fgiudici / elemental

Elemental is an immutable Linux distribution built to run Rancher and it's corresponding Kubernetes distributions RKE2 and k3s. It is built using the Elemental-toolkit

Architecture

RancherOS v2 is an immutable Linux distribution built to run Rancher and it's corresponding Kubernetes distributions RKE2 and k3s. It is built using the cOS-toolkit and based on openSUSE. Initial node configurations is done using a cloud-init style approach and all further maintenance is done using Kubernetes operators.

Use Cases

RancherOS is intended to be ran as the operating system beneath a Rancher Multi-Cluster Management server or as a node in a Kubernetes cluster managed by Rancher. RancherOS also allows you to build stand alone Kubernetes clusters that run an embedded and smaller version of Rancher to manage the local cluster. A key attribute of RancherOS is that it is managed by Rancher and thus Rancher will exist either locally in the cluster or centrally with Rancher Multi-Cluster Manager.

OCI Image based

RancherOS v2 is an image based distribution with an A/B style update mechanism. One first runs on a read-only image A and to do an upgrade pulls a new read only image B and then reboots the system to run on B. What is unique about RancherOS v2 is that the runtime images come from OCI Images. Not an OCI Image containing special artifacts, but an actual Docker runnable image that is built using standard Docker build processes. RancherOS is built using normal docker build and if you wish to customize the OS image all you need to do is create a new Dockerfile.

rancherd

RancherOS v2 includes no container runtime, Kubernetes distribution, or Rancher itself. All of these assests are dynamically pulled at runtime. All that is included in RancherOS is rancherd which is responsible for bootstrapping RKE2/k3s and Rancher from an OCI registry. This means an update to containerd, k3s, RKE2, or Rancher does not require an OS upgrade or node reboot.

cloud-init

RancherOS v2 is initially configured using a simple version of cloud-init. It is not expected that one will need to do a lot of customization to RancherOS as the core OS's sole purpose is to run Rancher and Kubernetes and not serve as a generic Linux distribution.

RancherOS Operator

RancherOS v2 includes an operator that is responsible for managing OS upgrades and managing a secure device inventory to assist with zero touch provisioning.

openSUSE Leap

RancherOS v2 is based off of openSUSE Leap. There is no specific dependency on openSUSE beyond that RancherOS assumes the underlying distribution is based on systemd. We choose openSUSE for obvious reasons, but beyond that openSUSE Leap provides a stable layer to build upon that is well tested and has paths to commercial support, if one chooses.