm init generated, to join the cluster. You can copy and paste it to your node-1 and node-2 if you had copied it somewhere.

# kubeadm join 10.128.0.27:6443 --token nu06lu.xrsux0ss0ixtnms5  --discovery-token-ca-cert-hash sha256:f996ea3564e6a07fdea2997a1cf8caeddafd6d4360d606dbc82314688425cd41 
Join Nodes to Kubernets Cluster
Join Nodes to Kubernets Cluster

As suggested on the last line, go back to your master-node and check if worker node-1 and worker node-2 have joined the cluster using the following command.

# kubectl get nodes
Check All Nodes Status in Kubernetes Cluster
Check All Nodes Status in Kubernetes Cluster

If all the steps run successfully, then, you should see node-1 and node-2 in ready status on the master-node.

Recommended Read: How to Deploy Nginx on a Kubernetes Cluster

At this point, we have successfully completed an installation of a Kubernetes cluster on Centos 7 and we have successfully on-boarded two worker-nodes. You can now begin to create your pods and deploy your services.

Kioie Eddy
Work as a Cloud Architect in Nairobi, Kenya. Spend my time designing Cloud and DevOps architectures with a focus on Opensource. Also a contributor to several Opensource projects.

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47 thoughts on “How to Install a Kubernetes Cluster on CentOS 7”

  1. Good Afternoon,

    At step 3: # yum install kubeadm docker -y

    There is such an error:

    Loaded plugins: fastestmirror, langpacks
    Loading mirror speeds from cached hostfile
     * base: mirror.nsc.liu.se
     * extras: mirror.nsc.liu.se
     * updates: mirror.nsc.liu.se
    base                                                                                                                       | 3.6 kB  00:00:00
    extras                                                                                                                     | 2.9 kB  00:00:00
    https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64/repodata/repomd.xml: [Errno 14] HTTPS Error 403 - Forbidden
    Trying other mirror.
    To address this issue please refer to the below wiki article
    
    https://wiki.centos.org/yum-errors
    

    Help how to solve this issue, thank you.

    Reply
    • @Tim,

      The error message you’re encountering indicates that there is an issue with accessing the repository for Kubernetes, but when I tried the repository it is accessible.

      https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64/repodata/repomd.xml
      

      It seems some temporary issues with the URL which can cause such errors. I suggest you retry the command to see if the issue persists.

      # yum install kubeadm docker -y
      
      Reply
  2. Containerd – it is required after step 3.

    # yum install -y yum-utils
    # yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
    # yum install -y containerd.io
    # mkdir -p /etc/containerd
    # containerd config default | sudo tee /etc/containerd/config.toml
    # systemctl restart contained
    

    Disable Firewall – no need to do all steps given in step 2 for firewall – use my firewall things.

    $ sudo systemctl stop firewalld
    $ sudo systemctl disable firewalld
    $ sudo systemctl mask --now firewalls
    

    Worker node –

    # swapoff -a
    
    Reply
    • Thanks, I was going to add that step and saw it’s already there.

      @tecmint team, I think it’s better to update the page to add this missing part, otherwise it causes confusion and people get stuck at the ‘kubeadm init‘ part.

      Reply
  3. ic/configmaps/cluster-info?timeout=10s”: dial tcp 192.168.0.105:6443: connect: no route to host
    I0626 14:09:49.276307 3305 token.go:217] [discovery] Failed to request cluster-info, will try again: Get “https://192.168.0.105:6443/api/v1/namespaces/kube-public/configmaps/cluster-info?timeout=10s”: dial tcp 192.168.0.105:6443: connect: no route to host
    I0626 14:09:55.694361 3305 token.go:217] [discovery] Failed to request cluster-info, will try again: Get “https://192.168.0.105:6443/api/v1/namespaces/kube-public/configmaps/cluster-info?timeout=10s”: dial tcp 192.168.0.105:6443: connect: no route to host

    Reply
  4. I have followed all the steps but getting this issue.

