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Certified Kubernetes Application Developer (CKAD)

Preparation and study material for Certified Kubernetes Application Developer exam v1.30.

Reasoning

Having passed CKA earlier, it only makes sense to go for CKAD and CKS.

Aliases

Keep it simple:

alias k=kubectl
alias do="--dry-run=client -o yaml"
alias now="--force --grace-period 0"

alias kc="kubectl config"
alias kcgc="kubectl config get-contexts"
alias kccc="kubectl config current-context"

Allowed Kubernetes documentation resources

CKAD Environment

See https://docs.linuxfoundation.org/tc-docs/certification/tips-cka-and-ckad#cka-and-ckad-environment

There are four clusters (CKAD) that comprise the exam environment, made up of varying numbers of containers, as follows:

Cluster Members CNI Description
k8s 1 master, 2 worker flannel k8s cluster
dk8s 1 master, 1 worker flannel k8s cluster
nk8s 1 master, 2 worker calico k8s cluster
sk8s 1 master, 1 worker flannel k8s cluster

At the start of each task you'll be provided with the command to ensure you are on the correct cluster to complete the task.

Command-like tools kubectl, jq, tmux, curl, wget and man are pre-installed in all environments.

CKAD Exam Simulator

https://killer.sh/ckad

Do not sit the CKAD exam unless you get the perfect score and understand the solutions (regardless of the time taken to solve all questions).

CKAD Simulator

Prep: Cluster Installation and Configuration

This section is not part of CKAD exam objectives, however, we need to build a Kubernetes cluster to practise on.

Provision underlying infrastructure to deploy a Kubernetes cluster

We have a six-node (three control planes and three worker nodes) Kubernetes homelab cluster running Rocky Linux already.

For the purpose of our CKAD studies, we will create a new two-node cluster, with one control plane and one worker node, using Ubuntu 20.04 LTS. It makes sense to use a Debian-based distribution here because we have a RHEL-based homelab cluster already.

Libvirt/KVM nodes:

  • srv37-master: 2 vCPUs, 4GB RAM, 16GB disk, 10.11.1.37/24
  • srv38-node: 2 vCPUs, 4GB RAM, 16GB disk, 10.11.1.38/24

Provision a KVM guest for the control plane using PXE boot:

virt-install \
  --connect qemu+ssh://root@kvm1.hl.test/system \
  --name srv37-master \
  --network bridge=br0,model=virtio,mac=C0:FF:EE:D0:5E:37 \
  --disk path=/var/lib/libvirt/images/srv37.qcow2,size=16 \
  --pxe \
  --ram 4096 \
  --vcpus 2 \
  --os-type linux \
  --os-variant ubuntu20.04 \
  --sound none \
  --rng /dev/urandom \
  --virt-type kvm \
  --wait 0

When asked for an OS, select Ubuntu 20.04 LTS Server option.

PXE boot menu

Provision a KVM guest for the worker node using PXE boot:

virt-install \
  --connect qemu+ssh://root@kvm1.hl.test/system \
  --name srv38-node \
  --network bridge=br0,model=virtio,mac=C0:FF:EE:D0:5E:38 \
  --disk path=/var/lib/libvirt/images/srv38.qcow2,size=16 \
  --pxe \
  --ram 4096 \
  --vcpus 2 \
  --os-type linux \
  --os-variant ubuntu20.04 \
  --sound none \
  --rng /dev/urandom \
  --virt-type kvm \
  --wait 0

Use Kubeadm to install a basic cluster

Docs:

We will use kubeadm to install a Kubernetes v1.30 cluster.

Install container runtime on all nodes:

cat <<EOF | sudo tee /etc/modules-load.d/containerd.conf
overlay
br_netfilter
EOF

sudo modprobe overlay
sudo modprobe br_netfilter

cat <<EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
net.bridge.bridge-nf-call-iptables  = 1
net.ipv4.ip_forward                 = 1
net.bridge.bridge-nf-call-ip6tables = 1
EOF

sudo sysctl --system

Install containerd on all nodes:

sudo apt-get update
sudo apt-get -y install apt-transport-https ca-certificates curl gnupg lsb-release

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

sudo apt-get update
sudo apt-get -y install containerd.io

sudo mkdir -p /etc/containerd
containerd config default | sudo tee /etc/containerd/config.toml
sudo systemctl restart containerd

To use the systemd cgroup driver in /etc/containerd/config.toml with runc, set:

[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc]
  ...
  [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc.options]
    SystemdCgroup = true

sudo sed -i 's/            SystemdCgroup =.*/            SystemdCgroup = true/g' /etc/containerd/config.toml

Make sure to restart containerd:

sudo systemctl restart containerd

Install kubeadm, kubelet and kubectl (v1.30):

sudo mkdir -p -m 755 /etc/apt/keyrings
curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.30/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring-1.30.gpg

echo "deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring-1.30.gpg] https://pkgs.k8s.io/core:/stable:/v1.30/deb/ /" | sudo tee /etc/apt/sources.list.d/kubernetes-1.30.list

sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl
sudo systemctl enable kubelet

Initialise the control plane node. Set pod network CIDR based on the CNI that you plan to install later:

  • Calico - 192.168.0.0/16
  • Flannel - 10.244.0.0/16
  • Weave Net - 10.32.0.0/12

We are going to use Calico to support network policies, hence 192.168.0.0/16.

sudo kubeadm init \
  --kubernetes-version "1.30.1" \
  --pod-network-cidr "192.168.0.0/16"

Configure kubectl access on the control plane:

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

Run the output of the init command on the worker node:

kubeadm join 10.11.1.37:6443 --token e3mo9r.tul2hff2tx3ykkj7 \
  --discovery-token-ca-cert-hash sha256:8048cdef7090a3dec68ffe83fc329111a2efb83523ec659e0e9d5d4ebb2d19f7

Install a pod network to the cluster. To install Calico, run the following:

kubectl apply -f kubectl apply -f "https://projectcalico.docs.tigera.io/manifests/calico.yaml"

Check the cluster to make sure that all nodes are running and ready:

kubectl get nodes
NAME    STATUS   ROLES           AGE   VERSION   INTERNAL-IP   EXTERNAL-IP   OS-IMAGE             KERNEL-VERSION      CONTAINER-RUNTIME
srv37   Ready    control-plane   18h   v1.30.1   10.11.1.37    <none>        Ubuntu 20.04.6 LTS   5.4.0-196-generic   containerd://1.7.22
srv38   Ready    <none>          18h   v1.30.1   10.11.1.38    <none>        Ubuntu 20.04.6 LTS   5.4.0-196-generic   containerd://1.7.22

Now that we have a cluster running, we can start with the exam objectives.

Prep: Install Podman and Helm

While installation of these tools is not part of the CKAD exam objectives, we are going to need to have them on our system in order to solve tasks.

Use these commands to install Podman on Ubuntu 20.04:

VERSION_ID="20.04"
echo "deb http://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/xUbuntu_${VERSION_ID}/ /" | sudo tee /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list
curl -fsSL https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable/xUbuntu_${VERSION_ID}/Release.key | sudo apt-key add -
sudo apt-get update
sudo apt-get install -y podman

Use these commands to install Helm on Ubuntu 20.04:

sudo apt install -y apt-transport-https software-properties-common
curl -fsSL https://baltocdn.com/helm/signing.asc | sudo apt-key add -
sudo add-apt-repository -y "deb https://baltocdn.com/helm/stable/debian/ all main"
sudo apt-get update
sudo apt-get install -y helm

Application Design and Build

Unless stated otherwise, all Kubernetes resources should be created in the ckad namespace.

