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Personal notes for setting up a Kubernetes cluster on bare metal.

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kubernetes-bare-metal

Kubernetes setup for Ubuntu on bare metal.

The intent is to outline the steps necessary to install a multi-node Kubernetes 1.18 cluster on Ubuntu 18.04.

Components

  • Ubuntu 18.04
  • Kubernetes 1.18 with cgroups-driver=systemd
  • Docker 19.03.11
  • Docker Hub Registry
  • Weave 2.6.2
  • Web UI (kubernetes dashboard)

Gotchas

  • Versions
  • Ensuring cgroups-driver for Docker and Kubelet match
  • Starting over:
    • kubeadm reset
    • sudo rm -rf /etc/kubernetes
  • Making changes to kubelet:
    • systemctl daemon-reload
    • systemctl restart kubelet

Docker

Installation

First, update existing list of packages:

sudo apt update

Next, install prerequisites:

sudo apt install apt-transport-https ca-certificates curl software-properties-common

Add the GPG key for the official Docker repository:

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -`

Add the Docker repository to APT sources:

sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable"

Update package database with the Docker packages:

sudo apt update

Make sure you are about to install from the Docker repo instead of the default Ubuntu repo:

apt-cache policy docker-ce

Now, install:

sudo apt install docker-ce

Confirm install:

sudo systemctl status docker

should return somethink like:

docker.service - Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2020-06-19 15:27:09 UTC; 4s ago
     Docs: https://docs.docker.com
 Main PID: 17823 (dockerd)
    Tasks: 22
   CGroup: /system.slice/docker.service
           └─17823 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

docker version

Client: Docker Engine - Community
 Version:           19.03.11
 API version:       1.40
 Go version:        go1.13.10
 Git commit:        42e35e61f3
 Built:             Mon Jun  1 09:12:22 2020
 OS/Arch:           linux/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          19.03.11
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.13.10
  Git commit:       42e35e61f3
  Built:            Mon Jun  1 09:10:54 2020
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.2.13
  GitCommit:        7ad184331fa3e55e52b890ea95e65ba581ae3429
 runc:
  Version:          1.0.0-rc10
  GitCommit:        dc9208a3303feef5b3839f4323d9beb36df0a9dd
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683

Post-install Configuration

Update cgroupdriver in /etc/docker/daemon.json to use systemd:

{
  "exec-opts": [
    "native.cgroupdriver=systemd"
  ],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  },
  "storage-driver": "overlay2"
}

Restart Docker daemon via:

systemctl restart docker

Verify Docker cgroup driver via:

docker info -f {{.CgroupDriver}}

kubectl, kubeadm, kubelet

sudo apt-get update && sudo apt-get install -y apt-transport-https curl
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF
sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl

kubectl version -o json

{
  "clientVersion": {
    "major": "1",
    "minor": "18",
    "gitVersion": "v1.18.0",
    "gitCommit": "9e991415386e4cf155a24b1da15becaa390438d8",
    "gitTreeState": "clean",
    "buildDate": "2020-03-25T14:58:59Z",
    "goVersion": "go1.13.8",
    "compiler": "gc",
    "platform": "linux/amd64"
  },
  "serverVersion": {
    "major": "1",
    "minor": "18",
    "gitVersion": "v1.18.0",
    "gitCommit": "9e991415386e4cf155a24b1da15becaa390438d8",
    "gitTreeState": "clean",
    "buildDate": "2020-03-25T14:50:46Z",
    "goVersion": "go1.13.8",
    "compiler": "gc",
    "platform": "linux/amd64"
  }
}

Add gpg key:

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -

Configuration

Disable Swap

sudo swapoff -a

To permanently disable swap (to survive reboot) then remove any swap entry from /etc/fstab.

Configure kubeadm and kubelet

sudo apt update
sudo apt install -y apt-transport-https ca-certificates curl software-properties-common gnupg2

Create dir if it doesn't exist:

sudo mkdir -p /var/lib/kubelet

Add the following to /var/lib/kubelet/kubeadm-flags.env:

KUBELET_KUBEADM_ARGS="--cgroup-driver=systemd --network-plugin=cni --pod-infra-container-image=k8s.gcr.io/pause:3.2 --resolv-conf=/run/systemd/resolve/resolv.conf"

Install the cluster via: sudo kubeadm init -v=6

Troubleshooting kubelet

The following are your friends when troubleshooting kubelet startup issues:

Get the status of the kubelet service: systemctl status kubelet

Look at the logs of the kubelet service (scroll to bottom): journalctl -xeu kubelet

Post Install

sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Weave

Install via:

kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"

To disable NPC:

kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')&disable-npc=true"

Join Additional Nodes (workers)

After running kubeadm init on the master node, there will be output including something like the below snipper:

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 192.168.7.40:6443 --token th6npu.fmuxapxjzsx8k7zt \
    --discovery-token-ca-cert-hash sha256:e947ea9db4ef3182ac870618d300c16cac09d6de45c28ffab73b74099f673870