    Please help me, I was facing this issue for the last 10 days, I am new to Kubernetes.

    Please help me.

    Please find the logs for the same.=
    =======================================================

    [wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory “/etc/kubernetes/manifests”. This can take up to 4m0s
    [kubelet-check] Initial timeout of 40s passed.
    [kubelet-check] It seems like the kubelet isn’t running or healthy.
    [kubelet-check] The HTTP call equal to ‘curl -sSL http://localhost:10248/healthz‘ failed with error: Get “http://localhost:10248/healthz“: dial tcp [::1]:10248: connect: connection refused.

    Reply
  5. I followed the same steps, but getting the following error when joining node to master. Any help would be appreciated.

    [preflight] Running pre-flight checks

    error execution phase preflight: couldn’t validate the identity of the API Server: Get “https://10.0.2.15:6443/api/v1/namespaces/kube-public/configmaps/cluster-info?timeout=10s”: dial tcp 10.0.2.15:6443: connect: connection refused

    To see the stack trace of this error execute with –v=5 or higher

    This is the output of netstat -tulpn command in the master node.
    tcp6 0 0 :::6781 :::* LISTEN 8516/weave-npc
    tcp6 0 0 :::6782 :::* LISTEN 8802/weaver
    tcp6 0 0 :::6783 :::* LISTEN 8802/weaver
    tcp6 0 0 :::10250 :::* LISTEN 6116/kubelet
    tcp6 0 0 :::6443 :::* LISTEN 5867/kube-apiserver
    tcp6 0 0 :::10256 :::* LISTEN 6276/kube-proxy
    tcp6 0 0 :::22 :::* LISTEN 1047/sshd
    tcp6 0 0 ::1:25 :::* LISTEN 1306/master

    Reply
  6. [WARNING IsDockerSystemdCheck]: detected “cgroupfs” as the Docker cgroup driver. The recommended driver is “systemd”. Please follow the guide at https://kubernetes.io/docs/setup/cri/
    error execution phase preflight: couldn’t validate the identity of the API Server: Get “https://172.31.69.32:6443/api/v1/namespaces/kube-public/configmaps/cluster-info?timeout=10s”: dial tcp 172.31.69.32:6443: connect: no route to host

    Reply
  7. All seems to be working fine at first!

    [root@master-node ~]# kubectl get nodes
    NAME          STATUS   ROLES    AGE     VERSION
    master-node   Ready    master   56m     v1.18.5
    node-1        Ready       10m     v1.18.5
    node-2        Ready       9m33s   v1.18.5
    node-3        Ready       12m     v1.18.5
    

    But the DNS resolution is not working:

    [root@master-node ~]# kubectl exec -ti busybox -- nslookup google.com
    Server:    10.96.0.10
    Address 1: 10.96.0.10
    
    nslookup: can't resolve 'google.com'
    command terminated with exit code 1
    

    I followed
    https://v1-16.docs.kubernetes.io/docs/tasks/administer-cluster/dns-debugging-resolution/

    Any ideas?

    Reply
    • After long days of troubleshooting, I ended up with rke and canal instead. DNS queries are resolved without a hitch. Thanks!

      $ kubectl exec -i -t dnsutils -- nslookup google.com
      Server:         10.43.0.10
      Address:        10.43.0.10#53
      
      Non-authoritative answer:
      
      Name:   google.com
      Address: 172.217.16.46
      Name:   google.com
      Address: 2a00:1450:401b:805::200e
      
      Reply
  8. I have Installed Kubernetes by following your guide on AWS ec2 instance and deployed sample HTML application on it.

    Now I want to access my sample app using dns name like app.example.com.

    How can I do that. Any idea?

    Reply
    • Mangesh,

      This is a 2 parts solution.