Define, build and modify container images

Study material for this section is very similar to that of the Red Hat's EX180 exam that I had taken previously.

Before you start with this section, please log in to Red Hat Developer portal and download the jboss-eap-7.4.0.zip file to your working directory. See the weblink below, do note that it requires a free Red Hat account:

https://developers.redhat.com/content-gateway/file/jboss-eap-7.4.0.zip

Also create a Docker Hub account if you don't have one.

Task 1

As a certified application developer, you should be able to define and build container images. Write a Dockerfile to containerise a JBoss EAP 7.4 application to meet all of the following requirements (listed in no particular order):

  1. Use tag 8.7 of Red Hat Universal Base Image 8 ubi8 from the Docker Hub registry docker.io/redhat as a base.
  2. Install the java-1.8.0-openjdk-devel package.
  3. Create a system group for jboss with a GID of 1100.
  4. Create a system user for jboss with a UID 1100.
  5. Set the jboss user’s home directory to /opt/jboss.
  6. Set the working directory to jboss user's home directory.
  7. Recursively change the ownership of the jboss user’s home directory to jboss:jboss.
  8. Expose port 8080.
  9. Make the container run as the jboss user.
  10. Unpack the jboss-eap-7.4.0.zip file to the /opt/jboss directory.
  11. Set the environment variable JBOSS_HOME to /opt/jboss/jboss-eap-7.4.
  12. Start container with the following executable: /opt/jboss/jboss-eap-7.4/bin/standalone.sh -b 0.0.0.0 -c standalone-full-ha.xml.

Solution 1

This is how the Dockerfile should look like. Comments are provided for references.

# Use base image
FROM docker.io/redhat/ubi8:8.7

# Install the java-1.8.0-openjdk-devel package
# We also need the unzip package to unpack the JBoss .zip archive
RUN yum install -y java-1.8.0-openjdk-devel unzip && yum clean all

# Create a system user and group for jboss, they both have a UID and GID of 1100
# Set the jboss user's home directory to /opt/jboss
RUN groupadd -r -g 1100 jboss && useradd -u 1100 -r -m -g jboss -d /opt/jboss -s /sbin/nologin jboss

# Set the environment variable JBOSS_HOME to /opt/jboss/jboss-eap-7.4.0
ENV JBOSS_HOME="/opt/jboss/jboss-eap-7.4"

# Set the working directory to jboss' user home directory
WORKDIR /opt/jboss

# Unpack the jboss-eap-7.4.0.zip file to the /opt/jboss directory
ADD ./jboss-eap-7.4.0.zip /opt/jboss
RUN unzip /opt/jboss/jboss-eap-7.4.0.zip

# Recursively change the ownership of the jboss user's home directory to jboss:jboss
# Make sure to RUN the chown after the ADD command and before it, as ADD will
# create new files and directories with a UID and GID of 0 by default
RUN chown -R jboss:jboss /opt/jboss

# Make the container run as the jboss user
USER jboss

# Expose JBoss port
EXPOSE 8080

# Start JBoss, use the exec form which is the preferred form
ENTRYPOINT ["/opt/jboss/jboss-eap-7.4/bin/standalone.sh", "-b", "0.0.0.0", "-c", "standalone-full-ha.xml"]

Task 2

Build the container image using Podman from the Dockerfile you have created in task 1.

  1. Name the image as ckadstudy-jboss-eap, add a tag of 7.4.0-podman, and push the image to your Docker Hub's registry account.
  2. Also tag the images as latest and push to Docker Hub.
  3. Use Podman to run a container named jboss-from-dockerfile, which keeps running in the background, using image ckadstudy-jboss-eap:7.4.0-podman. Run the container as a regular user and not as root. Expose container port 8080.
  4. Write logs of the container jboss-from-dockerfile to file /tmp/jboss-from-dockerfile.log.

Solution 2

Make sure that the file jboss-eap-7.4.0.zip has been downloaded and is in the working directory:

ls -1
Dockerfile
jboss-eap-7.4.0.zip

Build the image:

podman build -t ckadstudy-jboss-eap:7.4.0-podman -t ckadstudy-jboss-eap:latest .

View all local images:

podman images
REPOSITORY                     TAG           IMAGE ID      CREATED             SIZE
localhost/ckadstudy-jboss-eap  7.4.0-podman  d0e3daccd5d3  About a minute ago  1.44 GB
localhost/ckadstudy-jboss-eap  latest        d0e3daccd5d3  About a minute ago  1.44 GB
docker.io/redhat/ubi8          8.7           270f760d3d04  2 weeks ago         214 MB

Tag the images, log into Docker Hub registry and then push the images to it:

podman tag localhost/ckadstudy-jboss-eap:7.4.0-podman lisenet/ckadstudy-jboss-eap:7.4.0-podman
podman tag localhost/ckadstudy-jboss-eap:latest lisenet/ckadstudy-jboss-eap:latest
podman login docker.io
podman push lisenet/ckadstudy-jboss-eap:7.4.0-podman
podman push lisenet/ckadstudy-jboss-eap:latest

Run a container and expose port 8080:

podman run -d --name jboss-from-dockerfile -p 8080:8080 localhost/ckadstudy-jboss-eap:7.4.0-podman
podman ps
CONTAINER ID  IMAGE                                       COMMAND     CREATED         STATUS             PORTS                   NAMES
0ad455a21fa2  localhost/ckadstudy-jboss-eap:7.4.0-podman              40 seconds ago  Up 40 seconds ago  0.0.0.0:8080->8080/tcp  jboss-from-dockerfile

Verify the port is accessible:

curl -s 127.0.0.1:8080 | grep Welcome
    <title>Welcome to JBoss EAP 7</title>
      <h1>Welcome to JBoss EAP 7</h1>

Write logs to /tmp/jboss-from-dockerfile.log file:

podman logs jboss-from-dockerfile | tee /tmp/jboss-from-dockerfile.log

Understand Jobs and CronJobs

Docs:

Task 3

  1. Create a job called pi in ckad namespace.
  2. This job should run image perl:5.34.0 and execute command ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"].
  3. It should run a total of 8 times and should execute 2 runs in parallel.
  4. Set restartPolicy to Never.

Solution 3

Create a job template:

kubeclt create job pi --image=perl:5.34.0 \
  --dry-run=client -o yaml -n ckad > pi-job.yaml

Edit the file pi-job.yaml and add missing resources:

---
apiVersion: batch/v1
kind: Job
metadata:
  name: pi
  namespace: ckad
spec:
  completions: 8
  parallelism: 2
  template:
    spec:
      containers:
      - image: perl:5.34.0
        name: pi
        command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]
      restartPolicy: Never

Create the job:

kubectl apply -f pi-job.yaml

Verify:

kubectl get job -n ckad -o wide
NAME  COMPLETIONS   DURATION   AGE   CONTAINERS   IMAGES         SELECTOR
pi    2/8           17s        17s   pi           perl:5.34.0    controller-uid=adbaa84e

Task 4

  1. Create a cronjob called crondate in ckad namespace.
  2. This job should run image busybox:1.35 and execute command date every 2 minutes.
  3. Set successfulJobsHistoryLimit to 5 and failedJobsHistoryLimit to 3.
  4. Set concurrencyPolicy to Replace.

