Configuring a cgroup driver

    You should be familiar with the Kubernetes container runtime requirements.

    The page explains that the systemd driver is recommended for kubeadm based setups instead of the cgroupfs driver, because kubeadm manages the kubelet as a systemd service.

    The page also provides details on how to setup a number of different container runtimes with the systemd driver by default.

    kubeadm allows you to pass a KubeletConfiguration structure during kubeadm init. This KubeletConfiguration can include the cgroupDriver field which controls the cgroup driver of the kubelet.

    Such a configuration file can then be passed to the kubeadm command:

    As this guide explains using the cgroupfs driver with kubeadm is not recommended.

    To continue using cgroupfs and to prevent kubeadm upgrade from modifying the KubeletConfiguration cgroup driver on existing setups, you must be explicit about its value. This applies to a case where you do not wish future versions of kubeadm to apply the systemd driver by default.

    See the below section on “Modify the kubelet ConfigMap” for details on how to be explicit about the value.

    To change the cgroup driver of an existing kubeadm cluster to systemd in-place, a similar procedure to a kubelet upgrade is required. This must include both steps outlined below.

    • Find the kubelet ConfigMap name using kubectl get cm -n kube-system | grep kubelet-config.

    • Call kubectl edit cm kubelet-config-x.yy -n kube-system (replace x.yy with the Kubernetes version).

    • Either modify the existing cgroupDriver value or add a new field that looks like this:

      This field must be present under the kubelet: section of the ConfigMap.

    Update the cgroup driver on all nodes

    For each node in the cluster:

    • using kubectl drain <node-name> --ignore-daemonsets
    • Stop the container runtime
    • Modify the container runtime cgroup driver to systemd
    • Set cgroupDriver: systemd in /var/lib/kubelet/config.yaml
    • Start the container runtime
    • Start the kubelet using

    Once the process is complete ensure that all nodes and workloads are healthy.