      Part 1 – Domain:

      • If you have a public domain of your own then you are sorted and you can follow part2, all you have to do is to create A records to the domain on your DNS management.
      • If you do not have a public domain then you will need to use a private domain and force your local workstation to use that DNS server. Like you could set up a local DNS server like dnsmasq and user your laptop to use that before any other DNS IPs.

      All of this is assuming that you are using public IPs on your ec2 instances. if you are using private you will need LB with public IP OR a VPN from your local to AWS which I don’t think you would have considering the expenses in it.

      Part 2 – Accessing the domain:

      • Option 1 – You could use type: LoadBalancer in your service and it creates the LB (provided you gave it the access). And you can point your domain to LB IP and access it. To make it future proof for more domains coming you can even set up ingress-controller with its service as a Load balancer and create ingress for your app. That way not just this but future domains can be all hosted on the same LB saving you money.
      • Option 2 – You could create ingress-controller like Nginx as daemon set instead of deployment and enable the host port and hostIPs. That way it uses node IPs. However this will need to have your nodes public IPs to work.. and then have ingress created. Point your domain to any of the Node IPs and you can access your site.
      • Option 3 – Create your service as type: NodePort and point your domain to any of the node IPs. then go to app.example.com:NODEPORT and you can access your app.

      Part 2 assumes that you have public IPs for your nodes. If that’s not the case Option1 still works., just that you pay for LB.

      Reply
  9. [root@nodetwo ~]# firewall-cmd --permanent --add-port=30000-32767/tcp
    success
    [root@nodetwo ~]# firewall-cmd  --reload
    success
    [root@nodetwo ~]# echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables
    -bash: /proc/sys/net/bridge/bridge-nf-call-iptables: No such file or directory
    

    what is the reason? Please could you help?

    Reply
    • Ran into the same issue, but fixed it with the following command.

      # modprobe br_netfilter
      

      then re-run this:

      # echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables
      
      Reply
  10. Hi, I am getting the below error while doing Kube init.

    [root@adi-dock1 /]# kubeadm init
    W0323 19:50:41.915357 105851 validation.go:28] Cannot validate kube-proxy config – no validator is available
    W0323 19:50:41.915462 105851 validation.go:28] Cannot validate kubelet config – no validator is available
    [init] Using Kubernetes version: v1.17.4
    [preflight] Running pre-flight checks
    [WARNING Firewalld]: firewalld is active, please ensure ports [6443 10250] are open or your cluster may not function correctly
    [WARNING HTTPProxy]: Connection to “https://10.127.200.79” uses proxy “http://72.163.217.40:8080”. If that is not intended, adjust your proxy settings
    [WARNING HTTPProxyCIDR]: connection to “10.96.0.0/12” uses proxy “http://72.163.217.40:8080”. This may lead to malfunctional cluster setup. Make sure that Pod and Services IP ranges specified correctly as exceptions in proxy configuration
    error execution phase preflight: [preflight] Some fatal errors occurred:
    [ERROR FileAvailable–etc-kubernetes-manifests-kube-apiserver.yaml]: /etc/kubernetes/manifests/kube-apiserver.yaml already exists
    [ERROR FileAvailable–etc-kubernetes-manifests-kube-controller-manager.yaml]: /etc/kubernetes/manifests/kube-controller-manager.yaml already exists
    [ERROR FileAvailable–etc-kubernetes-manifests-kube-scheduler.yaml]: /etc/kubernetes/manifests/kube-scheduler.yaml already exists
    [ERROR FileAvailable–etc-kubernetes-manifests-etcd.yaml]: /etc/kubernetes/manifests/etcd.yaml already exists
    [ERROR DirAvailable–var-lib-etcd]: /var/lib/etcd is not empty
    [preflight] If you know what you are doing, you can make a check non-fatal with `–ignore-preflight-errors=…`
    To see the stack trace of this error execute with –v=5 or higher

    Reply
    • Probably you have initiated already it before. Try “kubeadm reset” that should reset everything and you can re-initiate again.

