In the cloud-native world, Kubernetes remains the de facto standard in container orchestration. Even so, it is strong, but its power and resource needs can easily be overkill in lightweight environments, edge computing, and IoT devices. And here comes K3s, a lightweight and fully functional Kubernetes distribution specifically tailored for resource-constrained environments.
This in-depth blog post will explore K3s, its architecture, and key use cases.
What is K3s?
A distribution developed by Rancher Labs with lightweight Kubernetes, popularly known as K3s, brings Kubernetes to the edge and IoT environments without sacrificing essential functionality.
Fun Fact: You can stand up your K3s cluster in under 90 seconds.
Official documentation describes the mystery behind the name. K3s was an installation of Kubernetes but half the size regarding memory footprint. Kubernetes is stylized as k8s, a 10-letter word. To emphasize the nearly half reduction in the size of Rancher Labs' new flavour, the name came out to be a 5-letter word stylized as K3s. There isn't a long form of K3s or any official pronunciation.
Key Features of K3s:
- Small Footprint: K3s is built as a single binary under 40MB that effectively implements the Kubernetes API. Its very minimal resource usage allows the running of a cluster on machines with as little as 512MB of RAM. These properties usually mean clusters can be deployed in under two minutes with only a few nodes.
- Simplified Architecture: It has removed legacy, non-essential components, such as in-tree cloud providers, and alpha features, yet remains full-featured Kubernetes.
- Optimized for Resource Constraints: K3s perform well even on as little as 512MB of RAM and can be deployed on low-powered devices.
- Integrated SQLite Database: B K3s performs well even on as little as 512MB of RAM and can be deployed on low-powered devices.
- Built-In Support for Containers: The runtime container is contained, used by default to save on overhead and makes the runtime faster.
- Simplified Security: K3s offers native Helm controllers, local storage providers, and the simplicity of TLS certificates; so it introduces simplification of edge devices at a security level.
K3s Architecture
Just because K3s has recorded its smallest size does not necessarily mean its architectural structure is foreign in terms of its light nature as compared to Kubernetes.
Key Components:
- K3s Server: It is one cluster controller that is related to Kubernetes as well and will control the etcd DB, and API server, together with the scheduler and also the controllers.
- K3s Agent: Runs on every node and is used for workload management, communicates with the control plane, and also runs containerd.
- Containerd: The default runtime for containers, containerd manages to pull, store, and execute the containers.
- Traefik: An Optional ingress controller used within K3s and enables HTTP routing and load balancing.
- Flannel: By default, K3s uses Flannel for the CNI (Container Network Interface) and supports the flow of network traffic among nodes in a cluster.
- Security: K3s has security as its first design consideration. This means it uses the fewest permissions possible and relies on defaults that help eliminate vulnerability and make it much easier to manage certificates. The server automatically generates self-signed certificates to make it even easier to manage TLS.
Common Use Cases for K3s
Photo by Jorge Ramirez on UnsplashK3s are designed with specific environments and use cases in mind, particularly where traditional Kubernetes may be too resource-heavy. Below are some common scenarios where K3s excels:
1. Edge Computing
Edge devices, such as IoT gateways, are resource-constrained but benefit from running containerized applications. K3s can bring Kubernetes orchestration to the edge, allowing you to manage distributed applications at scale.
2. IoT Devices
Multiple IoT devices can go into management to install K3s on a Raspberry Pi then to then deploy and manage microservices across hundreds or thousands of devices.
CI/CD in Low-Resource Environments
3. CI/CD in Low-Resource Environments
In environments with scarce compute resources, be it smaller CI/CD pipelines or isolated environments, K3s can provide the whole Kubernetes experience without needing the heavy resources the full version of Kubernetes would.
4. Dev and Test Environments
For Dev, Test, or Stage Environments, usage for the developer to test things that wouldn't break in one of these will do best without the overhead of the hassle that comes from trying to set up a whole standard cluster with Kubernetes.
5. Air-Gapped or Offline Deployments
Since K3s has minimal external dependencies, it is very fit for an air-gapped or offline environment where one would likely have limited possibilities to gain access to the external internet, or might not even have it at all.
K3s vs. K8s
The answer to K3s vs. K8s is that this, in fact, is not entirely a valid comparison because K3s is a Kubernetes distribution. The real difference between K3s and K8s is that K3s was designed to have a smaller memory footprint and special characteristics that fit certain environments like edge computing or IoT.
So, it is not about what the differences are between K3s and K8s but when and for which environment you should choose one over the other. Everything depends on the specific needs and resources of the project, and therefore the decision to use K8s or K3s as well.
For instance, if you are spinning Kubernetes clusters up and down frequently for cloud bursting, running batch jobs, or continuous integration testing, you will appreciate how quickly a K3s cluster comes online.
Best Practices for Running K3s in Production
Even though K3s is built for lightweight, edge, and resource-constrained environments, it can also be used in production. Here are some best practices:
- Use an External Database: SQLite is acceptable for small clusters, whereas an external database like MySQL, PostgreSQL, etcd must be used in the production environment to achieve much better performance and scalability.
- Backup Configuration and State: Back up the state of the cluster and the configuration to prevent data from getting lost in case some changes are made.
- Harden Security: While the defaults by K3s are reasonable, securing the API server, control plane, and node-to-node communication remains necessary for a multi-node cluster.
- Monitor Resource Usage: Even though K3s is lightweight, monitoring resource consumption on edge devices is critical to avoid bottlenecks.
Conclusion
K3s tries to fill the gap between powerful Kubernetes orchestration and environments with scarce resources such as edge computing, IoT, and lightweight devices through having a small footprint, easy installation, and simple management.
Whether you're on devices with IoT are supporting edge workloads or have just needed a super light development cluster, K3s brings power within access in ways it couldn't be accessed. Should your need be Kubernetes on diet, then the perfect remedy is none.