Container Runtimes
You need to install a container runtime into each node in the cluster so that Pods can run there. This page outlines what is involved and describes related tasks for setting up nodes.
Kubernetes 1.34 requires that you use a runtime that conforms with the Container Runtime Interface (CRI).
See CRI version support for more information.
This page provides an outline of how to use several common container runtimes with Kubernetes.
Note:
Kubernetes releases before v1.24 included a direct integration with Docker Engine, using a component named dockershim. That special direct integration is no longer part of Kubernetes (this removal was announced as part of the v1.20 release). You can read Check whether Dockershim removal affects you to understand how this removal might affect you. To learn about migrating from using dockershim, see Migrating from dockershim.
If you are running a version of Kubernetes other than v1.34, check the documentation for that version.
Install and configure prerequisites
Network configuration
By default, the Linux kernel does not allow IPv4 packets to be routed between interfaces. Most Kubernetes cluster networking implementations will change this setting (if needed), but some might expect the administrator to do it for them. (Some might also expect other sysctl parameters to be set, kernel modules to be loaded, etc; consult the documentation for your specific network implementation.)
Enable IPv4 packet forwarding
To manually enable IPv4 packet forwarding:
# sysctl params required by setup, params persist across reboots
cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.ipv4.ip_forward = 1
EOF
# Apply sysctl params without reboot
sudo sysctl --system
Verify that net.ipv4.ip_forward is set to 1 with:
sysctl net.ipv4.ip_forward
cgroup drivers
On Linux, control groups are used to constrain resources that are allocated to processes.
Both the kubelet and the underlying container runtime need to interface with control groups to enforce resource management for pods and containers and set resources such as cpu/memory requests and limits. To interface with control groups, the kubelet and the container runtime need to use a cgroup driver. It's critical that the kubelet and the container runtime use the same cgroup driver and are configured the same.
There are two cgroup drivers available: