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
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Fix the nginx pod. The YAML file is given.
controlplane ~ ➜ k get po NAME READY STATUS RESTARTS AGE nginx 0/1 Pending 0 3m18s## nginx.yaml apiVersion: v1 kind: Pod metadata: name: nginx spec: containers: - image: nginx name: nginx
Answer
Check the details of all pods, including pods in the kube-system namespace. Here we can see that there is no scheduler pod. Without this scheduler pod, all other pods in the default namespace will remain in pending state forever.
controlplane ~ ➜ k get po NAME READY STATUS RESTARTS AGE nginx 0/1 Pending 0 25s controlplane ~ ➜ controlplane ~ ➜ k get po -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx 0/1 Pending 0 31s <none> <none> <none> <none> controlplane ~ ➜ k get po -A -o wide NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES default nginx 0/1 Pending 0 38s <none> <none> <none> <none> kube-flannel kube-flannel-ds-hn474 1/1 Running 0 8m23s 192.38.195.8 node01 <none> <none> kube-flannel kube-flannel-ds-zvkr9 1/1 Running 0 8m38s 192.38.195.6 controlplane <none> <none> kube-system coredns-5d78c9869d-5nt4f 1/1 Running 0 8m37s 10.244.0.2 controlplane <none> <none> kube-system coredns-5d78c9869d-8wwkp 1/1 Running 0 8m37s 10.244.0.3 controlplane <none> <none> kube-system etcd-controlplane 1/1 Running 0 8m52s 192.38.195.6 controlplane <none> <none> kube-system kube-apiserver-controlplane 1/1 Running 0 8m53s 192.38.195.6 controlplane <none> <none> kube-system kube-controller-manager-controlplane 1/1 Running 0 8m52s 192.38.195.6 controlplane <none> <none> kube-system kube-proxy-9qxp8 1/1 Running 0 8m23s 192.38.195.8 node01 <none> <none> kube-system kube-proxy-dptpt 1/1 Running 0 8m38s 192.38.195.6 controlplane <none> <none>
Delete pod first and manually schedule on a node.
controlplane ~ ➜ k get no NAME STATUS ROLES AGE VERSION controlplane Ready control-plane 8m15s v1.27.0 node01 Ready <none> 7m34s v1.27.0 controlplane ~ ➜ k delete po nginx pod "nginx" deleted controlplane ~ ➜ k get po No resources found in default namespace.
To manually schedule, modify the YAML file and apply.
## nginx.yaml apiVersion: v1 kind: Pod metadata: name: nginx spec: nodeName=node01 containers: - image: nginx name: nginx
controlplane ~ ➜ k apply -f nginx.yaml pod/nginx created controlplane ~ ➜ k get po NAME READY STATUS RESTARTS AGE nginx 1/1 Running 0 8s
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We have deployed a number of PODs. They are labelled with tier, env and bu. How many PODs exist in the dev environment (env)?
controlplane ~ ➜ k get po NAME READY STATUS RESTARTS AGE app-1-whhgk 1/1 Running 0 107s db-1-9qjgg 1/1 Running 0 106s db-1-jhqfb 1/1 Running 0 107s app-1-sk7dg 1/1 Running 0 107s app-1-rtm89 1/1 Running 0 107s auth 1/1 Running 0 106s db-1-5z6hx 1/1 Running 0 106s app-1-zzxdf 1/1 Running 0 106s app-2-wdhp9 1/1 Running 0 107s db-1-8nlqw 1/1 Running 0 106s db-2-ds4b8 1/1 Running 0 106sAnswer
controlplane ~ ➜ k get po --show-labels=true NAME READY STATUS RESTARTS AGE LABELS app-1-whhgk 1/1 Running 0 111s bu=finance,env=dev,tier=frontend db-1-9qjgg 1/1 Running 0 110s env=dev,tier=db db-1-jhqfb 1/1 Running 0 111s env=dev,tier=db app-1-sk7dg 1/1 Running 0 111s bu=finance,env=dev,tier=frontend app-1-rtm89 1/1 Running 0 111s bu=finance,env=dev,tier=frontend auth 1/1 Running 0 110s bu=finance,env=prod db-1-5z6hx 1/1 Running 0 110s env=dev,tier=db app-1-zzxdf 1/1 Running 0 110s bu=finance,env=prod,tier=frontend app-2-wdhp9 1/1 Running 0 111s env=prod,tier=frontend db-1-8nlqw 1/1 Running 0 110s env=dev,tier=db db-2-ds4b8 1/1 Running 0 110s bu=finance,env=prod,tier=db controlplane ~ ➜ k get po --show-labels=true | grep "env=dev" app-1-whhgk 1/1 Running 0 2m bu=finance,env=dev,tier=frontend db-1-9qjgg 1/1 Running 0 119s env=dev,tier=db db-1-jhqfb 1/1 Running 0 2m env=dev,tier=db app-1-sk7dg 1/1 Running 0 2m bu=finance,env=dev,tier=frontend app-1-rtm89 1/1 Running 0 2m bu=finance,env=dev,tier=frontend db-1-5z6hx 1/1 Running 0 119s env=dev,tier=db db-1-8nlqw 1/1 Running 0 119s env=dev,tier=db
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How many PODs are in the finance business unit (bu)?
