Master-1
curl -sfL https://get.k3s.io | K3S_KUBECONFIG_MODE="644" INSTALL_K3S_EXEC="--cluster-init" sh -
Get the token from /var/lib/rancher/k3s/server/node-token
Master-n
curl -sfL https://get.k3s.io | K3S_KUBECONFIG_MODE="644" INSTALL_K3S_EXEC="server --server https://<IP>:6443 --token <TOKEN>" sh -
client-n
curl -sfL https://get.k3s.io | K3S_URL=https://<IP>:6443 K3S_TOKEN=<TOKEN> sh -