Kubeadm unknown service runtime.v1alpha2.RuntimeService

Problem
Following Kubernetes official installation instruction for containerd and kubeadm init will fail with unknown service runtime.v1alpha2.RuntimeService.

# Commands from https://kubernetes.io/docs/setup/production-environment/container-runtimes/#containerd
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 [arch=amd64] https://download.docker.com/linux/ubuntu focal stable"
apt-get update && apt-get install -y containerd.io

# Configure containerd
mkdir -p /etc/containerd
containerd config default > /etc/containerd/config.toml
systemctl restart containerd

kubeadm init
...
[preflight] Running pre-flight checks
error execution phase preflight: [preflight] Some fatal errors occurred:
	[ERROR CRI]: container runtime is not running: output: time="2020-09-24T11:49:16Z" level=fatal msg="getting status of runtime failed: rpc error: code = Unimplemented desc = unknown service runtime.v1alpha2.RuntimeService"
, error: exit status 1

Solution:

rm /etc/containerd/config.toml
systemctl restart containerd
kubeadm init