      Reply
  11. @Kioie, Thanks for your great article. I’ve used 3 VMS in Hyper-V to build the cluster. After I completed according to your guide, I got the next information when I run `kubectl get nodes` on a master node.

    The slaves are not ready. When I run `kubectl version` on the slave node, I got a message as ‘The connection to the server localhost:8080 was refused – did you specify the right host or port?’. Could you give me some advice about it? Thanks!

    [root@master-node .kube]# kubectl get nodes
    NAME          STATUS     ROLES    AGE    VERSION
    master-node   Ready      master   126m   v1.17.3
    node-1        NotReady      36m    v1.17.4
    node-2        NotReady      18m    v1.17.4
    
    Reply
    • @cycaky

      That’s very likely due to the weave network pods not running on the worker nodes. On master do ‘kubectl get pods -n kube-system -owide’ and you will see the weave pods on nodes will be struggling. If yes, can you see the pod logs to know what are they struggling with?

      Reply
    • Hi I am stuck in the same place yours there is something missing in the steps else we need to use different network plugin instead of wave-net.

      [root@master-node ~]# kubectl get nodes
      NAME          STATUS     ROLES    AGE   VERSION
      master-node   Ready      master   22h   v1.18.6
      node-1        NotReady      14h   v1.18.6
      node-2        NotReady      14h   v1.18.6
      

      Please let me out.

      RamT

      Reply
      • For me also the same issue.

        [root@k8smaster ~]# kubectl get nodes
        NAME          STATUS     ROLES                  AGE    VERSION
        k8smaster     Ready      control-plane,master   12h    v1.22.1
        k8swornode1   NotReady                    2m7s   v1.22.1
        k8swornode2   NotReady                    102s   v1.22.1
        

        I have to restart the kubelet service and after 2 min all nodes are ready on the master node.

        [root@k8smaster ~]# systemctl restart kubelet.service
        [root@k8smaster ~]# kubectl get nodes
        NAME          STATUS     ROLES                  AGE     VERSION
        k8smaster     NotReady   control-plane,master   12h     v1.22.1
        k8swornode1   Ready                       4m48s   v1.22.1
        k8swornode2   Ready                       4m23s   v1.22.1
        [root@k8smaster ~]# kubectl get nodes
        NAME          STATUS     ROLES                  AGE     VERSION
        k8smaster     NotReady   control-plane,master   12h     v1.22.1
        k8swornode1   Ready                       4m56s   v1.22.1
        k8swornode2   Ready                       4m31s   v1.22.1
        [root@k8smaster ~]# kubectl get nodes
        NAME          STATUS   ROLES                  AGE     VERSION
        k8smaster     Ready    control-plane,master   12h     v1.22.1
        k8swornode1   Ready                     5m10s   v1.22.1
        k8swornode2   Ready                     4m45s   v1.22.1
        [root@k8smaster ~]#
        
        Reply
  12. Hi,

    not sure, why I am getting the below error on node1. though follow the exact steps.

    [root@node1 ~]# kubeadm join 192.168.0.142:6443 --token nkzqbg.fkm4ulii3ub2irsi --discovery-token-ca-cert-hash sha256:795af5d43eb5f6b47df9fd39c3462f0a42ab242aa857019fd6147f0058f80b65
    W0213 20:31:56.839498 4860 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
    [preflight] Running pre-flight checks

    Reply
  13. Please add a comment on your post so that the users also need to add a flag called “fail-to-swap” to FALSE on the /etc/sysconfig/kubelet config file so that the kubelet service may start without any issues on CentOS 7 systemd.

    From:

    KUBELET_EXTRA_ARGS=
    

    TO BE:

    KUBELET_EXTRA_ARGS=--fail-swap-on=false
    

    P.S: This should be done on all servers (Master and Worker Nodes).

