Setup Kubernetes 1.14 Cluster on CentOS 7.6
In this tutorial I will demonstrate how to setup Kubernetes 1.14 Cluster to take advantage of new features that many organizations and community were waiting for. As specially windows containers. Kubernetes now offers windows containers out of the box and allows you to add windows node to Kubernetes cluster.
NOTE: Please make sure swap is disabled on master and worker nodes for Kubernetes setup to be successful. You can follow guide from here.
- Swap is disabled.
- You should know how to install CentOS 7 and knowledge of sudo user.
Master node Tutorial
Let's go ahead and first update our Linux system with all security patches or any other upgrades that will be ensure our system is up-to-date.
sudo yum update -y
After your system has been update, we are now ready to setup Kubernetes cluster. We will first setup docker and then setup Kubernetes.
Install and setup Master and Worker Nodes
Please ensure you have applied following steps to both master and worker node before moving on to steps specific to each nodes. Below steps are common for both master and worker nodes.
Install and Setup Docker
Execute below command to install
sudo yum install -y docker
Now we need to enable and start Docker as a service.
sudo systemctl enable docker && sudo systemctl start docker
To verify if you have docker version 1.13 and higher, execute below command.
sudo docker version
Install Kubernetes packages
In order to grab latest package for Kubernetes, we need to configure our yum repository. Copy and page below line of code to create new config file for Kubernetes yum repo.
sudo bash -c '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 exclude=kube* EOF'
Disable SELinux to prevent any communication issues on all the nodes.
sudo setenforce 0 sudo sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config
sudo yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
After the installation is completed, let's enable
kubelet as a service.
sudo systemctl enable kubelet && sudo systemctl start kubelet
Master node setup
Allow 6443 and 10250 from
firewalld on master node
sudo firewall-cmd --permanent --add-port=6443/tcp && sudo firewall-cmd --permanent --add-port=10250/tcp && sudo firewall-cmd --reload
NOTE: If you do not execute above commands, you would see below warning during Kubernetes initialization.
[WARNING Firewalld]: firewalld is active, please ensure ports [6443 10250] are open or your cluster may not function correctly
error execution phase preflight: [preflight] Some fatal errors occurred:
Set IPTables settings
Copy and paste below line of code on your master and worker node.
sudo bash -c 'cat <<EOF > /etc/sysctl.d/k8s.conf net.bridge.bridge-nf-call-ip6tables = 1 net.bridge.bridge-nf-call-iptables = 1 EOF'
Apply changes by execute below command.
sudo sysctl --system
sudo lsmod | grep br_netfilter
Configure Kubernetes Master node
Now that we are done installing required packages and configuration of your system. Lets go ahead and start the configuration.
First we we need to get all the images that are going to be used during kubernetes initialization. It is optional and kubeadm will automatically pull it during initialization. But I recommend it to first get the images so you don't have to worry about images.
sudo kubeadm config images pull
After it is pulled all the images let's get started with cluster setup.
sudo kubeadm init --pod-network-cidr=10.244.0.0/16
During the initialization, if you received following error that means you did'nt disable your swap. Please go ahead and disable swap and reboot your system and try again.
[ERROR Swap]: running with swap on is not supported. Please disable swap
[preflight] If you know what you are doing, you can make a check non-fatal with
Or, if you received below error, ensure you have applied correct IPTable settings as provided above.
[ERROR FileContent--proc-sys-net-bridge-bridge-nf-call-iptables]: /proc/sys/net/bridge/bridge-nf-call-iptables contents are not set to 1
[preflight] If you know what you are doing, you can make a check non-fatal with
After you have successfully setup your Kubernetes cluster, your output should look similar to below. Please make a note of the key for joining worker nodes to Kubernetes cluster.
