Lubomir I. Ivanov
26f6a21308
The default kubelet configuration ConfigMap that kubeadm manages is "kubelet-config" instead of "kubelet-config-x.yy" (where x.yy is the Kubernetes version) in 1.24. Cleanup references to the legacy naming in kubeadm documentation. Generated contents in content/en/docs/reference/* are not updated.
124 lines
4.3 KiB
Markdown
124 lines
4.3 KiB
Markdown
---
|
|
title: Configuring a cgroup driver
|
|
content_type: task
|
|
weight: 10
|
|
---
|
|
|
|
<!-- overview -->
|
|
|
|
This page explains how to configure the kubelet cgroup driver to match the container
|
|
runtime cgroup driver for kubeadm clusters.
|
|
|
|
## {{% heading "prerequisites" %}}
|
|
|
|
You should be familiar with the Kubernetes
|
|
[container runtime requirements](/docs/setup/production-environment/container-runtimes).
|
|
|
|
<!-- steps -->
|
|
|
|
## Configuring the container runtime cgroup driver
|
|
|
|
The [Container runtimes](/docs/setup/production-environment/container-runtimes) 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.
|
|
|
|
## Configuring the kubelet cgroup driver
|
|
|
|
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.
|
|
|
|
{{< note >}}
|
|
|
|
In v1.22, if the user is not setting the `cgroupDriver` field under `KubeletConfiguration`,
|
|
`kubeadm` will default it to `systemd`.
|
|
{{< /note >}}
|
|
|
|
A minimal example of configuring the field explicitly:
|
|
|
|
```yaml
|
|
# kubeadm-config.yaml
|
|
kind: ClusterConfiguration
|
|
apiVersion: kubeadm.k8s.io/v1beta3
|
|
kubernetesVersion: v1.21.0
|
|
---
|
|
kind: KubeletConfiguration
|
|
apiVersion: kubelet.config.k8s.io/v1beta1
|
|
cgroupDriver: systemd
|
|
```
|
|
|
|
Such a configuration file can then be passed to the kubeadm command:
|
|
|
|
```shell
|
|
kubeadm init --config kubeadm-config.yaml
|
|
```
|
|
|
|
{{< note >}}
|
|
Kubeadm uses the same `KubeletConfiguration` for all nodes in the cluster.
|
|
The `KubeletConfiguration` is stored in a [ConfigMap](/docs/concepts/configuration/configmap)
|
|
object under the `kube-system` namespace.
|
|
|
|
Executing the sub commands `init`, `join` and `upgrade` would result in kubeadm
|
|
writing the `KubeletConfiguration` as a file under `/var/lib/kubelet/config.yaml`
|
|
and passing it to the local node kubelet.
|
|
{{< /note >}}
|
|
|
|
## Using the `cgroupfs` driver
|
|
|
|
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.
|
|
|
|
If you wish to configure a container runtime to use the `cgroupfs` driver,
|
|
you must refer to the documentation of the container runtime of your choice.
|
|
|
|
## Migrating to the `systemd` driver
|
|
|
|
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.
|
|
|
|
{{< note >}}
|
|
Alternatively, it is possible to replace the old nodes in the cluster with new ones
|
|
that use the `systemd` driver. This requires executing only the first step below
|
|
before joining the new nodes and ensuring the workloads can safely move to the new
|
|
nodes before deleting the old nodes.
|
|
{{< /note >}}
|
|
|
|
### Modify the kubelet ConfigMap
|
|
|
|
- Call `kubectl edit cm kubelet-config -n kube-system`.
|
|
- Either modify the existing `cgroupDriver` value or add a new field that looks like this:
|
|
|
|
```yaml
|
|
cgroupDriver: systemd
|
|
```
|
|
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:
|
|
|
|
- [Drain the node](/docs/tasks/administer-cluster/safely-drain-node) using `kubectl drain <node-name> --ignore-daemonsets`
|
|
- Stop the kubelet using `systemctl stop kubelet`
|
|
- 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 `systemctl start kubelet`
|
|
- [Uncordon the node](/docs/tasks/administer-cluster/safely-drain-node) using `kubectl uncordon <node-name>`
|
|
|
|
Execute these steps on nodes one at a time to ensure workloads
|
|
have sufficient time to schedule on different nodes.
|
|
|
|
Once the process is complete ensure that all nodes and workloads are healthy.
|