    Reply
    • Hi Eduardo, thanks for noticing this. “Fail-swap-on=false” is a temporary measure to allow kubelet to run with swap on, bypassing swap checks. This is not an ideal option to run on, and so it is best not to go that direction.

      I looked at the documentation and tried it on one of the machines, and basically the recommendation is to simply permanently switch off swap and it should take care of all this, including during reboots.

      However, there are other situations where you would need swap on, at least temporarily. I would, therefore, give caution if you do choose to enable this option unless you are sure that is what you want.

      Reply
  14. I am getting below error while joining the worker node to master.

    [root@node01 yum.repos.d]# kubeadm join 10.0.3.15:6443 --token jzwvg4.bzv2b5omdcl3kosl --discovery-token-ca-cert-hash sha256:ada901bfbb4ae0e9d26aaeb54f3794cbb7bfe60f861f90efed1416a490ce041d
    W0130 06:26:26.065050 10134 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
    [preflight] Running pre-flight checks
    error execution phase preflight: couldn’t validate the identity of the API Server: abort connecting to API servers after timeout of 5m0s
    To see the stack trace of this error execute with –v=5 or higher

    Reply
        • Hi Adarsh, DM me on @kioi_e on twitter and I can help troubleshoot.

          This error could be arising from two things:

          1. The discovery token
          2. Connectivity to the master node

          To troubleshoot,

          1. Verify that the discovery token “kubeadm join 10.0.3.15:6443 –token jzwvg4.bzv2b5omdcl3kosl –discovery-token-ca-cert-hash sha256:ada901bfbb4ae0e9d26aaeb54f3794cbb7bfe60f861f90efed1416a490ce041d” is valid. Make sure that you have the full token.
          2. Also make sure that port “10.0.3.15:6443” is accessible and is not blocked by your firewall.
          3. Also, check that your kubectl service is running and your master node is also up and running. You can use the command “kubectl get nodes” to verify.
          Reply
          • Hi Kioie, I have set up the Kubernetes cluster on AWS with 1 master and 3 worker nodes running on Centos 7. I am facing issues while creating statefulset (unable to create persistent storage). Can you help me out?

            PVC fails with ‘Failed to get AWS Cloud Provider. GetCloudProvider returned instead’.
            Thanks.

  15. Thank you for the article it is just about detailed enough for newbies to keep up the good work.

    I am looking forward to more articles.

    Reply
  16. I am following your tutorial to install the Kubernetes cluster.

    I’ve got the error when trying to run “kubeadm init” command.

    From Kubernetes official documentation, I found out that swap must be disabled in order to run “kubeadm init“.

    Please add it to your contents.

    Thank you for sharing your good knowledge with unknowns. :)

    Reply
    • Hi @Simon

      You are right, sometimes swap tends to affect the “kubeadm init“, and it is best to disable it. I will update the article to reflect this. Thanks for your feedback and thanks for reading.

      Reply
  17. I have already configured this cluster but I want to configure master and slave Kubernetes servers with 2 workers node. I also want to access the graphical mode of Kubernetes. Could you please write an article on that.

    • 2 Kubernetes with 2 worker nodes.
    • Graphical GUI of Kubernetes based on IP address, not localhost IP.
    • Create Apache cluster service and how to access them.
    Reply
    • Hello Pankaj, thanks for the question. I can definitely do a follow-up article.

      Just some clarification:

      • When you say 2 Kubernetes with 2 Worker nodes, do you mean 2 Master Nodes and 2 worker nodes? If so, are you talking about a high availability setup?
      • A GUI of Kubernetes based on IP address, do you mean a Kubernetes GUI running on a public IP?
      • An Apache Cluster Service, do you mean An Apache Webserver on a clustered setup?
      Reply
    • @cryptoparty Kubespray is a great tool that can be used to automate the process, but there are many use-cases where a manual install would be necessary, and this tutorial is great as an option.

      Reply

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