Managing Server Roles
Starting the K3s server with --cluster-init will run all control-plane components, including the apiserver, controller-manager, scheduler, and etcd. It is possible to disable specific components in order to split the control-plane and etcd roles on to separate nodes.
This document is only relevant when using embedded etcd. When not using embedded etcd, all servers will have the control-plane role and run control-plane components.
Dedicated etcd Nodes
To create a server with only the etcd role, start K3s with all the control-plane components disabled:
curl -fL https://get.k3s.io | sh -s - server --cluster-init --disable-apiserver --disable-controller-manager --disable-scheduler
This first node will start etcd, and wait for additional etcd and/or control-plane nodes to join. The cluster will not be usable until you join an additional server with the control-plane components enabled.
Dedicated control-plane Nodes
A dedicated control-plane node cannot be the first server in the cluster; there must be an existing node with the etcd role before joining dedicated control-plane nodes.
To create a server with only the control-plane role, start k3s with etcd disabled:
curl -fL https://get.k3s.io | sh -s - server --token <token> --disable-etcd --server https://<etcd-only-node>:6443
After creating dedicated server nodes, the selected roles will be visible in kubectl get node:
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
k3s-server-1 Ready etcd 5h39m v1.20.4+k3s1
k3s-server-2 Ready control-plane,master 5h39m v1.20.4+k3s1
Adding Roles To Existing Servers
Roles can be added to existing dedicated nodes by restarting K3s with the disable flags removed. For example ,if you want to add the control-plane role to a dedicated etcd node, you can remove the --disable-apiserver --disable-controller-manager --disable-scheduler flags from the systemd unit or config file, and restart the service.
Configuration File Syntax
As with all other CLI flags, you can use the Configuration File to disable components, instead of passing the options as CLI flags. For example, to create a dedicated etcd node, you can place the following values in /etc/rancher/k3s/config.yaml:
cluster-init: true
disable-apiserver: true
disable-controller-manager: true
disable-scheduler: true