Solution 4

Create a job template:

kubectl create cronjob crondate --image=busybox:1.35 --schedule="*/2 * * * *" \
  --dry-run=client -o yaml -n ckad -- date > crondate.yaml

Edit the file crondate.yaml and add missing resources:

---
apiVersion: batch/v1
kind: CronJob
metadata:
  name: crondate
  namespace: ckad
spec:
  successfulJobsHistoryLimit: 5
  failedJobsHistoryLimit: 3
  concurrencyPolicy: Replace
  jobTemplate:
    metadata:
      name: crondate
    spec:
      template:
        spec:
          containers:
          - command:
            - date
            image: busybox:1.35
            name: crondate
          restartPolicy: OnFailure
  schedule: '*/2 * * * *'

Create the cronjob:

kubectl apply -f crondate.yaml

Verify:

kubectl get cronjob -o wide -n ckad
NAME       SCHEDULE      SUSPEND   ACTIVE   LAST SCHEDULE   AGE   CONTAINERS   IMAGES         SELECTOR
crondate   */2 * * * *   False     0        19s             83s   crondate     busybox:1.35   <none>

Understand multi-container Pod design patterns (sidecar, init and others)

Docs: https://kubernetes.io/docs/concepts/workloads/pods/init-containers/

Task 5

  1. Create a pod called web-multi-container that has three containers (see below).
  2. A container named main running nginx:alpine image. This container should expose port 80.
  3. A sidecar container named sidecar-updater running busybox:1.35 image. The sidecar container run the following command: ["sh","-c","while true; do date | tee /usr/share/nginx/html/index.html; sleep 1; done"].
  4. An initContainer named init-health running busybox:1.35.0 image. The init container runs the following command: ["sh","-c","echo live > /usr/share/nginx/html/health"].
  5. All containers inside the pod should mount an emptyDir volume named webroot, the mount path is /usr/share/nginx/html.

Solution 5

Create a container template:

kubectl run web-multi-container --image=nginx:alpine --port=80 \
  --dry-run=client -o yaml -n ckad > web-multi-container.yaml

Edit the file web-multi-container.yaml and add an init container as well as a sidecar one, also add a volume.

---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: web-multi-container
  name: web-multi-container
  namespace: ckad
spec:
  volumes:
    - name: webroot
      emptyDir: {}
  containers:
  - image: nginx:alpine
    name: main
    ports:
    - containerPort: 80
    volumeMounts:
      - mountPath: /usr/share/nginx/html
        name: webroot
  - image: busybox:1.35
    name: sidecar-updater
    command: ["sh","-c","while true; do date | tee /usr/share/nginx/html/index.html; sleep 1; done"]
    volumeMounts:
      - mountPath: /usr/share/nginx/html
        name: webroot
  initContainers:
  - image: busybox:1.35
    name: init-health
    command: ["sh","-c","echo live > /usr/share/nginx/html/health"]
    volumeMounts:
      - mountPath: /usr/share/nginx/html
        name: webroot

Deploy the pod and verify that 2 containers are running:

kubectl apply -f web-multi-container.yaml
kubectl get po/web-multi-container -n ckad
NAME                  READY   STATUS    RESTARTS   AGE
web-multi-container   2/2     Running   0          2m15s

Also verify that webroot files have been created:

kubectl exec web-multi-container -c main -n ckad -- cat /usr/share/nginx/html/health
live
kubectl exec web-multi-container -c main -n ckad -- cat /usr/share/nginx/html/index.html
Tue Feb 28 20:20:52 UTC 2023

Utilise persistent and ephemeral volumes

Docs:

Task 6

  1. Create a persistent volume named pv-httpd-webroot with the following specifications:
    • Storage class name is set to manual.
    • Access mode is set to ReadWriteMany.
    • Storage capacity is set to 64Mi.
    • Persistent volume reclaim policy is set to Retain.
    • Volume mode is set to Filesystem.
    • hostPath is set to /mnt/data.
  2. Create a persistent volume claim object pvc-httpd-webroot.
  3. Create a deployment object httpd-persistent consisting of 2 pods, each containing a single httpd:2.4 container.
  4. Configure deployment to use the persistent volume claim as a volume where mountPath is set to /usr/local/apache2/htdocs.
  5. Exec a command in either of the httpd containers and create a blank file /usr/local/apache2/htdocs/blank.html.
  6. Delete the deployment object httpd-persistent.
  7. Create the deployment object httpd-persistent again.
  8. Exec a command in either of the httpd containers to verify that the file /usr/local/apache2/htdocs/blank.html exists.

Solution 6

Create a persistent volume definition:

cat > pv-httpd-webroot.yaml <<EOF
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-httpd-webroot
spec:
  capacity:
    storage: 64Mi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  storageClassName: manual
  hostPath:
    path: "/mnt/data"
EOF
kubectl apply -f pv-httpd-webroot.yaml
kubectl get pv
NAME               CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
pv-httpd-webroot   64Mi       RWX            Retain           Available           manual                  15s
cat > pvc-httpd-webroot.yaml <<EOF
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-httpd-webroot
  namespace: ckad
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 64Mi
EOF
kubectl apply -f pvc-httpd-webroot.yaml
kubectl get pvc -n ckad
NAME                STATUS   VOLUME             CAPACITY   ACCESS MODES   STORAGECLASS   AGE
pvc-httpd-webroot   Bound    pv-httpd-webroot   64Mi       RWX            manual         8s
kubectl create deploy httpd-persistent \
  --image=httpd:2.4 --replicas=2 \
  --dry-run=client -o yaml -n ckad > httpd-persistent.yaml

Edit the file httpd-persistent.yaml and add volumes and volumeMounts sections:

---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: httpd-persistent
  name: httpd-persistent
  namespace: ckad
spec:
  replicas: 2
  selector:
    matchLabels:
      app: httpd-persistent
  template:
    metadata:
      labels:
        app: httpd-persistent
    spec:
      containers:
      - image: httpd:2.4
        name: httpd
        volumeMounts:
          - mountPath: "/usr/local/apache2/htdocs"
            name: pvc-httpd-persistent
      volumes:
      - name: pvc-httpd-persistent
        persistentVolumeClaim:
          claimName: pvc-httpd-webroot

Create deployment:

kubectl apply -f httpd-persistent.yaml

Create a blank file:

kubectl -n ckad exec $(k get po -n ckad | grep httpd-persistent | cut -d" " -f1 | head -n1) -- touch /usr/local/apache2/htdocs/blank.html

Delete and re-create the deployment:

kubectl delete deploy/httpd-persistent -n ckad
kubectl apply -f httpd-persistent.yaml

Verify the blank file exists:

kubectl -n ckad exec $(k get po -n ckad | grep httpd-persistent | cut -d" " -f1 | head -n1) -- ls /usr/local/apache2/htdocs/blank.html
/usr/local/apache2/htdocs/blank.html

Declarative YAML:

---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-httpd-webroot
spec:
  capacity:
    storage: 64Mi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  storageClassName: manual
  hostPath:
    path: "/mnt/data"
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-httpd-webroot
  namespace: ckad
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 64Mi
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: httpd-persistent
  name: httpd-persistent
  namespace: ckad
spec:
  replicas: 2
  selector:
    matchLabels:
      app: httpd-persistent
  template:
    metadata:
      labels:
        app: httpd-persistent
    spec:
      containers:
      - image: httpd:2.4
        name: httpd
        volumeMounts:
          - mountPath: "/usr/local/apache2/htdocs"
            name: pvc-httpd-persistent
      volumes:
      - name: pvc-httpd-persistent
        persistentVolumeClaim:
          claimName: pvc-httpd-webroot

Application Deployment

Unless stated otherwise, all Kubernetes resources should be created in the ckad namespace.

