K8s
Alpine Linux K8s in 10 Minutes
Summary
This guide will allow you to deploy a fresh Alpine Linux install into a Kubernetes K8 cluster in less than 10 minutes.
Why
I went to learn Kubernetes recently and I built a k3 cluster using Alpine in an hour or so, it was a great experience. I figured the next step would be K8s, but I found no material on K8s for Alpine. This guide is the result of my first pass and the incorporations of high quality notes from the contributers. Kubernetes is awesome.
Contributers
Build K8s on Alpine Linux
Prerequisits
You need an Alpine Linux install (this guide is written against version 3.15 standard image) with internet access. I recommend at least 2 CPU with 4GB of ram and 10GB of disk for each node.
For HA control planes you'll need a mininum of three nodes
1. Setup the Repositories
Update you repositories under /etc/apk/repositories to include community, edge community and testing.
#/media/cdrom/apks http://dl-cdn.alpinelinux.org/alpine/v3.15/main http://dl-cdn.alpinelinux.org/alpine/v3.15/community #http://dl-cdn.alpinelinux.org/alpine/edge/main http://dl-cdn.alpinelinux.org/alpine/edge/community http://dl-cdn.alpinelinux.org/alpine/edge/testing
2. Node Setup
This series of commands solves a series is incremental problems and sets up the system (if the first control node) for kubectl/kubeadm to run properly on next login by linking the config.
The result here gives you a functional node that can be joined to an existing cluster or can become the first control plane of a new cluster. 🎶
*** This build assumes CNI usage of flannel for networking ***
#add kernel module for networking stuff echo "br_netfilter" > /etc/modules-load.d/k8s.conf modprobe br_netfilter apk add cni-plugin-flannel apk add cni-plugins apk add flannel apk add flannel-contrib-cni apk add kubelet apk add kubeadm apk add kubectl apk add docker apk add uuidgen apk add nfs-utils #Pin your versions! If you update and the nodes get out of sync, it implodes. apk add 'kubelet=~1.23' apk add 'kubeadm=~1.23' apk add 'kubectl=~1.23' #get rid of swap cat /etc/fstab | grep -v swap > temp.fstab cat temp.fstab > /etc/fstab rm temp.fstab swapoff -a #Fix prometheus errors mount --make-rshared / echo "#!/bin/sh" > /etc/local.d/sharemetrics.start echo "mount --make-rshared /" >> /etc/local.d/sharemetrics.start chmod +x /etc/local.d/sharemetrics.start rc-update add local #Fix id error messages uuidgen > /etc/machine-id #Add services rc-update add docker rc-update add kubelet #Sync time rc-update add ntpd /etc/init.d/ntpd start /etc/init.d/docker start #fix flannel ln -s /usr/libexec/cni/flannel-amd64 /usr/libexec/cni/flannel #kernel stuff echo "net.bridge.bridge-nf-call-iptables=1" >> /etc/sysctl.conf sysctl net.bridge.bridge-nf-call-iptables=1
Your blank node is now ready! If it's the first, you'll want to make a control node.
3. Setup the Control Plane (New Cluster!)
Run this command to start the cluster and then apply a network.
#do not change subnet kubeadm init --pod-network-cidr=10.244.0.0/16 --node-name=master mkdir ~/.kube ln -s /etc/kubernetes/admin.conf /root/.kube/config kubectl apply -f https://raw.githubusercontent.com/flannel-io/flannel/master/Documentation/kube-flannel.yml
You now have a control plane. This also gives you the command to run on our blank nodes to add them to this cluster as workers.
4. Join the cluster.
Run this to get the join command from the control plane which you would then run on your new worker.
kubeadm token create --print-join-command
Bonus
Setup NFS Mounts on K8s
This can be shared NFS storage to allow for auto persistent claim fulfilment. You'll need your IP updated and export information.
helm repo add nfs-subdir-external-provisioner https://kubernetes-sigs.github.io/nfs-subdir-external-provisioner/
helm install nfs-subdir-external-provisioner nfs-subdir-external-provisioner/nfs-subdir-external-provisioner \
--set nfs.server=192.168.1.31 \
--set nfs.path=/exports/cluster00
Now set the default storage class for the cluster.
kubectl get storageclass
kubectl patch storageclass nfs-client -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'
Check on System
Check on your system.
kubectl get nodes kubectl get all