目錄

• • Question 1 | Contexts
  • Question 2 | Schedule Pod on Controlplane Node
  • Question 3 | Scale down StatefulSet
  • Question 4 | Pod Ready if Service is reachable
  • Question 5 | Kubectl sorting
  • Question 6 | Storage, PV, PVC, Pod volume
  • Question 7 | Node and Pod Resource Usage
  • Question 8 | Get Controlplane Information
  • Question 9 | Kill Scheduler, Manual Scheduling
  • Question 11 | DaemonSet on all Nodes
  • Question 12 | Deployment on all Nodes
  • Question 13 | Multi Containers and Pod shared Volume
  • Question 14 | Find out Cluster Information
  • Question 15 | Cluster Event Logging
  • Question 16 | Namespaces and Api Resources
  • Question 17 | Find Container of Pod and check info
  • Question 18 | Fix Kubelet
  • Question 19 | Create Secret and mount into Pod
  • Question 20 | Update Kubernetes Version and join cluster
  • Question 21 | Create a Static Pod and Service
  • Question 22 | Check how long certificates are valid
  • Question 23 | Kubelet client/server cert info
  • Question 24 | NetworkPolicy
  • Question 25 | Etcd Snapshot Save and Restore
  • Extra Question 1 | Find Pods first to be terminated
  • Extra Question 2 | Curl Manually Contact API
  • Preview Question 1
  • Preview Question 2
  • Preview Question 3
  • CKA Tips Kubernetes 1.26

Questions and Answers Preview Questions and Answers Exam Tips

CKA Simulator Kubernetes 1.26

https://killer.sh
Pre Setup

Once you’ve gained access to your terminal it might be wise to spend ~1 minute to setup your environment. You could set these:

alias k=kubectl # will already be pre-configured export do="--dry-run=client -o yaml" # k create deploy nginx --image=nginx $do export now="--force --grace-period 0" # k delete pod x $now

Vim
The following settings will already be configured in your real exam environment in ~/.vimrc. But it can never hurt to be able to type these down:

set tabstop=2 set expandtab set shiftwidth=2

More setup suggestions are in the tips section.

Question 1 | Contexts

Task weight: 1%

You have access to multiple clusters from your main terminal through kubectl contexts. Write all those context names into /opt/course/1/contexts.Next write a command to display the current context into /opt/course/1/context_default_kubectl.sh, the command should use kubectl.Finally write a second command doing the same thing into /opt/course/1/context_default_no_kubectl.sh, but without the use of kubectl.

Answer:

Maybe the fastest way is just to run:

k config get-contexts k config get-contexts -o name > /opt/course/1/contexts Or using jsonpath: k config view -o yaml # overview k config view -o jsonpath="{.contexts[*].name}" k config view -o jsonpath="{.contexts[*].name}" | tr " " "\n" # new lines k config view -o jsonpath="{.contexts[*].name}" | tr " " "\n" > /opt/course/1/contexts

The content should then look like:

#/opt/course/1/contexts k8s-c1-H k8s-c2-AC k8s-c3-CCC

Next create the first command:

# /opt/course/1/context_default_kubectl.sh kubectl config current-context ? sh /opt/course/1/context_default_kubectl.sh k8s-c1-H

And the second one:

# /opt/course/1/context_default_no_kubectl.sh cat ~/.kube/config | grep current ? sh /opt/course/1/context_default_no_kubectl.sh current-context: k8s-c1-H

Notice: In the real exam you might need to filter and find information from bigger lists of resources, hence knowing a little jsonpath and simple bash filtering will be helpful.

The second command could also be improved to:

# /opt/course/1/context_default_no_kubectl.sh cat ~/.kube/config | grep current | sed -e "s/current-context: //"

Question 2 | Schedule Pod on Controlplane Node

Task weight: 3%

Use context: kubectl config use-context k8s-c1-HCreate a single Pod of image httpd:2.4.41-alpine in Namespace default. The Pod should be named pod1 and the container should be named pod1-container. This Pod should only be scheduled on a controlplane node, do not add new labels any nodes.