[init] Using Kubernetes version: v1.14.0 [preflight] Running pre-flight checks [WARNING Firewalld]: firewalld is active, please ensure ports [6443 10250] are open or your cluster may not function correctly [preflight] Pulling images required for setting up a Kubernetes cluster [preflight] This might take a minute or two, depending on the speed of your internet connection [preflight] You can also perform this action in beforehand using 'kubeadm config images pull' [kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env" [kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml" [kubelet-start] Activating the kubelet service [certs] Using certificateDir folder "/etc/kubernetes/pki" [certs] Generating "ca" certificate and key [certs] Generating "apiserver" certificate and key [certs] apiserver serving cert is signed for DNS names [k8s-master-node kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.0.120] [certs] Generating "apiserver-kubelet-client" certificate and key [certs] Generating "etcd/ca" certificate and key [certs] Generating "etcd/server" certificate and key [certs] etcd/server serving cert is signed for DNS names [k8s-master-node localhost] and IPs [192.168.0.120 127.0.0.1 ::1] [certs] Generating "etcd/peer" certificate and key [certs] etcd/peer serving cert is signed for DNS names [k8s-master-node localhost] and IPs [192.168.0.120 127.0.0.1 ::1] [certs] Generating "etcd/healthcheck-client" certificate and key [certs] Generating "apiserver-etcd-client" certificate and key [certs] Generating "front-proxy-ca" certificate and key [certs] Generating "front-proxy-client" certificate and key [certs] Generating "sa" key and public key [kubeconfig] Using kubeconfig folder "/etc/kubernetes" [kubeconfig] Writing "admin.conf" kubeconfig file [kubeconfig] Writing "kubelet.conf" kubeconfig file [kubeconfig] Writing "controller-manager.conf" kubeconfig file [kubeconfig] Writing "scheduler.conf" kubeconfig file [control-plane] Using manifest folder "/etc/kubernetes/manifests" [control-plane] Creating static Pod manifest for "kube-apiserver" [control-plane] Creating static Pod manifest for "kube-controller-manager" [control-plane] Creating static Pod manifest for "kube-scheduler" [etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests" [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 [apiclient] All control plane components are healthy after 16.501860 seconds [upload-config] storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace [kubelet] Creating a ConfigMap "kubelet-config-1.14" in namespace kube-system with the configuration for the kubelets in the cluster [upload-certs] Skipping phase. Please see --experimental-upload-certs [mark-control-plane] Marking the node k8s-master-node as control-plane by adding the label "node-role.kubernetes.io/master=''" [mark-control-plane] Marking the node k8s-master-node as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule] [bootstrap-token] Using token: 3j2pkk.xk7tnltycyz2xh5n [bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles [bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials [bootstrap-token] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token [bootstrap-token] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster [bootstrap-token] creating the "cluster-info" ConfigMap in the "kube-public" namespace [addons] Applied essential addon: CoreDNS [addons] Applied essential addon: kube-proxy Your Kubernetes control-plane has initialized successfully! To start using your cluster, you need to run the following as a regular user: mkdir -p $HOME/.kube sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config You should now deploy a pod network to the cluster. Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at: https://kubernetes.io/docs/concepts/cluster-administration/addons/ Then you can join any number of worker nodes by running the following on each as root: kubeadm join 192.168.0.120:6443 --token khm95w.mo0wwenu2o9hglls \ --discovery-token-ca-cert-hash sha256:aeb0ca593b63c8d674719858fd2397825825cebc552e3c165f00edb9671d6e32
Adding cluster settings to regular user to be able to access Kubernetes cluster locally.
mkdir -p $HOME/.kube sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config
Apply network settings for pods
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/a70459be0084506e4ec919aa1c114638878db11b/Documentation/kube-flannel.yml
Thats it! You have your master node setup.
Worker node setup
If you have more then one node, apply below steps to each worker nodes.
Use the information received from your master node to join the cluster. Below information may be different for you.
sudo kubeadm join 192.168.0.120:6443 --token khm95w.mo0wwenu2o9hglls \ --discovery-token-ca-cert-hash sha256:aeb0ca593b63c8d674719858fd2397825825cebc552e3c165f00edb9671d6e32
If you receive following output. That means you have successfully connected to kubernetes master node.
[preflight] Running pre-flight checks [preflight] Reading configuration from the cluster... [preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml' [kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.14" ConfigMap in the kube-system namespace [kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml" [kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env" [kubelet-start] Activating the kubelet service [kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap... This node has joined the cluster: * Certificate signing request was sent to apiserver and a response was received. * The Kubelet was informed of the new secure connection details. Run 'kubectl get nodes' on the control-plane to see this node join the cluster.
To check if your node joined the cluster, execute below command from master node.
kubectl get nodes
Your output should look something like below.
NAME STATUS ROLES AGE VERSION k8s-master-node NotReady master 37m v1.14.0 k8s-worker-node-1 NotReady <none> 8m19s v1.14.0
Troubleshooting Master node issues
If you are receive
coredns as shown below, it is likely your firewalld on worker node is blocking connectivity with the master node.
[rahil@k8s-master-node ~]$ kubectl get pods -A -o wide NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES kube-system coredns-fb8b8dccf-9jd8r 0/1 CrashLoopBackOff 15 19h 10.244.1.7 k8s-worker-node-1 <none> <none> kube-system coredns-fb8b8dccf-kfjsz 0/1 CrashLoopBackOff 15 19h 10.244.1.6 k8s-worker-node-1 <none> <none>
Recommended solution is to stop firewalld completely to resolve this issue. Execute below commandto stop firewalld on your worker nodes.
sudo systemctl disable firewalld && sudo systemctl stop firewalld && sudo systemctl status firewalld
[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. Unfortunately, an error has occurred: timed out waiting for the condition This error is likely caused by: - The kubelet is not running - The kubelet is unhealthy due to a misconfiguration of the node in some way (required cgroups disabled) If you are on a systemd-powered system, you can try to troubleshoot the error with the following commands: - 'systemctl status kubelet' - 'journalctl -xeu kubelet' Additionally, a control plane component may have crashed or exited when started by the container runtime. To troubleshoot, list all containers using your preferred container runtimes CLI, e.g. docker. Here is one example how you may list all Kubernetes containers running in docker: - 'docker ps -a | grep kube | grep -v pause' Once you have found the failing container, you can inspect its logs with: - 'docker logs CONTAINERID'
If your master node setup wasn't successful and you are seeing above errors, I recommend starting all over again. I spent several hours and ended up reimaging my VM and reconfigured all of it step by step. Good luck!
Optional but recommended to setup Kubernetes dashboard
From master node execute below command to create new deployment for Kubernetes dashboard. You can also reference it from their github site as well for more information.
kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v1.10.1/src/deploy/recommended/kubernetes-dashboard.yaml