Answer
controlplane ~ ➜ k get po --show-labels=true | grep "bu=finance" app-1-whhgk 1/1 Running 0 2m43s bu=finance,env=dev,tier=frontend app-1-sk7dg 1/1 Running 0 2m43s bu=finance,env=dev,tier=frontend app-1-rtm89 1/1 Running 0 2m43s bu=finance,env=dev,tier=frontend auth 1/1 Running 0 2m42s bu=finance,env=prod app-1-zzxdf 1/1 Running 0 2m42s bu=finance,env=prod,tier=frontend db-2-ds4b8 1/1 Running 0 2m42s bu=finance,env=prod,tier=db
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How many objects are in the prod environment including PODs, ReplicaSets and any other objects?
Answer
controlplane ~ ➜ k get all --show-labels=true | grep "env=prod" pod/auth 1/1 Running 0 4m7s bu=finance,env=prod pod/app-1-zzxdf 1/1 Running 0 4m7s bu=finance,env=prod,tier=frontend pod/app-2-wdhp9 1/1 Running 0 4m8s env=prod,tier=frontend pod/db-2-ds4b8 1/1 Running 0 4m7s bu=finance,env=prod,tier=db service/app-1 ClusterIP 10.43.234.201 <none> 3306/TCP 4m7s bu=finance,env=prod replicaset.apps/app-2 1 1 1 4m8s env=prod replicaset.apps/db-2 1 1 1 4m7s env=prod
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Identify the POD which is part of the prod environment, the finance BU and of frontend tier?
Answer
controlplane ~ ➜ k get po -l bu=finance,env=prod,tier=frontend NAME READY STATUS RESTARTS AGE app-1-zzxdf 1/1 Running 0 6m43s
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How many labels does node01 have?
Answer
controlplane ~ ➜ k describe no node01 | grep Labels -A 10 Labels: beta.kubernetes.io/arch=amd64 beta.kubernetes.io/os=linux kubernetes.io/arch=amd64 kubernetes.io/hostname=node01 kubernetes.io/os=linux Annotations: flannel.alpha.coreos.com/backend-data: {"VNI":1,"VtepMAC":"96:49:b7:34:27:94"} flannel.alpha.coreos.com/backend-type: vxlan flannel.alpha.coreos.com/kube-subnet-manager: true flannel.alpha.coreos.com/public-ip: 192.10.195.3 kubeadm.alpha.kubernetes.io/cri-socket: unix:///var/run/containerd/containerd.sock node.alpha.kubernetes.io/ttl: 0
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Apply a label color=blue to node node01
Answer
controlplane ~ ➜ k label no node01 color=blue node/node01 labeled controlplane ~ ➜ k describe no node01 | grep -A 10 Labels Labels: beta.kubernetes.io/arch=amd64 beta.kubernetes.io/os=linux color=blue kubernetes.io/arch=amd64 kubernetes.io/hostname=node01 kubernetes.io/os=linux
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Do any taints exist on node01 node?
controlplane ~ ➜ k get no NAME STATUS ROLES AGE VERSION controlplane Ready control-plane 21m v1.27.0 node01 Ready <none> 20m v1.27.0
Answer
controlplane ~ ➜ k describe no node01 | grep Taints Taints: <none>
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Create a taint on node01 with:
- key of spray
- value of mortein
- effect of NoSchedule
Answer
controlplane ~ ➜ k taint no node01 spray=mortein:NoSchedule node/node01 tainted controlplane ~ ➜ k describe no node01 | grep Taints Taints: spray=mortein:NoSchedule
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Create another pod named bee with the nginx image, which has a toleration set to the taint mortein.