Use Kubernetes primitives to implement common deployment strategies (blue/green or canary)

Docs: https://kubernetes.io/docs/concepts/workloads/controllers/deployment/

Task 7: Blue/Green Deployment

  1. Create a deployment httpd-blue that uses image lisenet/httpd-pii-demo:0.2 and has these labels: app=front-end and release=blue. The deployment should run 2 replicas and expose port 80.
  2. Create a service httpd-blue-green that exposes the deployment httpd-blue on port 80.
  3. Create a deployment httpd-green that uses image lisenet/httpd-pii-demo:0.3 and has these labels: app=front-end and release=green. The deployment should run 2 replicas and expose port 80.
  4. Update service httpd-blue-green configuration to route traffic to deployment httpd-green.

Solution 7

Create a deployment template:

kubectl create deploy httpd-blue --image="lisenet/httpd-pii-demo:0.2" \
  --replicas=2 --port=80 \
  --dry-run=client -o yaml -n ckad > httpd-blue.yaml

Edit the file httpd-blue.yaml and add required labels:

---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: front-end
    release: blue
  name: httpd-blue
  namespace: ckad
spec:
  replicas: 2
  selector:
    matchLabels:
      app: front-end
      release: blue
  template:
    metadata:
      labels:
        app: front-end
        release: blue
    spec:
      containers:
      - image: lisenet/httpd-pii-demo:0.2
        name: httpd-pii-demo
        ports:
        - containerPort: 80

Create the blue deployment:

kubectl apply -f httpd-blue.yaml

Expose the deployment:

kubectl expose deployment httpd-blue --name=httpd-blue-green -n ckad

Create a new green deployment file by copying the existing blue one, and update the release label as well as container image:

cp httpd-blue.yaml httpd-green.yaml
sed -i 's/blue/green/g' httpd-green.yaml
sed -i 's/httpd-pii-demo:0.2/httpd-pii-demo:0.3/g' httpd-green.yaml

Create the green deployment:

kubectl apply -f httpd-green.yaml

Verify:

kubectl get deploy -n ckad
NAME          READY   UP-TO-DATE   AVAILABLE   AGE
httpd-blue    2/2     2            2           9m22s
httpd-green   2/2     2            2           63s

Edit the service:

kubectl edit svc httpd-blue-green -n ckad

Update selector by chaging release: blue to release: green:

  selector:
    app: front-end
    release: green

Task 8: Canary Deployment

  1. Create a deployment webapp-canary-blue that uses image kodekloud/webapp-color and has a label of app=webapp. The deployment should run 3 replicas and expose port 8080. Configure the deployment so that the underlying container has the environent variable APP_COLOR set to the value of blue.
  2. Create a deployment webapp-canary-green that uses image kodekloud/webapp-color and has a label of app=webapp. The deployment should expose port 8080. Configure the deployment so that the underlying container has the environent variable APP_COLOR set to the value of green.
  3. Create a service httpd-canary that load balances request from both deployments on port 8080.
  4. Configure the deployment webapp-canary-green so that the service httpd-canary sends 75% of requests to deployment httpd-canary-blue and 25% to deployment httpd-canary-green.

Solution 8

Create a deployment template:

kubectl create deploy webapp-canary-blue --image="kodekloud/webapp-color" \
  --replicas=3 --port=8080 \
  --dry-run=client -o yaml -n ckad > webapp-canary-blue.yaml

Edit the file webapp-canary-blue.yaml and add required labels, also add the evironment variable:

---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: webapp
  name: webapp-canary-blue
  namespace: ckad
spec:
  replicas: 3
  selector:
    matchLabels:
      app: webapp
  template:
    metadata:
      labels:
        app: webapp
    spec:
      containers:
      - image: kodekloud/webapp-color
        name: webapp-color
        ports:
        - containerPort: 8080
        env: 
        - name: APP_COLOR
          value: "blue"

Create the blue deployment:

kubectl apply -f webapp-canary-blue.yaml

Create a new green deployment file by copying the existing blue one and update the release label:

cp webapp-canary-blue.yaml webapp-canary-green.yaml
sed -i 's/blue/green/g' webapp-canary-green.yaml

Create the green deployment:

kubectl apply -f webapp-canary-green.yaml

Verify:

kubectl get deploy -n ckad
NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
webapp-canary-blue    3/3     3            3           32m
webapp-canary-green   3/3     3            3           32m
kubectl get po --show-labels -n ckad
NAME                                   READY   STATUS    RESTARTS   AGE   LABELS
webapp-canary-blue-7f767d4c74-nh8zm    1/1     Running   0          32m   app=webapp,pod-template-hash=7f767d4c74
webapp-canary-blue-7f767d4c74-zkx6n    1/1     Running   0          32m   app=webapp,pod-template-hash=7f767d4c74
webapp-canary-blue-7f767d4c74-zm4ds    1/1     Running   0          32m   app=webapp,pod-template-hash=7f767d4c74
webapp-canary-green-5bb956f674-rvxnw   1/1     Running   0          32m   app=webapp,pod-template-hash=5bb956f674
webapp-canary-green-5bb956f674-rxhv7   1/1     Running   0          32m   app=webapp,pod-template-hash=5bb956f674
webapp-canary-green-5bb956f674-xmgtz   1/1     Running   0          32m   app=webapp,pod-template-hash=5bb956f674

Create a service template:

kubectl expose deployment webapp-canary-blue \
  --name=httpd-canary --port=8080 \
  --dry-run=client -o yaml -n ckad > httpd-canary.yaml

Edit the file httpd-canary.yaml and make sure that the service uses the right label app: webapp:

---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: webapp
  name: httpd-canary
  namespace: ckad
spec:
  ports:
  - port: 8080
    protocol: TCP
    targetPort: 8080
  selector:
    app: webapp

Create the service:

kubectl apply -f httpd-canary.yaml

Verify:

kubectl get svc -o wide -n ckad
NAME           TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE   SELECTOR
httpd-canary   ClusterIP   10.100.237.144   <none>        8080/TCP  33m   app=webapp

Because we have the same amount of replicas for each deployment, the service should load balance requests fairly equally (50%/50%). In order to achieve 75%/25%, we are going to scale the green deployment replicas down from 3 to 1.

kubectl scale deploy webapp-canary-green --replicas=1 -n ckad

If we make a large number (e.g. 100) of requests to the service, we should see approximately 75% being routed to the blue deployment:

for i in $(seq 1 100); do curl -s http://10.100.237.144:8080 | grep webapp;done | grep -c blue
73

Understand Deployments and how to perform rolling updates

Docs: https://kubernetes.io/docs/concepts/workloads/controllers/deployment/#scaling-a-deployment

Task 9

  1. Create a deployment object nginx-deployment consisting of 2 pods containing a single nginx:1.21 container.
  2. Increase the deployment size by adding 1 additional pod.
  3. Update deployment container image to nginx:1.21.0.0.
  4. Roll back a broken deployment to the previous version.

Solution 9

kubectl create deploy nginx-deployment --image=nginx:1.21 --replicas=2 -n ckad
kubectl scale deploy nginx-deployment --replicas=3 -n ckad
kubectl set image deployment/nginx-deployment nginx=nginx:1.21.1.1 -n ckad
kubectl rollout history deploy nginx-deployment -n ckad
kubectl rollout undo deploy nginx-deployment -n ckad

Declarative YAML (initial):

---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx-deployment
  name: nginx-deployment
  namespace: ckad
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx-deployment
  template:
    metadata:
      labels:
        app: nginx-deployment
    spec:
      containers:
      - image: nginx:1.21
        name: nginx

Declarative YAML (updated):

---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx-deployment
  name: nginx-deployment
  namespace: ckad
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx-deployment
  template:
    metadata:
      labels:
        app: nginx-deployment
    spec:
      containers:
      - image: nginx:1.21.1.1
        name: nginx

Use the Helm package manager to deploy existing packages

Docs: https://helm.sh/docs/

Task 10

  1. Add Helm repository with a name of prometheus-community and URL https://prometheus-community.github.io/helm-charts.
  2. Use Helm to deploy a Prometheus server. Install a new release prometheus of chart prometheus-community/prometheus and chart version 19.0.0.
  3. Customise Helm deployment and set Prometheus data retention to 1h, disable Prometheus server persistent volume, also disable deployment of Alertmanager. Set these via Helm-values during install.
  4. Resources should be deployed into monitoring namespace.
  5. Upgrade Helm deployment in order to update Prometheus server version to 2.41.0 (application version). You can use any Helm chart version that provides application version 2.41.0.
  6. Delete Helm prometheus release.