Answer:
First we find the controlplane node(s) and their taints:

k get node # find controlplane node k describe node cluster1-controlplane1 | grep Taint -A1 # get controlplane node taints k get node cluster1-controlplane1 --show-labels # get controlplane node labels

Next we create the Pod template:

# check the export on the very top of this document so we can use $do k run pod1 --image=httpd:2.4.41-alpine $do > 2.yaml

Perform the necessary changes manually. Use the Kubernetes docs and search for example for tolerations and nodeSelector to find examples:

# 2.yaml apiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:run: pod1name: pod1 spec:containers:- image: httpd:2.4.41-alpinename: pod1-container # changeresources: {}dnsPolicy: ClusterFirstrestartPolicy: Alwaystolerations:- key: "node-role.kubernetes.io/master"operator: "Equal"value: ""effect: "NoSchedule"nodeSelector: # addnode-role.kubernetes.io/control-plane: "" # add status: {}

Important here to add the toleration for running on controlplane nodes, but also the nodeSelector to make sure it only runs on controlplane nodes. If we only specify a toleration the Pod can be scheduled on controlplane or worker nodes.

Now we create it:

k -f 2.yaml create Let's check if the pod is scheduled: ? k get pod pod1 -o wide NAME READY STATUS RESTARTS ... NODE NOMINATED NODE pod1 1/1 Running 0 ... cluster1-controlplane1 <none>

Question 3 | Scale down StatefulSet

Task weight: 1%

Use context: kubectl config use-context k8s-c1-H There are two Pods named o3db-* in Namespace project-c13. C13 management asked you to scale the Pods down to one replica to save resources.

Answer:

If we check the Pods we see two replicas:? k -n project-c13 get pod | grep o3dbo3db-0 1/1 Running 0 52so3db-1 1/1 Running 0 42sFrom their name it looks like these are managed by a StatefulSet. But if we're not sure we could also check for the most common resources which manage Pods:? k -n project-c13 get deploy,ds,sts | grep o3dbstatefulset.apps/o3db 2/2 2m56sConfirmed, we have to work with a StatefulSet. To find this out we could also look at the Pod labels:? k -n project-c13 get pod --show-labels | grep o3dbo3db-0 1/1 Running 0 3m29s app=nginx,controller-revision-hash=o3db-5fbd4bb9cc,statefulset.kubernetes.io/pod-name=o3db-0o3db-1 1/1 Running 0 3m19s app=nginx,controller-revision-hash=o3db-5fbd4bb9cc,statefulset.kubernetes.io/pod-name=o3db-1

To fulfil the task we simply run:

? k -n project-c13 scale sts o3db --replicas 1 statefulset.apps/o3db scaled ? k -n project-c13 get sts o3db NAME READY AGE o3db 1/1 4m39s

C13 Mangement is happy again.

Question 4 | Pod Ready if Service is reachable

Task weight: 4%

Use context: kubectl config use-context k8s-c1-HDo the following in Namespace default. Create a single Pod named ready-if-service-ready of image nginx:1.16.1-alpine. Configure a LivenessProbe which simply executes command true. Also configure a ReadinessProbe which does check if the url http://service-am-i-ready:80 is reachable, you can use wget -T2 -O- http://service-am-i-ready:80 for this. Start the Pod and confirm it isn't ready because of the ReadinessProbe. Create a second Pod named am-i-ready of image nginx:1.16.1-alpine with label id: cross-server-ready. The already existing Service service-am-i-ready should now have that second Pod as endpoint.Now the first Pod should be in ready state, confirm that.

Answer:

It’s a bit of an anti-pattern for one Pod to check another Pod for being ready using probes, hence the normally available readinessProbe.httpGet doesn’t work for absolute remote urls. Still the workaround requested in this task should show how probes and Pod<->Service communication works.