Answer
Generate the YAML file first.
controlplane ~ ➜ export dr="--dry-run=client" controlplane ~ ➜ k run bee --image=nginx $dr pod/bee created (dry run) controlplane ~ ➜ k run bee --image=nginx $dr -o yaml > bee.yml controlplane ~ ➜ ls bee.yml
Search on the k8s docs the paramters for tolerations and add it to the YAML file. Apply afterwards.
## bee.yml apiVersion: v1 kind: Pod metadata: creationTimestamp: null labels: run: bee name: bee spec: containers: - image: nginx name: bee resources: {} dnsPolicy: ClusterFirst restartPolicy: Always tolerations: - key: "spray" value: "mortein" effect: "NoSchedule" status: {}
controlplane ~ ➜ k apply -f bee.yml pod/bee created controlplane ~ ➜ k get po NAME READY STATUS RESTARTS AGE bee 1/1 Running 0 9s mosquito 0/1 Pending 0 8m48s
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Remove the taint on controlplane.
controlplane ~ ➜ k get no NAME STATUS ROLES AGE VERSION controlplane Ready control-plane 35m v1.27.0 node01 Ready <none> 34m v1.27.0
Answer
controlplane ~ ➜ k describe no controlplane | grep Taint Taints: node-role.kubernetes.io/control-plane:NoSchedule controlplane ~ ✖ k taint no controlplane node-role.kubernetes.io/control-plane:NoSchedule- node/controlplane untainted controlplane ~ ➜ k describe no controlplane | grep Taint Taints: <none>
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Set Node Affinity to the deployment to place the pods on node01 only.
Answer
Get the YAML file and modify by adding the parameters for the node affinity. See K8s docs for format.
controlplane ~ ➜ k get deployments.apps blue -o yaml > blue.yml
## blue.yml apiVersion: apps/v1 kind: Deployment metadata: creationTimestamp: null labels: app: blue name: blue spec: replicas: 3 selector: matchLabels: app: blue strategy: {} template: metadata: creationTimestamp: null labels: app: blue spec: containers: - image: nginx name: nginx resources: {} affinity: nodeAffinity: requiredDuringSchedulingIgnoredDuringExecution: nodeSelectorTerms: - matchExpressions: - key: color operator: In values: - blue status: {}controlplane ~ ➜ k apply -f blue.yml deployment.apps/blue created controlplane ~ ➜ k get po -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES blue-f69d4c887-6whqb 1/1 Running 0 10s 10.244.1.6 node01 <none> <none> blue-f69d4c887-j8x27 1/1 Running 0 10s 10.244.1.4 node01 <none> <none> blue-f69d4c887-z8hbl 1/1 Running 0 10s 10.244.1.5 node01 <none> <none>
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Create a new deployment named red with the nginx image and 2 replicas, and ensure it gets placed on the controlplane node only.
Use the label key - node-role.kubernetes.io/control-plane - which is already set on the controlplane node.
Answer
Verify label.
controlplane ~ ➜ k describe nodes controlplane | grep -A 10 Labels Labels: beta.kubernetes.io/arch=amd64 beta.kubernetes.io/os=linux kubernetes.io/arch=amd64 kubernetes.io/hostname=controlplane kubernetes.io/os=linux node-role.kubernetes.io/control-plane= node.kubernetes.io/exclude-from-external-load-balancers= Annotations: flannel.alpha.coreos.com/backend-data: {"VNI":1,"VtepMAC":"ca:c9:cd:c5:51:72"} flannel.alpha.coreos.com/backend-type: vxlan flannel.alpha.coreos.com/kube-subnet-manager: true flannel.alpha.coreos.com/public-ip: 192.12.20.6
Generate the YAML and add the affinity parameter. See K8s docs for format.