Solution 10

Add Helm repository:

helm repo add prometheus-community https://prometheus-community.github.io/helm-charts

Work out what values are available for the given chart version:

helm show values prometheus-community/prometheus --version 19.0.0

Create a monitoring namespace and deploy Prometheus:

kubectl create ns monitoring

helm install prometheus \
  prometheus-community/prometheus \
  --namespace monitoring \
  --version 19.0.0 \
  --set retention=1h \
  --set server.persistentVolume.enabled=false \
  --set alertmanager.enabled=false

Verify:

helm ls -aA
NAME      	NAMESPACE 	REVISION	UPDATED                                	STATUS  	CHART            	APP VERSION
prometheus	monitoring	1       	2023-03-01 20:29:45.061483758 +0000 UTC	deployed	prometheus-19.0.0	v2.40.5

Find out what application version comes with Helm chart 19.0.0:

helm search repo prometheus-community/prometheus --version 19.0.0
NAME                           	CHART VERSION	APP VERSION	DESCRIPTION                                       
prometheus-community/prometheus	19.0.0       	v2.40.5    	Prometheus is a monitoring system and time seri...

List all releases and search for application version 2.41.0:

helm search repo prometheus-community/prometheus -l | grep 2.41.0
prometheus-community/prometheus                   	19.7.2       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.7.1       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.6.1       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.6.0       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.5.0       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.4.0       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.3.3       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.3.2       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.3.1       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.3.0       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.2.2       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.2.1       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.2.0       	v2.41.0    	Prometheus is a monitoring system and time seri...
prometheus-community/prometheus                   	19.1.0       	v2.41.0    	Prometheus is a monitoring system and time seri...

We can use any chart version that provides application version 2.41.0. We will go for chart 19.7.2:

helm upgrade --install \
  prometheus \
  prometheus-community/prometheus \
  --namespace monitoring \
  --version 19.7.2 \
  --set retention=1h \
  --set server.persistentVolume.enabled=false \
  --set alertmanager.enabled=false

Verify:

helm ls -aA
NAME      	NAMESPACE 	REVISION	UPDATED                               	STATUS  	CHART            	APP VERSION
prometheus	monitoring	2       	2023-03-01 20:31:28.52568917 +0000 UTC	deployed	prometheus-19.7.2	v2.41.0

Delete prometheus release:

helm -n monitoring uninstall prometheus

Note: if you somehowmanage to break your release, then by default, releases in pending-upgrade state won't be listed. However, you can show all to find and delete the broken one:

helm ls -a

Application Observability and Maintenance

Unless stated otherwise, all Kubernetes resources should be created in the ckad namespace.

Understand API deprecations

Docs: https://kubernetes.io/docs/reference/using-api/deprecation-guide/

Task 11

  1. Use provided YAML file below to create a role. Fix any issues.
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: broken-role
  namespace: ckad
rules:
  - verbs:
      - "get"
      - "create"
      - "delete"
    apiGroups:
      - ''
    resources:
      - services/proxy

Solution 11

Create a role template:

cat > broken-role.yaml <<EOF
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: broken-role
  namespace: ckad
rules:
  - verbs:
      - "get"
      - "create"
      - "delete"
    apiGroups:
      - ''
    resources:
      - services/proxy
EOF

Apply configuration from file:

kubectl apply -f broken-role.yaml

error: resource mapping not found for name: "broken-role" namespace: "ckad" from "./broken-role.yaml": no matches for kind "Role" in version "rbac.authorization.k8s.io/v1beta1"
ensure CRDs are installed first

The rbac.authorization.k8s.io/v1beta1 API version of ClusterRole, ClusterRoleBinding, Role and RoleBinding is no longer served as of v1.22. Fix the API version:

sed -i 's#rbac.authorization.k8s.io/v1beta1#rbac.authorization.k8s.io/v1#g#' broken-role.yaml

Apply the config again:

kubectl apply -f broken-role.yaml
role.rbac.authorization.k8s.io/broken-role created

Implement probes and health checks

Docs: https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/

Task 12

  1. Create a pod httpd-liveness-readiness that uses lisenet/httpd-healthcheck:1.0.0 image.
  2. Configure a readinessProbe for an httpGet check using a path of /index.html and port 10001.
  3. Configure a livenessProbe for a TCP check on port 10001.
  4. Set initialDelaySeconds to 5. The probes should be performed every 10 seconds.

Solution 12

Create a pod template:

kubectl run httpd-liveness-readiness --image=lisenet/httpd-healthcheck:1.0.0 \
  --dry-run=client -o yaml -n ckad > httpd-liveness-readiness.yaml

Edit the file httpd-liveness-readiness.yaml and add probes:

---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: httpd-liveness-readiness
  name: httpd-liveness-readiness
  namespace: ckad
spec:
  containers:
  - image: lisenet/httpd-healthcheck:1.0.0
    name: httpd-liveness-readiness
    readinessProbe:
      httpGet:
        path: /index.html
        port: 10001
      initialDelaySeconds: 5
      periodSeconds: 10
    livenessProbe:
      tcpSocket:
        port: 10001
      initialDelaySeconds: 5
      periodSeconds: 10

Deploy the pod:

kubectl apply -f httpd-liveness-readiness.yaml

Verify:

kubectl describe po/httpd-liveness-readiness -n ckad | egrep "Liveness|Readiness"
    Liveness:       tcp-socket :10001 delay=5s timeout=1s period=10s #success=1 #failure=3
    Readiness:      http-get http://:10001/index.html delay=5s timeout=1s period=10s #success=1 #failure=3

Use provided tools to monitor Kubernetes applications

Docs: https://kubernetes.io/docs/concepts/cluster-administration/system-metrics/

Utilise container logs

Docs: https://kubernetes.io/docs/concepts/cluster-administration/logging/

Dump pod logs to stdout:

kubectl logs ${POD_NAME}

Dump pod logs for a deployment (single-container case):

kubectl logs deploy/${DEPLOYMENT_NAME}

Dump pod logs for a deployment (multi-container case):

kubectl logs deploy/${DEPLOYMENT_NAME} -c ${CONTAINER_NAME}

Debugging in Kubernetes

Docs:

The first step in troubleshooting is triage. What is the problem? Is it your Pods, your Replication Controller or your Service?

Check the current state of the pod and recent events with the following command:

kubectl describe pods ${POD_NAME}

Next, verify that there are endpoints for the service. For every Service object, the apiserver makes an endpoints resource available. You can view this resource with:

kubectl get endpoints ${SERVICE_NAME}

Application Environment, Configuration and Security

Unless stated otherwise, all Kubernetes resources should be created in the ckad namespace.

