Kubernetes The Hard Way

Updated Dec 29, 2023 ·

Some of the scenario questions here are based on Kodekloud's CKA course labs.

NOTE

CKAD and CKA can have similar scenario questions. It is recommended to go through the CKAD practice tests.

Shortcuts

First run the two commands below for shortcuts.

export do="--dry-run=client -o yaml" 
export now="--force --grace-period=0"

Questions

Install the kubeadm and kubelet packages on the controlplane and node01 nodes.

Use the exact version of 1.27.0-2.1 for both.

Answer

Complete steps can be found here: https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/install-kubeadm/

sudo apt-get update
# apt-transport-https may be a dummy package; if so, you can skip that package
sudo apt-get install -y apt-transport-https ca-certificates curl gpg

Check if OS is Ubuntu,if it is, then need to create the /etc/apt/keyrings.

controlplane ~ ➜  cat /etc/os-release 
NAME="Ubuntu"
VERSION="20.04.6 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.6 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal

controlplane ~ ➜  sudo mkdir -m 755 /etc/apt/keyrings 

Continue with the steps from the docs.

controlplane ~ ➜  curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.27/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg  

# This overwrites any existing configuration in /etc/apt/sources.list.d/kubernetes.list
echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.27/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list

sudo apt-get install -y \
kubelet=1.27.0-2.1 \
kubeadm=1.27.0-2.1 \
kubectl=1.27.0-2.1 

Verify.

controlplane ~ ➜  kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"27", GitVersion:"v1.27.0", GitCommit:"1b4df30b3cdfeaba6024e81e559a6cd09a089d65", GitTreeState:"clean", BuildDate:"2023-04-11T17:09:06Z", GoVersion:"go1.20.3", Compiler:"gc", Platform:"linux/amd64"}

controlplane ~ ➜  kubectl version
WARNING: This version information is deprecated and will be replaced with the output from kubectl version --short.  Use --output=yaml|json to get the full version.
Client Version: version.Info{Major:"1", Minor:"27", GitVersion:"v1.27.0", GitCommit:"1b4df30b3cdfeaba6024e81e559a6cd09a089d65", GitTreeState:"clean", BuildDate:"2023-04-11T17:10:18Z", GoVersion:"go1.20.3", Compiler:"gc", Platform:"linux/amd64"}
Kustomize Version: v5.0.1
Error from server (NotFound): the server could not find the requested resource

Repeat the same steps to setup node01.

After installing the required tools in the previous question, bootstrap the Kubernetes cluster using kubeadm. Initialize Control Plane Node (Master Node). Use the following options:
- apiserver-advertise-address - Use the IP address allocated to eth0 on the controlplane node
- apiserver-cert-extra-sans - Set it to controlplane
- pod-network-cidr - Set to 10.244.0.0/16
Once done, set up the default kubeconfig file and wait for node to be part of the cluster.
Answer
Complete steps can be found here: https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/
Get the controlplane's IP first.
controlplane ~ ✖ ip addr | grep eth0 5817: eth0@if5818: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UP group default inet 192.17.66.9/24 brd 192.17.66.255 scope global eth0
Then run kube init with the supplied values.
kubeadm init \ --apiserver-advertise-address 192.17.66.9 \ --apiserver-cert-extra-sans controlplane \ --pod-network-cidr 10.244.0.0/16
To make kubectl work for your non-root user, setup the default kubeconfig file. Run these commands, which are also part of the kubeadm init output:
mkdir -p $HOME/.kube sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config
Take note of the output:
Then you can join any number of worker nodes by running the following on each as root: kubeadm join 192.17.66.9:6443 --token n3131u.ndrbw41snadbex5r \ --discovery-token-ca-cert-hash sha256:0d557809cfe18f10cbba69fe455aa3b03dad336824cbba62a29fe81ee8a18d9f

After controlplane is bootstrapped, join the node01 to the cluster.

Answer

Run the kubeadm join command which was returned by the kubeadm output.

kubeadm join 192.17.66.9:6443 --token n3131u.ndrbw41snadbex5r \
        --discovery-token-ca-cert-hash sha256:0d557809cfe18f10cbba69fe455aa3b03dad336824cbba62a29fe81ee8a18d9f

Once it's done running, return to the controlplane and verify if it can see the node01 in the cluster.

controlplane ~ ➜  k get no
NAME           STATUS     ROLES           AGE     VERSION
controlplane   NotReady   control-plane   3m37s   v1.27.0
node01         NotReady   <none>          35s     v1.27.0 

To install a network plugin, we will go with Flannel as the default choice. For inter-host communication, we will utilize the eth0 interface.

Please ensure that the Flannel manifest includes the appropriate options for this configuration.

Answer

Download the YAML file.

curl -LO https://raw.githubusercontent.com/flannel-io/flannel/v0.20.2/Documentation/kube-flannel.yml

Modify the file:

    args:
    - --ip-masq
    - --kube-subnet-mgr
    - --iface=eth0 

controlplane ~ ➜  k get no
NAME           STATUS     ROLES           AGE     VERSION
controlplane   NotReady   control-plane   3m37s   v1.27.0
node01         NotReady   <none>          35s     v1.27.0

controlplane ~ ➜  curl -LO https://raw.githubusercontent.com/flannel-io/flannel/v0.20.2/Documentation/kube-flannel.yml
% Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                Dload  Upload   Total   Spent    Left  Speed
100  4591  100  4591    0     0  34780      0 --:--:-- --:--:-- --:--:-- 34780

controlplane ~ ➜  vi kube-flannel.yml 

controlplane ~ ➜  kubectl apply -f kube-flannel.yml
namespace/kube-flannel created
clusterrole.rbac.authorization.k8s.io/flannel created
clusterrolebinding.rbac.authorization.k8s.io/flannel created
serviceaccount/flannel created
configmap/kube-flannel-cfg created
daemonset.apps/kube-flannel-ds created

Both nodes should change to Ready status now.

controlplane ~ ➜  k get no
NAME           STATUS   ROLES           AGE     VERSION
controlplane   Ready    control-plane   6m27s   v1.27.0
node01         Ready    <none>          3m25s   v1.27.0  

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