controlplane ~ ➜ k create deployment red --image nginx --replicas 2 $do > red.yml
## red.yml apiVersion: apps/v1 kind: Deployment metadata: creationTimestamp: null labels: app: red name: red spec: replicas: 2 selector: matchLabels: app: red strategy: {} template: metadata: creationTimestamp: null labels: app: red spec: containers: - image: nginx name: nginx resources: {} affinity: nodeAffinity: requiredDuringSchedulingIgnoredDuringExecution: nodeSelectorTerms: - matchExpressions: - key: node-role.kubernetes.io/control-plane operator: Existscontrolplane ~ ➜ k apply -f red.yml deployment.apps/red created controlplane ~ ➜ k get deployments.apps NAME READY UP-TO-DATE AVAILABLE AGE blue 3/3 3 3 10m red 2/2 2 2 13s
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A pod called rabbit is deployed. Identify the CPU requirements set on the Pod.
controlplane ~ ➜ k get po NAME READY STATUS RESTARTS AGE rabbit 0/1 CrashLoopBackOff 4 (31s ago) 118sAnswer
controlplane ~ ➜ k describe po rabbit | grep -A 5 -i requests Requests: cpu: 1
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Another pod called elephant has been deployed in the default namespace. It fails to get to a running state. Inspect this pod and identify the Reason why it is not running.
controlplane ~ ➜ k get po NAME READY STATUS RESTARTS AGE elephant 0/1 CrashLoopBackOff 3 (33s ago) 86sAnswer
The status OOMKilled indicates that it is failing because the pod ran out of memory. Identify the memory limit set on the POD.
controlplane ~ ➜ k describe pod elephant | grep -A 5 State State: Terminated Reason: OOMKilled Exit Code: 1 Started: Fri, 29 Dec 2023 07:25:52 +0000 Finished: Fri, 29 Dec 2023 07:25:52 +0000 Last State: Terminated Reason: OOMKilled Exit Code: 1 Started: Fri, 29 Dec 2023 07:25:01 +0000 Finished: Fri, 29 Dec 2023 07:25:01 +0000 Ready: False
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The elephant pod runs a process that consumes 15Mi of memory. Increase the limit of the elephant pod to 20Mi.
controlplane ~ ➜ k get po NAME READY STATUS RESTARTS AGE elephant 0/1 CrashLoopBackOff 3 (33s ago) 86sAnswer
controlplane ~ ✦ ➜ k get po -o yaml > el.yaml
## el.yaml apiVersion: v1 items: - apiVersion: v1 kind: Pod metadata: creationTimestamp: "2023-12-29T07:24:08Z" name: elephant namespace: default resourceVersion: "952" uid: fe698e64-ca6b-4990-813a-9b63c7cc2b2b spec: containers: - args: - --vm - "1" - --vm-bytes - 15M - --vm-hang - "1" command: - stress image: polinux/stress imagePullPolicy: Always name: mem-stress resources: limits: memory: 20Mi requests: memory: 5Mi
controlplane ~ ✦ ➜ k delete po elephant $now Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely. pod "elephant" force deleted controlplane ~ ✦ ➜ k apply -f el.yaml pod/elephant created controlplane ~ ✦ ✖ k get po NAME READY STATUS RESTARTS AGE elephant 1/1 Running 0 39s
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How many DaemonSets in all namespaces?
Answer
controlplane ~ ➜ k get ds -A NAMESPACE NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE kube-flannel kube-flannel-ds 1 1 1 1 1 <none> 4m31s kube-system kube-proxy 1 1 1 1 1 kubernetes.io/os=linux 4m34s
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What is the image used by the POD deployed by the kube-flannel-ds DaemonSet?
Answer
controlplane ~ ➜ k get ds -A NAMESPACE NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE kube-flannel kube-flannel-ds 1 1 1 1 1 <none> 6m57s kube-system kube-proxy 1 1 1 1 1 kubernetes.io/os=linux 7m controlplane ~ ➜ k describe daemonsets.apps -n kube-flannel kube-flannel-ds | grep Image Image: docker.io/rancher/mirrored-flannelcni-flannel-cni-plugin:v1.1.0 Image: docker.io/rancher/mirrored-flannelcni-flannel:v0.19.2 Image: docker.io/rancher/mirrored-flannelcni-flannel:v0.19.2
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Deploy a DaemonSet for FluentD Logging.