First we create the first Pod:

k run ready-if-service-ready --image=nginx:1.16.1-alpine $do > 4_pod1.yaml

Next perform the necessary additions manually:

# 4_pod1.yaml apiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:run: ready-if-service-readyname: ready-if-service-ready spec:containers:- image: nginx:1.16.1-alpinename: ready-if-service-readyresources: {}livenessProbe: # add from hereexec:command:- 'true'readinessProbe:exec:command:- sh- -c- 'wget -T2 -O- http://service-am-i-ready:80' # to herednsPolicy: ClusterFirstrestartPolicy: Always status: {}

Then create the Pod:

k -f 4_pod1.yaml create

And confirm it’s in a non-ready state:

? k get pod ready-if-service-ready NAME READY STATUS RESTARTS AGE ready-if-service-ready 0/1 Running 0 7s

We can also check the reason for this using describe:

? k describe pod ready-if-service-ready...Warning Unhealthy 18s kubelet, cluster1-node1 Readiness probe failed: Connecting to service-am-i-ready:80 (10.109.194.234:80) wget: download timed out

Now we create the second Pod:

k run am-i-ready --image=nginx:1.16.1-alpine --labels="id=cross-server-ready"

The already existing Service service-am-i-ready should now have an Endpoint:

k describe svc service-am-i-readyk get ep # also possible

Which will result in our first Pod being ready, just give it a minute for the Readiness probe to check again:

? k get pod ready-if-service-ready NAME READY STATUS RESTARTS AGE ready-if-service-ready 1/1 Running 0 53s

Look at these Pods coworking together!

Question 5 | Kubectl sorting

Task weight: 1%

Use context: kubectl config use-context k8s-c1-HThere are various Pods in all namespaces. Write a command into /opt/course/5/find_pods.sh which lists all Pods sorted by their AGE (metadata.creationTimestamp).Write a second command into /opt/course/5/find_pods_uid.sh which lists all Pods sorted by field metadata.uid. Use kubectl sorting for both commands.

Answer:

A good resources here (and for many other things) is the kubectl-cheat-sheet. You can reach it fast when searching for “cheat sheet” in the Kubernetes docs.

# /opt/course/5/find_pods.sh kubectl get pod -A --sort-by=.metadata.creationTimestamp

And to execute:

? sh /opt/course/5/find_pods.sh NAMESPACE NAME ... AGE kube-system kube-scheduler-cluster1-controlplane1 ... 63m kube-system etcd-cluster1-controlplane1 ... 63m kube-system kube-apiserver-cluster1-controlplane1 ... 63m kube-system kube-controller-manager-cluster1-controlplane1 ... 63m ...

For the second command:

# /opt/course/5/find_pods_uid.sh kubectl get pod -A --sort-by=.metadata.uid

And to execute:

? sh /opt/course/5/find_pods_uid.sh NAMESPACE NAME ... AGE kube-system coredns-5644d7b6d9-vwm7g ... 68m project-c13 c13-3cc-runner-heavy-5486d76dd4-ddvlt ... 63m project-hamster web-hamster-shop-849966f479-278vp ... 63m project-c13 c13-3cc-web-646b6c8756-qsg4b ... 63m

Question 6 | Storage, PV, PVC, Pod volume

Task weight: 8%

Use context: kubectl config use-context k8s-c1-HCreate a new PersistentVolume named safari-pv. It should have a capacity of 2Gi, accessMode ReadWriteOnce, hostPath /Volumes/Data and no storageClassName defined.Next create a new PersistentVolumeClaim in Namespace project-tiger named safari-pvc . It should request 2Gi storage, accessMode ReadWriteOnce and should not define a storageClassName. The PVC should bound to the PV correctly.Finally create a new Deployment safari in Namespace project-tiger which mounts that volume at /tmp/safari-data. The Pods of that Deployment should be of image httpd:2.4.41-alpine.

