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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
• Check network adapters
• Check required ports
• Installing Docker
• Installing kubeadm, kubelet and kubectl
• Configure cgroup driver used by kubelet on Master Node
• Troubleshooting
• What's next

Before you begin

• One or more machines running one of:
  • Ubuntu 16.04+
  • Debian 9
  • CentOS 7
  • RHEL 7
  • Fedora 25/26 (best-effort)
  • HypriotOS v1.0.1+
  • Container Linux (tested with 1800.6.0)
• 2 GB or more of RAM per machine (any less will leave little room for your apps)
• 2 CPUs or more
• Full network connectivity between all machines in the cluster (public or private network is fine)
• Unique hostname, MAC address, and product_uuid for every node. See here for more details.
• Certain ports are open on your machines. See here for more details.
• Swap disabled. You MUST disable swap in order for the kubelet to work properly.

Verify the MAC address and product_uuid are unique for every node

• You can get the MAC address of the network interfaces using the command ip link or ifconfig -a
• The product_uuid can be checked by using the command sudo cat /sys/class/dmi/id/product_uuid

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)

Worker node(s)

** 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:

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

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}')

yum install -y docker
systemctl enable docker && systemctl 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: the command to bootstrap the cluster.

• kubelet: the component that runs on all of the machines in your cluster and does things like starting pods and containers.

• kubectl: the command line util to talk to your cluster.

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.

These instructions exclude all Kubernetes packages from any system upgrades. This is because kubeadm and Kubernetes require special attention to upgrade.

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
apt-mark hold 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
exclude=kube*
EOF
setenforce 0
yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
systemctl enable kubelet && systemctl start kubelet

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

CRICTL_VERSION="v1.11.1"
mkdir -p /opt/bin
curl -L "https://github.com/kubernetes-incubator/cri-tools/releases/download/${CRICTL_VERSION}/crictl-${CRICTL_VERSION}-linux-amd64.tar.gz" | tar -C /opt/bin -xz

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

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

When using Docker, kubeadm will automatically detect the cgroup driver for the kubelet and set it in the /var/lib/kubelet/kubeadm-flags.env file during runtime.

If you are using a different CRI, you have to modify the file /etc/default/kubelet with your cgroup-driver value, like so:

KUBELET_KUBEADM_EXTRA_ARGS=--cgroup-driver=<value>

This file will be used by kubeadm init and kubeadm join to source extra user defined arguments for the kubelet.

Please mind, that you only have to do that if the cgroup driver of your CRI is not cgroupfs, because that is the default value in the kubelet already.

Restarting the kubelet is required:

systemctl daemon-reload
systemctl restart kubelet

Troubleshooting

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

What's next

• Using kubeadm to Create a Cluster