- Name: elasticsearch
- Namespace: kube-system
- Image: registry.k8s.io/fluentd-elasticsearch:1.20
Answer
Copy the FluentD YAML from K8S docs and modify. Apply afterwards.
## fluentd.yml apiVersion: apps/v1 kind: DaemonSet metadata: name: elasticsearch namespace: kube-system labels: k8s-app: fluentd-logging spec: selector: matchLabels: name: fluentd-elasticsearch template: metadata: labels: name: fluentd-elasticsearch spec: tolerations: # these tolerations are to have the daemonset runnable on control plane nodes # remove them if your control plane nodes should not run pods - key: node-role.kubernetes.io/control-plane operator: Exists effect: NoSchedule - key: node-role.kubernetes.io/master operator: Exists effect: NoSchedule containers: - name: fluentd-elasticsearch image: registry.k8s.io/fluentd-elasticsearch:1.20 resources: limits: memory: 200Mi requests: cpu: 100m memory: 200Mi volumeMounts: - name: varlog mountPath: /var/log # it may be desirable to set a high priority class to ensure that a DaemonSet Pod # preempts running Pods # priorityClassName: important terminationGracePeriodSeconds: 30 volumes: - name: varlog hostPath: path: /var/log
controlplane ~ ➜ k apply -f fluentd.yml daemonset.apps/elasticsearch created controlplane ~ ➜ k get ds -A NAMESPACE NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE kube-flannel kube-flannel-ds 1 1 1 1 1 <none> 10m kube-system elasticsearch 1 1 1 1 1 <none> 4s kube-system kube-proxy 1 1 1 1 1 kubernetes.io/os=linux 10m
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How many static pods exist in this cluster in all namespaces?
Answer
controlplane ~ ➜ k get po -A | grep controlplane kube-system etcd-controlplane 1/1 Running 0 6m41s kube-system kube-apiserver-controlplane 1/1 Running 0 6m39s kube-system kube-controller-manager-controlplane 1/1 Running 0 6m39s kube-system kube-scheduler-controlplane 1/1 Running 0 6m41s
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On which nodes are the static pods created currently?
Answer
controlplane ~ ➜ k get po -o wide -A | grep controlplane kube-system etcd-controlplane 1/1 Running 0 8m9s 192.13.225.9 controlplane <none> <none> kube-system kube-apiserver-controlplane 1/1 Running 0 8m7s 192.13.225.9 controlplane <none> <none> kube-system kube-controller-manager-controlplane 1/1 Running 0 8m7s 192.13.225.9 controlplane <none> <none> kube-system kube-scheduler-controlplane 1/1 Running 0 8m9s 192.13.225.9 controlplane <none> <none>
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What is the path of the directory holding the static pod definition files?
Answer
First idenity the kubelet config file (--config):
controlplane ~ ➜ ps -aux | grep /usr/bin/kubelet root 4685 0.0 0.0 3775504 101080 ? Ssl 02:35 0:10 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --container-runtime-endpoint=unix:///var/run/containerd/containerd.sock --pod-infra-container-image=registry.k8s.io/pause:3.9 root 9476 0.0 0.0 6748 2540 pts/0 S+ 02:46 0:00 grep --color=auto /usr/bin/kubelet
Next, lookup the value assigned for staticPodPath:
controlplane ~ ➜ grep static /var/lib/kubelet/config.yaml staticPodPath: /etc/kubernetes/manifests
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How many pod definition files are present in the manifests directory?
Answer
controlplane ~ ➜ ls -la /etc/kubernetes/manifests/ total 28 drwxr-xr-x 1 root root 4096 Dec 29 02:35 . drwxr-xr-x 1 root root 4096 Dec 29 02:35 .. -rw------- 1 root root 2405 Dec 29 02:35 etcd.yaml -rw------- 1 root root 3882 Dec 29 02:35 kube-apiserver.yaml -rw------- 1 root root 3393 Dec 29 02:35 kube-controller-manager.yaml -rw------- 1 root root 1463 Dec 29 02:35 kube-scheduler.yaml
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What is the docker image used to deploy the kube-api server as a static pod?