Answer

Find an example from https://kubernetes.io/docs and alter it:# 6_pv.yaml kind: PersistentVolume apiVersion: v1 metadata:name: safari-pv spec:capacity:storage: 2GiaccessModes:- ReadWriteOncehostPath:path: "/Volumes/Data"

Then create it:

k -f 6_pv.yaml create

Next the PersistentVolumeClaim:

Find an example from https://kubernetes.io/docs and alter it:

# 6_pvc.yaml kind: PersistentVolumeClaim apiVersion: v1 metadata:name: safari-pvcnamespace: project-tiger spec:accessModes:- ReadWriteOnceresources:requests:storage: 2Gi

Then create:

k -f 6_pvc.yaml create

And check that both have the status Bound:

? k -n project-tiger get pv,pvcNAME CAPACITY ... STATUS CLAIM ...persistentvolume/safari-pv 2Gi ... Bound project-tiger/safari-pvc ...NAME STATUS VOLUME CAPACITY ...persistentvolumeclaim/safari-pvc Bound safari-pv 2Gi ...

Next we create a Deployment and mount that volume:

k -n project-tiger create deploy safari \--image=httpd:2.4.41-alpine $do > 6_dep.yaml

Alter the yaml to mount the volume:

# 6_dep.yaml apiVersion: apps/v1 kind: Deployment metadata:creationTimestamp: nulllabels:app: safariname: safarinamespace: project-tiger spec:replicas: 1selector:matchLabels:app: safaristrategy: {}template:metadata:creationTimestamp: nulllabels:app: safarispec:volumes: # add- name: data # addpersistentVolumeClaim: # addclaimName: safari-pvc # addcontainers:- image: httpd:2.4.41-alpinename: containervolumeMounts: # add- name: data # addmountPath: /tmp/safari-data # add

Excuet:

k -f 6_dep.yaml create

We can confirm it’s mounting correctly:

? k -n project-tiger describe pod safari-5cbf46d6d-mjhsb | grep -A2 Mounts: Mounts:/tmp/safari-data from data (rw) # there it is/var/run/secrets/kubernetes.io/serviceaccount from default-token-n2sjj (ro)

Question 7 | Node and Pod Resource Usage

Task weight: 1%

Use context: kubectl config use-context k8s-c1-HThe metrics-server has been installed in the cluster. Your college would like to know the kubectl commands to:show Nodes resource usageshow Pods and their containers resource usage Please write the commands into /opt/course/7/node.sh and /opt/course/7/pod.sh.

Answer:

The command we need to use here is top:

? k top -hDisplay Resource (CPU/Memory/Storage) usage.The top command allows you to see the resource consumption for nodes or pods.This command requires Metrics Server to be correctly configured and working on the server.Available Commands:node Display Resource (CPU/Memory/Storage) usage of nodespod Display Resource (CPU/Memory/Storage) usage of pods

We see that the metrics server provides information about resource usage:

? k top nodeNAME CPU(cores) CPU% MEMORY(bytes) MEMORY% cluster1-controlplane1 178m 8% 1091Mi 57% cluster1-node1 66m 6% 834Mi 44% cluster1-node2 91m 9% 791Mi 41%

We create the first file:

# /opt/course/7/node.shkubectl top node

For the second file we might need to check the docs again:

? k top pod -h Display Resource (CPU/Memory/Storage) usage of pods. ... Namespace in current context is ignored even if specified with --namespace.--containers=false: If present, print usage of containers within a pod.--no-headers=false: If present, print output without headers. ...

With this we can finish this task:

# /opt/course/7/pod.sh kubectl top pod --containers=true

Question 8 | Get Controlplane Information

Task weight: 2%

Use context: kubectl config use-context k8s-c1-HSsh into the controlplane node with ssh cluster1-controlplane1. Check how the controlplane components kubelet, kube-apiserver, kube-scheduler, kube-controller-manager and etcd are started/installed on the controlplane node. Also find out the name of the DNS application and how it's started/installed on the controlplane node.Write your findings into file /opt/course/8/controlplane-components.txt. The file should be structured like:# /opt/course/8/controlplane-components.txt kubelet: [TYPE] kube-apiserver: [TYPE] kube-scheduler: [TYPE] kube-controller-manager: [TYPE] etcd: [TYPE] dns: [TYPE] [NAME] Choices of [TYPE] are: not-installed, process, static-pod, pod

Answer:

We could start by finding processes of the requested components, especially the kubelet at first:

