Lightweight Kubernetes. Production ready, easy to install, half the memory, all in a binary less than 100 MB.
Great for:
K3s is a fully conformant production-ready Kubernetes distribution with the following changes:
K3s bundles the following technologies together into a single cohesive distribution:
These technologies can be disabled or swapped out for technologies of your choice.
Additionally, K3s simplifies Kubernetes operations by maintaining functionality for:
We wanted an installation of Kubernetes that was half the size in terms of memory footprint. Kubernetes is a 10 letter word stylized as k8s. So something half as big as Kubernetes would be a 5 letter word stylized as K3s. There is neither a long-form of K3s nor official pronunciation.
No, it's a distribution. A fork implies continued divergence from the original. This is not K3s's goal or practice. K3s explicitly intends not to change any core Kubernetes functionality. We seek to remain as close to upstream Kubernetes as possible. However, we maintain a small set of patches (well under 1000 lines) important to K3s's use case and deployment model. We maintain patches for other components as well. When possible, we contribute these changes back to the upstream projects, for example, with SELinux support in containerd. This is a common practice amongst software distributions.
K3s is a distribution because it packages additional components and services necessary for a fully functional cluster that go beyond vanilla Kubernetes. These are opinionated choices on technologies for components like ingress, storage class, network policy, service load balancer, and even container runtime. These choices and technologies are touched on in more detail in the What is this? section.
There are two major ways that K3s is lighter weight than upstream Kubernetes:
The memory footprint is reduced primarily by running many components inside of a single process. This eliminates significant overhead that would otherwise be duplicated for each component.
The binary is smaller by removing third-party storage drivers and cloud providers, explained in more detail below.
This is a common point of confusion because it has changed over time. Early versions of K3s had much more removed than the current version. K3s currently removes two things:
Both of these have out-of-tree alternatives in the form of CSI and CCM, which work in K3s and which upstream is moving towards.
We remove these to achieve a smaller binary size. They can be removed while remaining conformant because neither affects core Kubernetes functionality. They are also dependent on third-party cloud or data center technologies/services, which may not be available in many K3s' use cases.
Check out our roadmap to see what we have planned moving forward.
K3s maintains pace with upstream Kubernetes releases. Our goal is to release patch releases within one week, and new minors within 30 days.
Our release versioning reflects the version of upstream Kubernetes that is being released. For example, the K3s release v1.27.4+k3s1 maps to the v1.27.4
Kubernetes release. We add a postfix in the form of +k3s<number>
to allow us to make additional releases using the same version of upstream Kubernetes while remaining semver compliant. For example, if we discovered a high severity bug in v1.27.4+k3s1
and needed to release an immediate fix for it, we would release v1.27.4+k3s2
.
Please see the official docs site for complete documentation.
The install.sh
script provides a convenient way to download K3s and add a service to systemd or openrc.
To install k3s as a service, run:
curl -sfL https://get.k3s.io | sh -
A kubeconfig file is written to /etc/rancher/k3s/k3s.yaml
and the service is automatically started or restarted.
The install script will install K3s and additional utilities, such as kubectl
, crictl
, k3s-killall.sh
, and k3s-uninstall.sh
, for example:
sudo kubectl get nodes
K3S_TOKEN
is created at /var/lib/rancher/k3s/server/node-token
on your server.
To install on worker nodes, pass K3S_URL
along with
K3S_TOKEN
environment variables, for example:
curl -sfL https://get.k3s.io | K3S_URL=https://myserver:6443 K3S_TOKEN=XXX sh -
k3s
from latest release, x86_64, armhf, arm64 and s390x are supported.sudo k3s server &
# Kubeconfig is written to /etc/rancher/k3s/k3s.yaml
sudo k3s kubectl get nodes
# On a different node run the below. NODE_TOKEN comes from
# /var/lib/rancher/k3s/server/node-token on your server
sudo k3s agent --server https://myserver:6443 --token ${NODE_TOKEN}
Please check out our contributing guide if you're interested in contributing to K3s.
Security issues in K3s can be reported by sending an email to security@k3s.io. Please do not file issues about security issues.
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