Answer
controlplane ~ ➜ ls -la /etc/kubernetes/manifests/ total 28 drwxr-xr-x 1 root root 4096 Dec 29 02:35 . drwxr-xr-x 1 root root 4096 Dec 29 02:35 .. -rw------- 1 root root 2405 Dec 29 02:35 etcd.yaml -rw------- 1 root root 3882 Dec 29 02:35 kube-apiserver.yaml -rw------- 1 root root 3393 Dec 29 02:35 kube-controller-manager.yaml -rw------- 1 root root 1463 Dec 29 02:35 kube-scheduler.yaml controlplane ~ ➜ grep image /etc/kubernetes/manifests/kube-apiserver.yaml image: registry.k8s.io/kube-apiserver:v1.27.0 imagePullPolicy: IfNotPresent
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Create a static pod named static-busybox that uses the busybox image and the command sleep 1000
Answer
controlplane ~ ➜ k run po static-busy-box --image busybox $do > bb.yml
Note that since it's a static pod, it needs to be created in the /etc/kubernetes/manifests directory.
controlplane ~ ➜ cd /etc/kubernetes/manifests/ controlplane /etc/kubernetes/manifests ➜ controlplane /etc/kubernetes/manifests ➜ k run static-busybox --image busybox $do > /etc/kubernetes/manifests/static-busybox.yml controlplane /etc/kubernetes/manifests ➜ ls -la /etc/kubernetes/manifests/ total 36 drwxr-xr-x 1 root root 4096 Dec 29 02:56 . drwxr-xr-x 1 root root 4096 Dec 29 02:35 .. -rw------- 1 root root 2405 Dec 29 02:35 etcd.yaml -rw------- 1 root root 3882 Dec 29 02:35 kube-apiserver.yaml -rw------- 1 root root 3393 Dec 29 02:35 kube-controller-manager.yaml -rw------- 1 root root 1463 Dec 29 02:35 kube-scheduler.yaml -rw-r--r-- 1 root root 256 Dec 29 02:56 static-busybox.yml
Add the command parameter and apply afterwards.
## /etc/kubernetes/manifests/static-busybox.yml apiVersion: v1 kind: Pod metadata: creationTimestamp: null labels: run: static-busybox name: static-busybox spec: containers: - command: - sleep - "1000" image: busybox name: static-busybox resources: {} dnsPolicy: ClusterFirst restartPolicy: Never status: {}
controlplane /etc/kubernetes/manifests ➜ k get po NAME READY STATUS RESTARTS AGE static-busybox-controlplane 1/1 Running 0 2s
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We just created a new static pod named static-greenbox. Prevent this pod from restarting when it is deleted.
Answer
controlplane /etc/kubernetes/manifests ✦2 ➜ k get po NAME READY STATUS RESTARTS AGE static-busybox-controlplane 1/1 Running 0 27s static-greenbox-node01 1/1 Running 0 14s controlplane /etc/kubernetes/manifests ✦2 ➜ k get po -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES static-busybox-controlplane 1/1 Running 0 32s 10.244.0.5 controlplane <none> <none> static-greenbox-node01 1/1 Running 0 19s 10.244.1.2 node01 <none> <none>
controlplane /etc/kubernetes/manifests ✦2 ✖ k delete po static-greenbox-node01 $now Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely. pod "static-greenbox-node01" force deleted controlplane /etc/kubernetes/manifests ✦2 ➜ k get po -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES static-busybox-controlplane 1/1 Running 0 81s 10.244.0.5 controlplane <none> <none>
SSH to node01 and find the config file (--config).