? ssh cluster1-controlplane1 root@cluster1-controlplane1:~# ps aux | grep kubelet # shows kubelet process

We can see which components are controlled via systemd looking at /etc/systemd/system directory:

? root@cluster1-controlplane1:~# find /etc/systemd/system/ | grep kube /etc/systemd/system/kubelet.service.d /etc/systemd/system/kubelet.service.d/10-kubeadm.conf /etc/systemd/system/multi-user.target.wants/kubelet.service? root@cluster1-controlplane1:~# find /etc/systemd/system/ | grep etcd

This shows kubelet is controlled via systemd, but no other service named kube nor etcd. It seems that this cluster has been setup using kubeadm, so we check in the default manifests directory:

? root@cluster1-controlplane1:~# find /etc/kubernetes/manifests/ /etc/kubernetes/manifests/ /etc/kubernetes/manifests/kube-controller-manager.yaml /etc/kubernetes/manifests/etcd.yaml /etc/kubernetes/manifests/kube-apiserver.yaml /etc/kubernetes/manifests/kube-scheduler.yaml (The kubelet could also have a different manifests directory specified via parameter --pod-manifest-path in it's systemd startup config)

This means the main 4 controlplane services are setup as static Pods. Actually, let’s check all Pods running on in the kube-system Namespace on the controlplane node:

? root@cluster1-controlplane1:~# kubectl -n kube-system get pod -o wide | grep controlplane1coredns-5644d7b6d9-c4f68 1/1 Running ... cluster1-controlplane1 coredns-5644d7b6d9-t84sc 1/1 Running ... cluster1-controlplane1 etcd-cluster1-controlplane1 1/1 Running ... cluster1-controlplane1 kube-apiserver-cluster1-controlplane1 1/1 Running ... cluster1-controlplane1 kube-controller-manager-cluster1-controlplane1 1/1 Running ... cluster1-controlplane1 kube-proxy-q955p 1/1 Running ... cluster1-controlplane1 kube-scheduler-cluster1-controlplane1 1/1 Running ... cluster1-controlplane1 weave-net-mwj47 2/2 Running ... cluster1-controlplane1

There we see the 5 static pods, with -cluster1-controlplane1 as suffix.

We also see that the dns application seems to be coredns, but how is it controlled?

? root@cluster1-controlplane1$ kubectl -n kube-system get ds NAME DESIRED CURRENT ... NODE SELECTOR AGE kube-proxy 3 3 ... kubernetes.io/os=linux 155m weave-net 3 3 ... <none> 155m? root@cluster1-controlplane1$ kubectl -n kube-system get deploy NAME READY UP-TO-DATE AVAILABLE AGE coredns 2/2 2 2 155m

Seems like coredns is controlled via a Deployment. We combine our findings in the requested file:

# /opt/course/8/controlplane-components.txt kubelet: process kube-apiserver: static-pod kube-scheduler: static-pod kube-controller-manager: static-pod etcd: static-pod dns: pod coredns

You should be comfortable investigating a running cluster, know different methods on how a cluster and its services can be setup and be able to troubleshoot and find error sources.

Question 9 | Kill Scheduler, Manual Scheduling

Task weight: 5%

Use context: kubectl config use-context k8s-c2-ACSsh into the controlplane node with ssh cluster2-controlplane1. Temporarily stop the kube-scheduler, this means in a way that you can start it again afterwards.Create a single Pod named manual-schedule of image httpd:2.4-alpine, confirm it's created but not scheduled on any node.Now you're the scheduler and have all its power, manually schedule that Pod on node cluster2-controlplane1. Make sure it's running.Start the kube-scheduler again and confirm it's running correctly by creating a second Pod named manual-schedule2 of image httpd:2.4-alpine and check if it's running on cluster2-node1.

