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Installing kubeadm

This page shows how to install the kubeadm toolbox. For information how to create a cluster with kubeadm once you have performed this installation process, see the Using kubeadm to Create a Cluster page.

Before you begin

Verify the MAC address and product_uuid are unique for every node

It is very likely that hardware devices will have unique addresses, although some virtual machines may have identical values. Kubernetes uses these values to uniquely identify the nodes in the cluster. If these values are not unique to each node, the installation process may fail.

Check network adapters

If you have more than one network adapter, and your Kubernetes components are not reachable on the default route, we recommend you add IP route(s) so Kubernetes cluster addresses go via the appropriate adapter.

Check required ports

Master node(s)

Protocol Direction Port Range Purpose
TCP Inbound 6443* Kubernetes API server
TCP Inbound 2379-2380 etcd server client API
TCP Inbound 10250 Kubelet API
TCP Inbound 10251 kube-scheduler
TCP Inbound 10252 kube-controller-manager
TCP Inbound 10255 Read-only Kubelet API

Worker node(s)

Protocol Direction Port Range Purpose
TCP Inbound 10250 Kubelet API
TCP Inbound 10255 Read-only Kubelet API
TCP Inbound 30000-32767 NodePort Services**

** Default port range for NodePort Services.

Any port numbers marked with * are overridable, so you will need to ensure any custom ports you provide are also open.

Although etcd ports are included in master nodes, you can also host your own etcd cluster externally or on custom ports.

The pod network plugin you use (see below) may also require certain ports to be open. Since this differs with each pod network plugin, please see the documentation for the plugins about what port(s) those need.

Installing Docker

On each of your machines, install Docker. Version 17.03 is recommended, but 1.11, 1.12 and 1.13 are known to work as well. Versions 17.06+ might work, but have not yet been tested and verified by the Kubernetes node team. Keep track of the latest verified Docker version in the Kubernetes release notes.

Please proceed with executing the following commands based on your OS as root. You may become the root user by executing sudo -i after SSH-ing to each host.

If you already have the required versions of the Docker installed, you can move on to next section. If not, you can use the following commands to install Docker on your system:

Install Docker from Ubuntu’s repositories:

apt-get update
apt-get install -y docker.io

or install Docker CE 17.03 from Docker’s repositories for Ubuntu or Debian:

apt-get update
apt-get install -y apt-transport-https ca-certificates curl software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add -
add-apt-repository "deb https://download.docker.com/linux/$(. /etc/os-release; echo "$ID") $(lsb_release -cs) stable"
apt-get update && apt-get install -y docker-ce=$(apt-cache madison docker-ce | grep 17.03 | head -1 | awk '{print $3}')

Install Docker using your operating system’s bundled package:

yum install -y docker
systemctl enable docker && systemctl start docker

Enable and start Docker:

systemctl enable docker && systemctl start docker

Refer to the official Docker installation guides for more information.

Installing kubeadm, kubelet and kubectl

You will install these packages on all of your machines:

kubeadm will not install or manage kubelet or kubectl for you, so you will need to ensure they match the version of the Kubernetes control panel you want kubeadm to install for you. If you do not, there is a risk of a version skew occurring that can lead to unexpected, buggy behaviour. However, one minor version skew between the kubelet and the control plane is supported, but the kubelet version may never exceed the API server version. For example, kubelets running 1.7.0 should be fully compatible with a 1.8.0 API server, but not vice versa.

For more information on version skews, please read our version skew policy.

apt-get update && apt-get install -y apt-transport-https curl
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
deb http://apt.kubernetes.io/ kubernetes-xenial main
EOF
apt-get update
apt-get install -y kubelet kubeadm kubectl

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
setenforce 0
yum install -y kubelet kubeadm kubectl
systemctl enable kubelet && systemctl start kubelet

Note:

  • Disabling SELinux by running setenforce 0 is required to allow containers to access the host filesystem, which is required by pod networks for example. You have to do this until SELinux support is improved in the kubelet.

  • Some users on RHEL/CentOS 7 have reported issues with traffic being routed incorrectly due to iptables being bypassed. You should ensure net.bridge.bridge-nf-call-iptables is set to 1 in your sysctl config, e.g.

    cat <<EOF >  /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system

Install CNI plugins (required for most pod network):

CNI_VERSION="v0.6.0"
mkdir -p /opt/cni/bin
curl -L "https://github.com/containernetworking/plugins/releases/download/${CNI_VERSION}/cni-plugins-amd64-${CNI_VERSION}.tgz" | tar -C /opt/cni/bin -xz

Install kubeadm, kubelet, kubectl and add a kubelet systemd service:

RELEASE="$(curl -sSL https://dl.k8s.io/release/stable.txt)"

mkdir -p /opt/bin
cd /opt/bin
curl -L --remote-name-all https://storage.googleapis.com/kubernetes-release/release/${RELEASE}/bin/linux/amd64/{kubeadm,kubelet,kubectl}
chmod +x {kubeadm,kubelet,kubectl}

curl -sSL "https://raw.githubusercontent.com/kubernetes/kubernetes/${RELEASE}/build/debs/kubelet.service" | sed "s:/usr/bin:/opt/bin:g" > /etc/systemd/system/kubelet.service
mkdir -p /etc/systemd/system/kubelet.service.d
curl -sSL "https://raw.githubusercontent.com/kubernetes/kubernetes/${RELEASE}/build/debs/10-kubeadm.conf" | sed "s:/usr/bin:/opt/bin:g" > /etc/systemd/system/kubelet.service.d/10-kubeadm.conf

Enable and start kubelet:

systemctl enable kubelet && systemctl start kubelet

The kubelet is now restarting every few seconds, as it waits in a crashloop for kubeadm to tell it what to do.

Configure cgroup driver used by kubelet on Master Node

Make sure that the cgroup driver used by kubelet is the same as the one used by Docker. Verify that your Docker cgroup driver matches the kubelet config:

docker info | grep -i cgroup
cat /etc/systemd/system/kubelet.service.d/10-kubeadm.conf

If the Docker cgroup driver and the kubelet config don’t match, change the kubelet config to match the Docker cgroup driver. The flag you need to change is --cgroup-driver. If it’s already set, you can update like so:

sed -i "s/cgroup-driver=systemd/cgroup-driver=cgroupfs/g" /etc/systemd/system/kubelet.service.d/10-kubeadm.conf

Otherwise, you will need to open the systemd file and add the flag to an existing environment line.

Then restart kubelet:

systemctl daemon-reload
systemctl restart kubelet

Troubleshooting

If you are running into difficulties with kubeadm, please consult our troubleshooting docs.

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