controlplane /etc/kubernetes/manifests ✦2 ➜ ssh node01 Warning: Permanently added the ECDSA host key for IP address '192.14.237.3' to the list of known hosts. root@node01 ~ ➜ ps -aux | grep /usr/bin/kubelet root 4435 0.0 0.0 3330296 94296 ? Ssl 03:19 0:01 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --container-runtime-endpoint=unix:///var/run/containerd/containerd.sock --pod-infra-container-image=registry.k8s.io/pause:3.9 root 5398 0.0 0.0 5200 720 pts/0 S+ 03:22 0:00 grep /usr/bin/kubelet root@node01 ~ ➜ grep static /var/lib/kubelet/config.yaml staticPodPath: /etc/just-to-mess-with-you root@node01 ~ ➜ ls -la /etc/just-to-mess-with-you/ total 16 drwxr-xr-x 2 root root 4096 Dec 29 03:20 . drwxr-xr-x 1 root root 4096 Dec 29 03:19 .. -rw-r--r-- 1 root root 301 Dec 29 03:20 greenbox.yaml root@node01 ~ ➜ sudo rm /etc/just-to-mess-with-you/greenbox.yaml
Return to the controlplane and verify that the greenbox pod does not restart anymore.
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What is the image used in the scheduler pod?
Answer
controlplane ~ ➜ k get po -A NAMESPACE NAME READY STATUS RESTARTS AGE kube-flannel kube-flannel-ds-bcc4q 1/1 Running 0 4m13s kube-system coredns-5d78c9869d-6jbzh 1/1 Running 0 4m12s kube-system coredns-5d78c9869d-g5kln 1/1 Running 0 4m12s kube-system etcd-controlplane 1/1 Running 0 4m24s kube-system kube-apiserver-controlplane 1/1 Running 0 4m24s kube-system kube-controller-manager-controlplane 1/1 Running 0 4m24s kube-system kube-proxy-cdzqm 1/1 Running 0 4m13s kube-system kube-scheduler-controlplane 1/1 Running 0 4m24s controlplane ~ ➜ k describe po -n kube-system kube-scheduler-controlplane | grep image controlplane ~ ✖ k describe po -n kube-system kube-scheduler-controlplane | grep -i image Image: registry.k8s.io/kube-scheduler:v1.27.0 Image ID: registry.k8s.io/kube-scheduler@sha256:939d0c6675c373639f53f05d61b5035172f95afb47ecffee6baf4e3d70543b66
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Create a configmap that the new scheduler will employ using the concept of ConfigMap as a volume. We have already given a configMap definition file called my-scheduler-configmap.yaml at /root/ path that will create a configmap with name my-scheduler-config using the content of file /root/my-scheduler-config.yaml.
Answer
controlplane ~ ➜ ls -l total 16 -rw-r--r-- 1 root root 341 Dec 29 03:27 my-scheduler-configmap.yaml -rw-rw-rw- 1 root root 160 Dec 13 05:39 my-scheduler-config.yaml -rw-rw-rw- 1 root root 893 Dec 13 05:39 my-scheduler.yaml -rw-rw-rw- 1 root root 105 Dec 13 05:39 nginx-pod.yaml controlplane ~ ➜ k apply -f my-scheduler-configmap.yaml configmap/my-scheduler-config created controlplane ~ ➜ k get cm NAME DATA AGE kube-root-ca.crt 1 7m58s controlplane ~ ➜ k get cm -A NAMESPACE NAME DATA AGE default kube-root-ca.crt 1 8m1s kube-flannel kube-flannel-cfg 2 8m11s kube-flannel kube-root-ca.crt 1 8m1s kube-node-lease kube-root-ca.crt 1 8m1s kube-public cluster-info 2 8m15s kube-public kube-root-ca.crt 1 8m1s kube-system coredns 1 8m13s kube-system extension-apiserver-authentication 6 8m18s kube-system kube-apiserver-legacy-service-account-token-tracking 1 8m18s kube-system kube-proxy 2 8m13s kube-system kube-root-ca.crt 1 8m1s kube-system kubeadm-config 1 8m16s kube-system kubelet-config 1 8m16s kube-system my-scheduler-config 1 6s
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Deploy an additional scheduler to the cluster following the given specification. Use the manifest file provided at /root/my-scheduler.yaml. Use the same image as used by the default kubernetes scheduler.