Answer:
Stop the Scheduler

First we find the controlplane node:

? k get node NAME STATUS ROLES AGE VERSION cluster2-controlplane1 Ready control-plane 26h v1.26.0 cluster2-node1 Ready <none> 26h v1.26.0

Then we connect and check if the scheduler is running:

? ssh cluster2-controlplane1 ? root@cluster2-controlplane1:~# kubectl -n kube-system get pod | grep schedule kube-scheduler-cluster2-controlplane1 1/1 Running 0 6s

Kill the Scheduler (temporarily):

? root@cluster2-controlplane1:~# cd /etc/kubernetes/manifests/ ? root@cluster2-controlplane1:~# mv kube-scheduler.yaml ..

And it should be stopped:

? root@cluster2-controlplane1:~# kubectl -n kube-system get pod | grep schedule ? root@cluster2-controlplane1:~#

Create a Pod
Now we create the Pod:

k run manual-schedule --image=httpd:2.4-alpine

And confirm it has no node assigned:

? k get pod manual-schedule -o wideNAME READY STATUS ... NODE NOMINATED NODE manual-schedule 0/1 Pending ... <none> <none>

Manually schedule the Pod
Let’s play the scheduler now:

k get pod manual-schedule -o yaml > 9.yaml# 9.yaml apiVersion: v1 kind: Pod metadata:creationTimestamp: "2020-09-04T15:51:02Z"labels:run: manual-schedulemanagedFields: ...manager: kubectl-runoperation: Updatetime: "2020-09-04T15:51:02Z"name: manual-schedulenamespace: defaultresourceVersion: "3515"selfLink: /api/v1/namespaces/default/pods/manual-scheduleuid: 8e9d2532-4779-4e63-b5af-feb82c74a935 spec:nodeName: cluster2-controlplane1 # add the controlplane node namecontainers:- image: httpd:2.4-alpineimagePullPolicy: IfNotPresentname: manual-scheduleresources: {}terminationMessagePath: /dev/termination-logterminationMessagePolicy: FilevolumeMounts:- mountPath: /var/run/secrets/kubernetes.io/serviceaccountname: default-token-nxnc7readOnly: truednsPolicy: ClusterFirst ...The only thing a scheduler does, is that it sets the nodeName for a Pod declaration. How it finds the correct node to schedule on, that's a very much complicated matter and takes many variables into account.As we cannot kubectl apply or kubectl edit , in this case we need to delete and create or replace:

k -f 9.yaml replace --force

How does it look?

? k get pod manual-schedule -o wide

NAME READY STATUS … NODE

manual-schedule 1/1 Running … cluster2-controlplane1

It looks like our Pod is running on the controlplane now as requested, although no tolerations were specified. Only the scheduler takes tains/tolerations/affinity into account when finding the correct node name. That's why it's still possible to assign Pods manually directly to a controlplane node and skip the scheduler.Start the scheduler again

? ssh cluster2-controlplane1

? root@cluster2-controlplane1:~# cd /etc/kubernetes/manifests/

? root@cluster2-controlplane1:~# mv …/kube-scheduler.yaml .

Checks it's running:

? root@cluster2-controlplane1:~# kubectl -n kube-system get pod | grep schedule

kube-scheduler-cluster2-controlplane1 1/1 Running 0 16s

Schedule a second test Pod:

k run manual-schedule2 --image=httpd:2.4-alpine

? k get pod -o wide | grep schedule

manual-schedule 1/1 Running … cluster2-controlplane1

manual-schedule2 1/1 Running … cluster2-node1

Back to normal.## Question 10 | RBAC ServiceAccount Role RoleBindingTask weight: 6%

Use context: kubectl config use-context k8s-c1-H

Create a new ServiceAccount processor in Namespace project-hamster. Create a Role and RoleBinding, both named processor as well. These should allow the new SA to only create Secrets and ConfigMaps in that Namespace.