Discover and use resources that extend Kubernetes (CRD)

Docs: https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/

Task 13

  1. A CustomResourceDefinition YAML file is provided below. Use it to create the resource.
# customresourcedefinition.yaml
---
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  # name must match the spec fields below, and be in the form: <plural>.<group>
  name: crontabs.stable.example.com
spec:
  # group name to use for REST API: /apis/<group>/<version>
  group: stable.example.com
  # list of versions supported by this CustomResourceDefinition
  versions:
    - name: v1
      # Each version can be enabled/disabled by Served flag.
      served: true
      # One and only one version must be marked as the storage version.
      storage: true
      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              properties:
                cronSpec:
                  type: string
                image:
                  type: string
                replicas:
                  type: integer
  # either Namespaced or Cluster
  scope: Namespaced
  names:
    # plural name to be used in the URL: /apis/<group>/<version>/<plural>
    plural: crontabs
    # singular name to be used as an alias on the CLI and for display
    singular: crontab
    # kind is normally the CamelCased singular type. Your resource manifests use this.
    kind: CronTab
    # shortNames allow shorter string to match your resource on the CLI
    shortNames:
    - ct

Solution 13

Install CRD:

kubectl apply -f customresourcedefinition.yaml

Verify:

kubectl get customresourcedefinition
NAME                          CREATED AT
crontabs.stable.example.com   2023-03-02T19:12:35Z

Understand authentication, authorisation and admission control

Docs: https://kubernetes.io/docs/reference/access-authn-authz/rbac/

See task 19.

Understanding and defining resource requirements, limits and quotas

Docs:

Task 14

  1. Create a pod httpd-resource-limits that uses lisenet/httpd-healthcheck:1.0.0 image.
  2. Set the pod memory request to 40Mi and memory limit to 128Mi.
  3. Set the pod CPU request to 10m and CPU limit to 50m.

Solution 14

Create a pod template:

kubectl run httpd-resource-limits --image=lisenet/httpd-healthcheck:1.0.0 \
  --dry-run=client -o yaml -n ckad > httpd-resource-limits.yaml

Edit the file httpd-resource-limits.yaml and add resources section:

---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: httpd-resource-limits
  name: httpd-resource-limits
  namespace: ckad
spec:
  containers:
  - image: lisenet/httpd-healthcheck:1.0.0
    name: httpd-resource-limits
    resources:
      requests:
        cpu: 10m
        memory: 40Mi
      limits:
        cpu: 50m
        memory: 128Mi

Deploy the pod:

kubectl apply -f httpd-resource-limits.yaml

Verify:

kubectl describe po/httpd-resource-limits -n ckad | egrep -A2 "Limits|Requests"
    Limits:
      cpu:     50m
      memory:  128Mi
    Requests:
      cpu:        10m
      memory:     40Mi

Task 15

  1. Create a namespace ckad-memlimit with a container memory limit of 30Mi.
  2. Create a pod httpd-memlimit that uses lisenet/httpd-healthcheck:1.0.0 image in the ckad-memlimit namespace, and set the pod memory request to 100Mi.
  3. Observe the error.

Solution 15

Create a namespace:

kubectl create ns ckad-memlimit
cat > ckad-memlimit.yaml <<EOF
---
apiVersion: v1
kind: LimitRange
metadata:
  name: ckad-memlimit
  namespace: ckad-memlimit
spec:
  limits:
  - max:
      memory: 30Mi
    type: Container
EOF
kubectl apply -f ckad-memlimit.yaml

kubectl run httpd-memlimit --image=lisenet/httpd-healthcheck:1.0.0 \
  --dry-run=client -o yaml -n ckad-memlimit > httpd-memlimit.yaml

Edit the file httpd-memlimit.yaml and add resources section:

---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: httpd-memlimit
  name: httpd-memlimit
  namespace: ckad-memlimit
spec:
  containers:
  - image: lisenet/httpd-healthcheck:1.0.0
    name: httpd-memlimit
    resources:
      requests:
        memory: 100Mi

Deploy the pod:

kubectl apply -f httpd-healthcheck-memlimit.yaml
The Pod "httpd-memlimit" is invalid: spec.containers[0].resources.requests: Invalid value: "100Mi": must be less than or equal to memory limit

Understand ConfigMaps

Docs: https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/

Task 16

Configure application to use a ConfigMap.

  1. Create a configmap webapp-color that has the following key=value pair:
    • key = color
    • value = blue
  2. Create a pod webapp-color that uses kodekloud/webapp-color image.
  3. Configure the pod so that the underlying container has the environent variable APP_COLOR set to the value of the configmap.
  4. Check pod logs to ensure that the variable has been set correctly.

Solution 16

Create a config map and a pod template:

kubectl create cm webapp-color --from-literal=color=blue -n ckad
kubectl run webapp-color --image=kodekloud/webapp-color \
  --dry-run=client -o yaml -n ckad > webapp-color.yaml

Edit the file webapp-color.yaml and add env section:

---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: webapp-color
  name: webapp-color
  namespace: ckad
spec:
  containers:
  - image: kodekloud/webapp-color
    name: webapp-color
    env:
      # Define the environment variable
      - name: APP_COLOR
        valueFrom:
          configMapKeyRef:
            # The ConfigMap containing the value you want to assign to APP_COLOR
            name: webapp-color
            # Specify the key associated with the value
            key: color

Deploy the pod and validate:

kubectl apply -f webapp-color.yaml
kubectl logs webapp-color -n ckad | grep "Color from environment variable"

Declarative YAML:

---
apiVersion: v1
data:
  color: blue
kind: ConfigMap
metadata:
  name: webapp-color
  namespace: ckad
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: webapp-color
  name: webapp-color
  namespace: ckad
spec:
  containers:
  - image: kodekloud/webapp-color
    name: webapp-color
    env:
      # Define the environment variable
      - name: APP_COLOR
        valueFrom:
          configMapKeyRef:
            # The ConfigMap containing the value you want to assign to APP_COLOR
            name: webapp-color
            # Specify the key associated with the value
            key: color

Task 17

  1. Create a configmap grafana-ini that containes a file named grafana.ini with the following content:
[server]
  protocol = http
  http_port = 3000
  1. Create a pod grafana that uses grafana/grafana:9.3.1 image.
  2. Mount the configmap to the pod using /etc/grafana/grafana.ini as a mountPath and grafana.ini as a subPath.

Solution 17

Create a configuration file for Grafana:

cat > grafana.ini <<EOF
[server]
  protocol = http
  http_port = 3000
EOF
kubectl create configmap grafana-ini --from-file=grafana.ini -n ckad

kubectl run grafana --image=grafana/grafana:9.3.1 \
  --dry-run=client -o yaml -n ckad > grafana.yaml

Edit the file grafana.yaml and add volumes and volumeMounts sections:

---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: grafana
  name: grafana
  namespace: ckad
spec:
  containers:
  - image: grafana/grafana:9.3.1
    name: grafana
    volumeMounts:
      - name: grafana-config
        mountPath: /etc/grafana/grafana.ini
        subPath: grafana.ini
  volumes:
    - name: grafana-config
      configMap:
        # Provide the name of the ConfigMap containing the files you want
        # to add to the container
        name: grafana-ini

Deploy the pod and verify:

kubectl apply -f grafana.yaml

kubectl exec grafana -n ckad -- cat /etc/grafana/grafana.ini
[server]
  protocol = http
  http_port = 3000

Declarative YAML:

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: grafana-ini
  namespace: ckad
data:
  grafana.ini: |
    [server]
      protocol = http
      http_port = 3000
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: grafana
  name: grafana
  namespace: ckad
spec:
  containers:
  - image: grafana/grafana:9.3.1
    name: grafana
    volumeMounts:
      - name: grafana-config
        mountPath: /etc/grafana/grafana.ini
  volumes:
    - name: grafana-config
      configMap:
        # Provide the name of the ConfigMap containing the files you want
        # to add to the container
        name: grafana-ini

Create and consume Secrets

Docs: https://kubernetes.io/docs/concepts/configuration/secret/#using-secrets-as-environment-variables

Task 18

Configure application to use a Secret.

