k3s

k3s is a lightweight Kubernetes distribution “for IoT and Edge Computing”:

Installation

dnf install -y container-selinux selinux-policy-base
rpm -i https://rpm.rancher.io/k3s-selinux-0.1.1-rc1.el7.noarch.rpm

curl -sfL https://get.k3s.io | sh -
# wait....
k3s kubectl get node

You’ll need to be root to interact with the cluster:

sudo k3s kubectl get node

Concepts

DNS:

• Uses coredns using image docker.io/rancher/coredns-coredns
• This runs as a ReplicaSet in namespace kube-system
• CoreDNS gets settings from the configmap coredns in namespace kube-system - this is mounted as /etc/coredns/Corefile in the container
• Each container uses CoreDNS for DNS resolution, due to nameserver <kube-dns Service IP> in /etc/resolv.conf

Cookbook

Kill, uninstall:

/usr/local/bin/k3s-killall.sh
/usr/local/bin/k3s-uninstall.sh

Adding the Kubernetes Dashboard:

GITHUB_URL=https://github.com/kubernetes/dashboard/releases
VERSION_KUBE_DASHBOARD=$(curl -w '%{url_effective}' -I -L -s -S ${GITHUB_URL}/latest -o /dev/null | sed -e 's|.*/||')
sudo k3s kubectl create -f https://raw.githubusercontent.com/kubernetes/dashboard/${VERSION_KUBE_DASHBOARD}/aio/deploy/recommended.yaml

Some more info about k3s:

• It’ll create a service to run on startup: /etc/systemd/system/multi-user.target.wants/k3s.service
• Use the k3s command to interact with the cluster.
• It runs as root.
• It is configured to automatically restart after node reboots or if the process crashes or is killed
• There is a config file in /etc/rancher/k3s/k3s.yaml
• You can use the scripts /usr/local/bin/k3s-killall.sh and k3s-uninstall.sh to stop and uninstall, etc.