Answer: Let's talk a little about RBAC resourcesA ClusterRole|Role defines a set of permissions and where it is available, in the whole cluster or just a single Namespace.A ClusterRoleBinding|RoleBinding connects a set of permissions with an account and defines where it is applied, in the whole cluster or just a single Namespace.Because of this there are 4 different RBAC combinations and 3 valid ones:Role + RoleBinding (available in single Namespace, applied in single Namespace)ClusterRole + ClusterRoleBinding (available cluster-wide, applied cluster-wide)ClusterRole + RoleBinding (available cluster-wide, applied in single Namespace)Role + ClusterRoleBinding (NOT POSSIBLE: available in single Namespace, applied cluster-wide)To the solutionWe first create the ServiceAccount:

? k -n project-hamster create sa processor

serviceaccount/processor created

Then for the Role:

k -n project-hamster create role -h # examples

So we execute: k -n project-hamster create role processor --verb=create --resource=secret --resource=configmap

Which will create a Role like:

# kubectl -n project-hamster create role processor --verb=create --resource=secret --resource=configmap apiVersion: rbac.authorization.k8s.io/v1 kind: Role metadata:name: processornamespace: project-hamster rules: - apiGroups:- ""resources:- secrets- configmapsverbs:- create

Now we bind the Role to the ServiceAccount:

k -n project-hamster create rolebinding -h # examples

So we create it:

k -n project-hamster create rolebinding processor --role processor --serviceaccount project-hamster:processor

This will create a RoleBinding like:

# kubectl -n project-hamster create rolebinding processor --role processor --serviceaccount project-hamster:processor apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata:name: processornamespace: project-hamster roleRef:apiGroup: rbac.authorization.k8s.iokind: Rolename: processor subjects: - kind: ServiceAccountname: processornamespace: project-hamster

To test our RBAC setup we can use kubectl auth can-i:

k auth can-i -h # examples

Like this:

? k -n project-hamster auth can-i create secret --as system:serviceaccount:project-hamster:processor yes? k -n project-hamster auth can-i create configmap --as system:serviceaccount:project-hamster:processor yes? k -n project-hamster auth can-i create pod --as system:serviceaccount:project-hamster:processor no? k -n project-hamster auth can-i delete secret --as system:serviceaccount:project-hamster:processor no? k -n project-hamster auth can-i get configmap --as system:serviceaccount:project-hamster:processor no

Done.

Question 11 | DaemonSet on all Nodes

Task weight: 4%

Use context: kubectl config use-context k8s-c1-HUse Namespace project-tiger for the following. Create a DaemonSet named ds-important with image httpd:2.4-alpine and labels id=ds-important and uuid=18426a0b-5f59-4e10-923f-c0e078e82462. The Pods it creates should request 10 millicore cpu and 10 mebibyte memory. The Pods of that DaemonSet should run on all nodes, also controlplanes.

Answer:

As of now we aren’t able to create a DaemonSet directly using kubectl, so we create a Deployment and just change it up:

k -n project-tiger create deployment --image=httpd:2.4-alpine ds-important $do > 11.yaml

(Sure you could also search for a DaemonSet example yaml in the Kubernetes docs and alter it.)

Then we adjust the yaml to:

# 11.yaml apiVersion: apps/v1 kind: DaemonSet # change from Deployment to Daemonset metadata:creationTimestamp: nulllabels: # addid: ds-important # adduuid: 18426a0b-5f59-4e10-923f-c0e078e82462 # addname: ds-importantnamespace: project-tiger # important spec:#replicas: 1 # removeselector:matchLabels:id: ds-important # adduuid: 18426a0b-5f59-4e10-923f-c0e078e82462 # add#strategy: {} # removetemplate:metadata:creationTimestamp: nulllabels:id: ds-important # adduuid: 18426a0b-5f59-4e10-923f-c0e078e82462 # addspec:containers:- image: httpd:2.4-alpinename: ds-importantresources:requests: # addcpu: 10m # addmemory: 10Mi # addtolerations: # add- effect: NoSchedule # addkey: node-role.kubernetes.io/control-plane # add #status: {} # remove

It was requested that the DaemonSet runs on all nodes, so we need to specify the toleration for this.