  1. Create a secret mysql-credentials that has the following key=value pairs:
    • mysql_root_password = Mysql5.7RootPassword
    • mysql_username = dbadmin
    • mysql_password = Mysql5.7UserPassword
  2. Create a pod mysql-pod-secret that uses mysql:5.7 image.
  3. Configure the pod so that the underlying container has the following environment variables set:
    • MYSQL_ROOT_PASSWORD from secret key mysql_root_password
    • MYSQL_USER from secret key mysql_username
    • MYSQL_PASSWORD from secret key mysql_password
  4. Exec a command in the container to show that it has the configured environment variable.

Solution 18

Create a secret:

kubectl create secret generic mysql-credentials \
  --from-literal=mysql_root_password="Mysql5.7RootPassword" \
  --from-literal=mysql_username=dbadmin \
  --from-literal=mysql_password="Mysql5.7UserPassword" \
  -n ckad

kubectl run mysql-pod-secret --image=mysql:5.7 \
  --dry-run=client -o yaml -n ckad > mysql-pod-secret.yaml

Edit the file mysql-pod-secret.yaml and add env section:

---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: mysql-pod-secret
  name: mysql-pod-secret
  namespace: ckad
spec:
  containers:
  - image: mysql:5.7
    name: mysql-pod-secret
    env:
      - name: MYSQL_ROOT_PASSWORD
        valueFrom:
          secretKeyRef:
            name: mysql-credentials
            key: mysql_root_password
      - name: MYSQL_USER
        valueFrom:
          secretKeyRef:
            name: mysql-credentials
            key: mysql_username
      - name: MYSQL_PASSWORD
        valueFrom:
          secretKeyRef:
            name: mysql-credentials
            key: mysql_password

Deploy the pod and validate:

kubectl apply -f mysql-pod-secret.yaml
kubectl exec mysql-pod-secret -n ckad -- env | grep ^MYSQL
MYSQL_MAJOR=5.7
MYSQL_VERSION=5.7.41-1.el7
MYSQL_SHELL_VERSION=8.0.32-1.el7
MYSQL_USER=dbadmin
MYSQL_PASSWORD=Mysql5.7UserPassword
MYSQL_ROOT_PASSWORD=Mysql5.7RootPassword

Declarative YAML:

---
apiVersion: v1
kind: Secret
metadata:
  name: mysql-credentials
  namespace: ckad
data:
  mysql_password: TXlzcWw1LjdVc2VyUGFzc3dvcmQ=
  mysql_root_password: TXlzcWw1LjdSb290UGFzc3dvcmQ=
  mysql_username: ZGJhZG1pbg==
type: Opaque
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: mysql-pod-secret
  name: mysql-pod-secret
  namespace: ckad
spec:
  containers:
  - image: mysql:5.7
    name: mysql-pod-secret
    env:
      - name: MYSQL_ROOT_PASSWORD
        valueFrom:
          secretKeyRef:
            name: mysql-credentials
            key: mysql_root_password
      - name: MYSQL_USER
        valueFrom:
          secretKeyRef:
            name: mysql-credentials
            key: mysql_username
      - name: MYSQL_PASSWORD
        valueFrom:
          secretKeyRef:
            name: mysql-credentials
            key: mysql_password

Understand ServiceAccounts

Docs:

Task 19

  1. Create a new service account pod-sa.
  2. Create a cluster role pod-clusterrole that grants permissions get,list,watch to resources pods,nodes to API group metrics.k8s.io.
  3. Grant the service account access to the cluster by creating a cluster role binding pod-role-binding.
  4. Create a pod called pod-use-sa that uses the service account pod-sa and image nginx:1.21.

Solution 19

Create a service account:

kubectl create sa pod-sa -n ckad

Create a cluser role:

kubectl create clusterrole pod-clusterrole \
  --verb=get,list,watch --resource=pods,nodes \
  --dry-run=client -o yaml | sed 's/- ""/- metrics.k8s.io/g' | kubectl apply -f -

Create a cluster role binding:

kubectl create clusterrolebinding pod-role-binding \
  --clusterrole=pod-clusterrole \
  --serviceaccount=ckad:pod-sa

Create a pod definition file:

kubeclt run pod-use-sa --image=nginx:1.21 \
  --dry-run=client -o yaml -n ckad > pod-use-sa.yaml

Edit the file pod-use-sa.yaml and add serviceAccount section:

---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: pod-use-sa
  name: pod-use-sa
  namespace: ckad
spec:
  serviceAccount: pod-sa
  serviceAccountName: pod-sa
  containers:
  - image: nginx:1.21
    name: pod-use-sa

Deploy the pod:

kubectl apply -f pod-use-sa.yaml

Verify:

kubectl describe po pod-use-sa -n ckad | grep Service
Service Account:  pod-sa

Declarative YAML:

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: pod-sa
  namespace: ckad
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: pod-clusterrole
rules:
- apiGroups:
  - metrics.k8s.io
  resources:
  - pods
  - nodes
  verbs:
  - get
  - list
  - watch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: pod-role-binding
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: pod-clusterrole
subjects:
- kind: ServiceAccount
  name: pod-sa
  namespace: ckad
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: pod-use-sa
  name: pod-use-sa
  namespace: ckad
spec:
  serviceAccount: pod-sa
  serviceAccountName: pod-sa
  containers:
  - image: nginx:1.21
    name: pod-use-sa

Understand SecurityContexts

Docs: https://kubernetes.io/docs/tasks/configure-pod-container/security-context/

Task 20

  1. Create a new pod called unprivileged that uses image busybox:1.35 and runs command sleep 1800.
  2. Set allowPrivilegeEscalation: false and privileged: false for the security context on container level.
  3. The pod should run as UID 1111. The container should run as UID 2222.
  4. Add SYS_TIME capabilities to the container.

Solution 20

Create a pod template:

kubectl run unprivileged --image=busybox:1.35 \
  --dry-run=client -o yaml -n ckad -- sleep 1800 > unprivileged.yaml

Edit the file unprivileged.yaml and add securityContext section.

Note that Linux capabilities can be added only at container level security-context, not at the pod level.

---
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: unprivileged
  name: unprivileged
  namespace: ckad
spec:
  securityContext:
    runAsUser: 1111
  containers:
  - args:
    - sleep
    - "1800"
    image: busybox:1.35
    name: unprivileged
    securityContext:
      allowPrivilegeEscalation: false
      runAsUser: 2222
      capabilities:
        add: ["SYS_TIME"]

Deploy the pod:

kubectl apply -f unprivileged.yaml

Services and Networking

Unless stated otherwise, all Kubernetes resources should be created in the ckad namespace.

Demonstrate basic understanding of NetworkPolicies

Docs: https://kubernetes.io/docs/concepts/services-networking/network-policies/

Task 21

  1. Create a pod httpd-netpol-blue that uses image lisenet/httpd-pii-demo:0.2 and has a label of app=blue.
  2. Create a pod httpd-netpol-green that uses image lisenet/httpd-pii-demo:0.3 and has a label of app=green.
  3. Create a pod curl-netpol that uses image curlimages/curl:7.87.0 and has a label of app=admin. The pod should run the following command sleep 1800.
  4. Create a NetworkPolicy called netpol-blue-green.
  5. The policy should allow the busybox pod only to:
    • connect to httpd-netpol-blue pods on port 80.
  6. Use the app label of pods in your policy.

After implementation, connections from busybox pod to httpd-netpol-green pod on port 80 should no longer work.

