Gist // Install Kubernetes with Flannel Network Plugin on CentOS 7
Install Prerequisites on ALL (Worker and Master) Nodes
Let’s remove any old versions of Docker if they exist:
$ sudo yum remove docker \ docker-common \ docker-selinux \ docker-engine
And let’s (re)install a fresh copy of Docker:
$ yum install docker
We will also need to install the latest release of kubectl, which is used to control Kubernetes. The instructions are straight from https://kubernetes.io/docs/tasks/tools/install-kubectl/
$ curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl
Make it executable:
$ chmod +x ./kubectl
And pop it into the PATH:
$ sudo mv ./kubectl /usr/local/bin/kubectl
Install kubelet and kubeadm on ALL (Worker and Master) Nodes
This is straight from https://kubernetes.io/docs/setup/independent/install-kubeadm/
$ sudo 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 $ sudo setenforce 0 $ sudo yum install -y kubelet kubeadm $ sudo systemctl enable kubelet && systemctl start kubelet
Typically, you would need to install the CNI packages, but they’re already installed in this case.
Configure Kubernetes Master
On the master node, we want to run:
$ sudo kubeadm init --pod-network-cidr=10.244.0.0/16
--pod-network-cidr=10.244.0.0/16 option is a requirement for Flannel - don’t change that network address!
Save the command it gives you to join nodes in the cluster, but we don’t want to do that just yet. You should see a message like
You can now join any number of machines by running the following on each node as root: kubeadm join --token <token> <IP>:6443
Start the cluster as a normal user. This part, I realized, was pretty important as it doesn’t like to play well when you do it as root.
$ sudo cp /etc/kubernetes/admin.conf $HOME/ $ sudo chown $(id -u):$(id -g) $HOME/admin.conf $ export KUBECONFIG=$HOME/admin.conf
Install Flannel for the Pod Network (On Master Node)
We need to install the pod network before the cluster can come up. As such we want to install the latest yaml file that flannel provides. Most installations will use the following:
$ kubectl apply -f https://github.com/coreos/flannel/raw/master/Documentation/kube-flannel.yml
At this point, give it a minute, and have a look at the status of the cluster. run
$ kubectl get pods --all-namespaces and see what it comes back with. If everything shows running, then you’re in business! Otherwise, if you notice errors like:
NAMESPACE NAME READY STATUS RESTARTS AGE ... kube-system kube-flannel-ds-knq4b 1/2 Error 5 3m ...
NAMESPACE NAME READY STATUS RESTARTS AGE ... kube-system kube-flannel-ds-knq4b 1/2 CrashLoopBackOff 5 5m ...
If this is the case, you will need to run the RBAC module as well:
$ kubectl create -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel-rbac.yml
Add Worker Nodes to the Cluster
Upto this point, we haven’t really touched the worker nodes (other than installing the prerequisites), but now you can join the worker nodes by running the command that was given to us when we created the cluster
$ sudo kubeadm join --token <token> <ip>:6443
We’ll see more services spinning up on other services by running
$ kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE kube-system kube-flannel-ds-fldtn 0/2 Pending 0 3s kube-system kube-proxy-c8s32 0/1 Pending 0 3s
And to confirm, when we do a
$ kubectl get nodes, we should see something like:
NAME STATUS AGE VERSION server1 Ready 46m v1.7.0 server2 Ready 3m v1.7.0 server3 Ready 2m v1.7.0
Running Workloads on the Master Node
By default, no workloads will run on the master node. You usually want this in a production environment. In my case, since I’m using it for development and testing, I want to allow containers to run on the master node as well. This is done by a process called “tainting” the host.
On the master, we can run the command
$ kubectl taint nodes --all node-role.kubernetes.io/master- and allow the master to run workloads as well.