Answer
controlplane ~ ➜ ls -l total 16 -rw-r--r-- 1 root root 341 Dec 29 03:27 my-scheduler-configmap.yaml -rw-rw-rw- 1 root root 160 Dec 13 05:39 my-scheduler-config.yaml -rw-rw-rw- 1 root root 893 Dec 13 05:39 my-scheduler.yaml -rw-rw-rw- 1 root root 105 Dec 13 05:39 nginx-pod.yaml controlplane ~ ➜ k get po -n kube-system NAME READY STATUS RESTARTS AGE coredns-5d78c9869d-6jbzh 1/1 Running 0 9m45s coredns-5d78c9869d-g5kln 1/1 Running 0 9m45s etcd-controlplane 1/1 Running 0 9m57s kube-apiserver-controlplane 1/1 Running 0 9m57s kube-controller-manager-controlplane 1/1 Running 0 9m57s kube-proxy-cdzqm 1/1 Running 0 9m46s kube-scheduler-controlplane 1/1 Running 0 9m57s controlplane ~ ✖ k describe po -n kube-system kube-scheduler-controlplane | grep -i image Image: registry.k8s.io/kube-scheduler:v1.27.0 Image ID: registry.k8s.io/kube-scheduler@sha256:939d0c6675c373639f53f05d61b5035172f95afb47ecffee6baf4e3d70543b66
## my-scheduler.yaml apiVersion: v1 kind: Pod metadata: labels: run: my-scheduler name: my-scheduler namespace: kube-system spec: serviceAccountName: my-scheduler containers: - image: registry.k8s.io/kube-scheduler:v1.27.0 command: - /usr/local/bin/kube-scheduler - --config=/etc/kubernetes/my-scheduler/my-scheduler-config.yamlcontrolplane ~ ➜ k apply -f my-scheduler.yaml pod/my-scheduler created controlplane ~ ➜ k get po -n kube-system NAME READY STATUS RESTARTS AGE coredns-5d78c9869d-6jbzh 1/1 Running 0 12m coredns-5d78c9869d-g5kln 1/1 Running 0 12m etcd-controlplane 1/1 Running 0 12m kube-apiserver-controlplane 1/1 Running 0 12m kube-controller-manager-controlplane 1/1 Running 0 12m kube-proxy-cdzqm 1/1 Running 0 12m kube-scheduler-controlplane 1/1 Running 0 12m my-scheduler 1/1 Running 0 7s
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Modify the nginx-pod.yml file POD to create a POD with the new custom scheduler.
Answer
controlplane ~ ✦ ➜ k get po -A NAMESPACE NAME READY STATUS RESTARTS AGE kube-flannel kube-flannel-ds-bcc4q 1/1 Running 0 14m kube-system coredns-5d78c9869d-6jbzh 1/1 Running 0 14m kube-system coredns-5d78c9869d-g5kln 1/1 Running 0 14m kube-system etcd-controlplane 1/1 Running 0 14m kube-system kube-apiserver-controlplane 1/1 Running 0 14m kube-system kube-controller-manager-controlplane 1/1 Running 0 14m kube-system kube-proxy-cdzqm 1/1 Running 0 14m kube-system kube-scheduler-controlplane 1/1 Running 0 14m kube-system my-scheduler 1/1 Running 0 2m43sAdd the new custom scheduler.
## nginx-pod.yaml apiVersion: v1 kind: Pod metadata: name: nginx spec: schedulerName: my-scheduler containers: - image: nginx name: nginx
controlplane ~ ✦ ➜ k apply -f nginx-pod.yaml pod/nginx created controlplane ~ ✦ ➜ k get po -A NAMESPACE NAME READY STATUS RESTARTS AGE default nginx 1/1 Running 0 3s kube-flannel kube-flannel-ds-bcc4q 1/1 Running 0 17m kube-system coredns-5d78c9869d-6jbzh 1/1 Running 0 17m kube-system coredns-5d78c9869d-g5kln 1/1 Running 0 17m kube-system etcd-controlplane 1/1 Running 0 17m kube-system kube-apiserver-controlplane 1/1 Running 0 17m kube-system kube-controller-manager-controlplane 1/1 Running 0 17m kube-system kube-proxy-cdzqm 1/1 Running 0 17m kube-system kube-scheduler-controlplane 1/1 Running 0 17m kube-system my-scheduler 1/1 Running 0 5m47s