Solution 21

Create pods:

kubectl run httpd-netpol-blue --image="lisenet/httpd-pii-demo:0.2" --labels=app=blue -n ckad
kubectl run httpd-netpol-green --image="lisenet/httpd-pii-demo:0.3" --labels=app=green -n ckad
kubectl run curl-netpol --image="curlimages/curl:7.87.0" --labels=app=admin -n ckad -- sleep 1800

Get IP addresses of pods and test web access.

kubectl get po -o wide -n cka | awk '{ print $1" "$6 }'
NAME IP
curl-netpol 192.168.135.204
httpd-netpol-blue 192.168.137.36
httpd-netpol-green 192.168.137.40

kubectl -n cka exec curl-netpol -- curl -sI http://192.168.137.36
HTTP/1.1 200 OK
Date: Tue, 21 Feb 2023 01:05:37 GMT
Server: Apache/2.4.48 (Debian)
X-Powered-By: PHP/7.3.30
Content-Type: text/html; charset=UTF-8

kubectl -n cka exec curl-netpol -- curl -sI http://192.168.137.40
HTTP/1.1 200 OK
Date: Tue, 21 Feb 2023 01:05:37 GMT
Server: Apache/2.4.48 (Debian)
X-Powered-By: PHP/7.3.30
Content-Type: text/html; charset=UTF-8

Create a file netpol-blue-green.yaml with the following content:

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: netpol-blue-green
  namespace: ckad
spec:
  podSelector:
    matchLabels:
      app: admin
  policyTypes:
    - Egress # policy is only about Egress
  egress:
    - to: # first condition "to"
      - podSelector:
          matchLabels:
            app: blue
      ports: # second condition "port"
      - protocol: TCP
        port: 80

Create the network policy and verify:

kubectl apply -f netpol-blue-green.yaml

kubectl get networkpolicy -n ckad
NAME                POD-SELECTOR   AGE
netpol-blue-green   app=admin      29s

Test web access again:

kubectl -n cka exec curl-netpol -- curl -sI --max-time 5 http://192.168.137.36
HTTP/1.1 200 OK
Date: Tue, 21 Feb 2023 01:05:37 GMT
Server: Apache/2.4.48 (Debian)
X-Powered-By: PHP/7.3.30
Content-Type: text/html; charset=UTF-8

kubectl -n cka exec curl-netpol -- curl -sI --max-time 5 http://192.168.137.40
command terminated with exit code 28

Declarative YAML:

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: netpol-blue-green
  namespace: ckad
spec:
  podSelector:
    matchLabels:
      app: admin
  policyTypes:
    - Egress
  egress:
    - to:
      - podSelector:
          matchLabels:
            app: blue
      ports:
      - protocol: TCP
        port: 80
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: blue
  name: httpd-netpol-blue
  namespace: ckad
spec:
  containers:
  - image: lisenet/httpd-pii-demo:0.2
    name: httpd-netpol-blue
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: green
  name: httpd-netpol-green
  namespace: ckad
spec:
  containers:
  - image: lisenet/httpd-pii-demo:0.3
    name: httpd-netpol-green
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: admin
  name: curl-netpol
  namespace: ckad
spec:
  containers:
  - args:
    - "sleep"
    - "1800"
    image: curlimages/curl:7.87.0
    name: curl-netpol

Provide and troubleshoot access to applications via services

Docs: https://kubernetes.io/docs/concepts/services-networking/service/

Task 22

  1. A deployment YAML file for a troublesome-app application is provided below. Use it to deploy a service that exposes a pod on NodePort: 30080.
  2. Do not change the pod definition. Assume that the pod definition is correct.
  3. Troubleshoot access problem and fix it so that the application would be available via a NodePort service.
  4. Test access with curl -s http://127.0.0.1:30080.
# troublesome-app.yaml
---
apiVersion: v1
kind: Pod
metadata:
  annotations:
    cluster-autoscaler.kubernetes.io/safe-to-evict: "true"
  labels:
    app: web
    tier: frontend
  name: troublesome-app
  namespace: ckad
spec:
  containers:
  - name: troublesome-pod
    image: kodekloud/webapp-color
    imagePullPolicy: IfNotPresent
    env:
    - name: APP_COLOR
      value: red
    ports:
    - containerPort: 8080
    resources:
      limits:
        cpu: 50m
  dnsPolicy: ClusterFirst
  restartPolicy: Always
---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: troublesome-app-ingress-netpol
  namespace: ckad
spec:
  podSelector:
    matchLabels:
      tier: frontend
  ingress:
  - {}
  policyTypes:
  - Ingress
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: wepapp-color
  name: troublesome-app
  namespace: ckad
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
    nodePort: 30080
  type: NodePort
  selector:
    app: wepapp-color

Use Ingress rules to expose applications

Docs:

Note: you must have an Ingress controller to satisfy an Ingress. Only creating an Ingress resource has no effect.

Task 23

  1. Create a deployment object httpd-pii-demo-blue containing a single lisenet/httpd-pii-demo:0.2 container and expose its port 80 through a type LoadBalancer service.
  2. Create a deployment object httpd-pii-demo-green containing a single lisenet/httpd-pii-demo:0.3 container and expose its port 80 through a type LoadBalancer service.
  3. Deploy ingress-nginx controller.
  4. Create the ingress resource ingress-blue-green to make the applications available at /blue and /green on the Ingress service.

Solution 23

Create and expose deployments:

kubectl create deploy httpd-pii-demo-blue --image="lisenet/httpd-pii-demo:0.2" -n ckad
kubectl expose deploy/httpd-pii-demo-blue --port=80 --target-port=80 --type=LoadBalancer -n ckad

kubectl create deploy httpd-pii-demo-green --image="lisenet/httpd-pii-demo:0.3" -n ckad
kubectl expose deploy/httpd-pii-demo-green --port=80 --target-port=80 --type=LoadBalancer -n ckad

Deploy an ingress resource:

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.6.4/deploy/static/provider/cloud/deploy.yaml

Verify:

kubectl get svc -n ingress-nginx
NAME                                 TYPE           CLUSTER-IP       EXTERNAL-IP   PORT(S)                      AGE
ingress-nginx-controller             LoadBalancer   10.110.55.43     <pending>     80:30740/TCP,443:32596/TCP   49s
ingress-nginx-controller-admission   ClusterIP      10.106.169.189   <none>        443/TCP                      49s

Create a manifest file ingress-blue-green.yaml for an ingress resource:

---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-blue-green
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
  namespace: ckad
spec:
  ingressClassName: nginx
  rules:
  - http:
      paths:
      - path: /blue
        pathType: Prefix
        backend:
          service:
            name: httpd-pii-demo-blue
            port:
              number: 80
      - path: /green
        pathType: Prefix
        backend:
          service:
            name: httpd-pii-demo-green
            port:
              number: 80

Deploy ingress resource and verify:

kubectl apply -f ingress-blue-green.yaml
kubectl describe ingress/ingress-blue-green -n ckad
Name:             ingress-blue-green
Labels:           <none>
Namespace:        ckad
Address:          
Ingress Class:    nginx
Default backend:  <default>
Rules:
  Host        Path  Backends
  ----        ----  --------
  *           
              /blue    httpd-pii-demo-blue:80 (10.244.1.50:80)
              /green   httpd-pii-demo-green:80 (10.244.1.51:80)
Annotations:  nginx.ingress.kubernetes.io/rewrite-target: /
Events:
  Type    Reason  Age   From                      Message
  ----    ------  ----  ----                      -------
  Normal  Sync    13s   nginx-ingress-controller  Scheduled for sync