If you need to add nodes later on and need the join command, use the following command to print it from the master node:

kubeadm token create --print-join-command

Dashboard

Create user

Taken from: https://github.com/kubernetes/dashboard/blob/master/docs/user/access-control/creating-sample-user.md

Create a file called dashboard-adminuser.yaml with the following content:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: admin-user
  namespace: kubernetes-dashboard  
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: admin-user
roleRef:  
  kind: ClusterRole
  name: cluster-admin
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: ServiceAccount
  name: admin-user
  namespace: kubernetes-dashboard
- kind: ServiceAccount
  name: admin-user
  namespace: default

Use the following to apply/create:

kubectl apply -f dashboard-adminuser.yaml

Install Dashboard

kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.0.0-rc6/aio/deploy/recommended.yaml

Start Dashboard Proxy

kubectl proxy

Login

First, get the bearer token via:

kubectl -n kubernetes-dashboard describe secret $(kubectl -n kubernetes-dashboard get secret | grep admin-user | awk '{print $1}')

Second, visit http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/ and login with the bearer token.

Pulling from Private Docker Registries

In order to all Kubernetes to pull from private Docker registries you need to create a secret with the registry credentials then add the secret to the default service account.

kubectl create secret docker-registry dockerhubregistrykey --docker-server=https://index.docker.io/v1/ --docker-username=digitalsanctum --docker-password=YOUR_PASSWORD --docker-email=shane@digitalsanctum.com
kubectl edit serviceaccounts default

Add the following to the file after secrets:

imagePullSecrets:
- name: dockerhubregistrykey

Save the file as sa.yaml then update the service account via:

kubectl replace serviceaccount default -f ./sa.yaml

Finally, update deployment.yaml with imagePullSecrets:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: kgen
  namespace: default
  labels:
    app: kgen
spec:
  replicas: 1
  selector:
    matchLabels:
      app: kgen
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 25%
      maxSurge: 25%
  revisionHistoryLimit: 10
  progressDeadlineSeconds: 600
  template:
    metadata:
      labels:
        app: kgen
        cluster-name: kubernetes
    spec:
      serviceAccountName: kgen-sa
      imagePullSecrets:
        - name: dockerhubregistrykey
      containers:
        - name: kgen
          image: digitalsanctum/kgen-service:0.1.0
          imagePullPolicy: IfNotPresent
          ports:
            - name: http
              containerPort: 8080
              protocol: TCP
          env:
            - name: SPRING_PROFILES_ACTIVE
              value: local
            - name: POD_NAME
              value: metadata.name
          readinessProbe:
            httpGet:
              path: /actuator/health
              port: 8080
            initialDelaySeconds: 5
            periodSeconds: 60
            timeoutSeconds: 2
            failureThreshold: 1
            successThreshold: 1
          livenessProbe:
            httpGet:
              path: /actuator/health
              port: 8080
            initialDelaySeconds: 15
            periodSeconds: 70
            timeoutSeconds: 5
            failureThreshold: 2
            successThreshold: 1
          resources:
            limits:
              cpu: 500m
              memory: 1Gi
            requests:
              cpu: 250m
              memory: 500Mi

Updating a deployment

First, grab the deployment via:

kubectl get deployments kgen-service -o yaml > kgen-service-deployment.yaml

Second, edit the file as necessary.

Lastly, update the deployment with your changes:

kubectl replace deployments kgen-service -f ./kgen-service-deployment.yaml

-OR-

Just edit the deployment. When it's saved the deployment will be replaced:

kubectl edit deployments kgen-service

Get a list of all containers running in all pods in all namespaces

kubectl get pods --all-namespaces -o jsonpath={..image} | tr -s '[[:space:]]' '\n' | sort -u

Port forwarding

Forward one or more local ports to a pod. This command requires the node to have 'socat' installed.

As an example to port forward to an application listening on port 8080:

kubectl port-forward deployment/kgen-service 8080

Multiple Clusters

To view the available contexts/clusters:

kubectl config get-contexts

To switch from one cluster to another:

kubectl config use-context kubernetes-admin@kubernetes

Custom Namespaces

kubectl get pods -n <custom-namespace>

Scaling your deployments

kubectl scale deployment <app-name> --replicas <replica-count>

Zero downtime deployments

The default way to update a running application in Kubernetes is to deploy a new image tag to your Docker registry and then deploy it using:

kubectl set image deployment/<app-name>-app <app-name>=<new-image>

Using livenessProbes and readinessProbe allows you to tell Kubernetes about the state of your applications, in order to ensure availability of your services. You will need a minimum of 2 replicas for every application if you want to have zero downtime deployment. This is because the rolling upgrade strategy first stops a running replica in order to place a new one. Running only one replica will cause a short downtime during upgrades.

Troubleshooting

Deploy Verification

Wait for deploy to complete:

kubectl rollout status -n default deployments/springboot-microservice --watch

-or-

`curl --silent --fail --retry 60 --retry-delay 5 --retry-connrefused --insecure --output /dev/null $ENDPOINT/health`

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Personal notes for setting up a Kubernetes cluster on bare metal.

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kubernetes k8s k8s-cluster kubernetes-install k8s-cluster-ubuntu

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