Installing kubeadm

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

Before you begin

• A compatible Linux host. The Kubernetes project provides generic instructions for Linux distributions based on Debian and Red Hat, and those distributions without a package manager.
• 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

These required ports need to be open in order for Kubernetes components to communicate with each other. You can use tools like netcat to check if a port is open. For example:

nc 127.0.0.1 6443

The pod network plugin you use 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 a container runtime

To run containers in Pods, Kubernetes uses a container runtime.

By default, Kubernetes uses the Container Runtime Interface (CRI) to interface with your chosen container runtime.

If you don't specify a runtime, kubeadm automatically tries to detect an installed container runtime by scanning through a list of known endpoints.

If multiple or no container runtimes are detected kubeadm will throw an error and will request that you specify which one you want to use.

See container runtimes for more information.

The tables below include the known endpoints for supported operating systems:

• Linux
• Windows

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 plane 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, the kubelet running 1.7.0 should be fully compatible with a 1.8.0 API server, but not vice versa.

For information about installing kubectl, see Install and set up kubectl.

For more information on version skews, see:

• Kubernetes version and version-skew policy
• Kubeadm-specific version skew policy

• Debian-based distributions
• Red Hat-based distributions
• Without a package manager

CNI_PLUGINS_VERSION="v1.1.1"
ARCH="amd64"
DEST="/opt/cni/bin"
sudo mkdir -p "$DEST"
curl -L "https://github.com/containernetworking/plugins/releases/download/${CNI_PLUGINS_VERSION}/cni-plugins-linux-${ARCH}-${CNI_PLUGINS_VERSION}.tgz" | sudo tar -C "$DEST" -xz

DOWNLOAD_DIR="/usr/local/bin"
sudo mkdir -p "$DOWNLOAD_DIR"

CRICTL_VERSION="v1.25.0"
ARCH="amd64"
curl -L "https://github.com/kubernetes-sigs/cri-tools/releases/download/${CRICTL_VERSION}/crictl-${CRICTL_VERSION}-linux-${ARCH}.tar.gz" | sudo tar -C $DOWNLOAD_DIR -xz

RELEASE="$(curl -sSL https://dl.k8s.io/release/stable.txt)"
ARCH="amd64"
cd $DOWNLOAD_DIR
sudo curl -L --remote-name-all https://dl.k8s.io/release/${RELEASE}/bin/linux/${ARCH}/{kubeadm,kubelet}
sudo chmod +x {kubeadm,kubelet}

RELEASE_VERSION="v0.4.0"
curl -sSL "https://raw.githubusercontent.com/kubernetes/release/${RELEASE_VERSION}/cmd/kubepkg/templates/latest/deb/kubelet/lib/systemd/system/kubelet.service" | sed "s:/usr/bin:${DOWNLOAD_DIR}:g" | sudo tee /etc/systemd/system/kubelet.service
sudo mkdir -p /etc/systemd/system/kubelet.service.d
curl -sSL "https://raw.githubusercontent.com/kubernetes/release/${RELEASE_VERSION}/cmd/kubepkg/templates/latest/deb/kubeadm/10-kubeadm.conf" | sed "s:/usr/bin:${DOWNLOAD_DIR}:g" | sudo tee /etc/systemd/system/kubelet.service.d/10-kubeadm.conf

systemctl enable --now kubelet

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

Configuring a cgroup driver

Both the container runtime and the kubelet have a property called "cgroup driver", which is important for the management of cgroups on Linux machines.

Troubleshooting

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

What's next

• Using kubeadm to Create a Cluster