Let’s confirm:

k -f 11.yaml create ? k -n project-tiger get ds NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE ds-important 3 3 3 3 3 <none> 8s ? k -n project-tiger get pod -l id=ds-important -o wide NAME READY STATUS NODE ds-important-6pvgm 1/1 Running ... cluster1-node1 ds-important-lh5ts 1/1 Running ... cluster1-controlplane1 ds-important-qhjcq 1/1 Running ... cluster1-node2

Question 12 | Deployment on all Nodes

Task weight: 6%

Use context: kubectl config use-context k8s-c1-HUse Namespace project-tiger for the following. Create a Deployment named deploy-important with label id=very-important (the Pods should also have this label) and 3 replicas. It should contain two containers, the first named container1 with image nginx:1.17.6-alpine and the second one named container2 with image kubernetes/pause.There should be only ever one Pod of that Deployment running on one worker node. We have two worker nodes: cluster1-node1 and cluster1-node2. Because the Deployment has three replicas the result should be that on both nodes one Pod is running. The third Pod won't be scheduled, unless a new worker node will be added.In a way we kind of simulate the behaviour of a DaemonSet here, but using a Deployment and a fixed number of replicas.

Answer:

There are two possible ways, one using podAntiAffinity and one using topologySpreadConstraint.

PodAntiAffinity

The idea here is that we create a “Inter-pod anti-affinity” which allows us to say a Pod should only be scheduled on a node where another Pod of a specific label (here the same label) is not already running.

Let’s begin by creating the Deployment template:

k -n project-tiger create deployment --image=nginx:1.17.6-alpine deploy-important $do > 12.yaml

Then change the yaml to:

# 12.yaml apiVersion: apps/v1 kind: Deployment metadata:creationTimestamp: nulllabels:id: very-important # changename: deploy-importantnamespace: project-tiger # important spec:replicas: 3 # changeselector:matchLabels:id: very-important # changestrategy: {}template:metadata:creationTimestamp: nulllabels:id: very-important # changespec:containers:- image: nginx:1.17.6-alpinename: container1 # changeresources: {}- image: kubernetes/pause # addname: container2 # addaffinity: # addpodAntiAffinity: # addrequiredDuringSchedulingIgnoredDuringExecution: # add- labelSelector: # addmatchExpressions: # add- key: id # addoperator: In # addvalues: # add- very-important # addtopologyKey: kubernetes.io/hostname # add status: {}

Specify a topologyKey, which is a pre-populated Kubernetes label, you can find this by describing a node.
TopologySpreadConstraints
We can achieve the same with topologySpreadConstraints. Best to try out and play with both.

# 12.yaml apiVersion: apps/v1 kind: Deployment metadata:creationTimestamp: nulllabels:id: very-important # changename: deploy-importantnamespace: project-tiger # important spec:replicas: 3 # changeselector:matchLabels:id: very-important # changestrategy: {}template:metadata:creationTimestamp: nulllabels:id: very-important # changespec:containers:- image: nginx:1.17.6-alpinename: container1 # changeresources: {}- image: kubernetes/pause # addname: container2 # addtopologySpreadConstraints: # add- maxSkew: 1 # addtopologyKey: kubernetes.io/hostname # addwhenUnsatisfiable: DoNotSchedule # addlabelSelector: # addmatchLabels: # addid: very-important # add status: {}

Apply and Run
Let’s run it:

k -f 12.yaml create

Then we check the Deployment status where it shows 2/3 ready count:

? k -n project-tiger get deploy -l id=very-important NAME READY UP-TO-DATE AVAILABLE AGE deploy-important 2/3 3 2 2m35s

And running the following we see one Pod on each worker node and one not scheduled.

? k -n project-tiger get pod -o wide -l id=very-important NAME READY STATUS ... NODE deploy-important-58db9db6fc-9ljpw 2/2 Running ... cluster1-node1 deploy-important-58db9db6fc-lnxdb 0/2 Pending ... <none> deploy-important-58db9db6fc-p2rz8 2/2 Running ... cluster1-node2

If we kubectl describe the Pod deploy-important-58db9db6fc-lnxdb it will show us the reason for not scheduling is our implemented podAntiAffinity ruling:

Warning FailedScheduling 63s (x3 over 65s) default-scheduler 0/3 nodes are available: 1 node(s) had taint {node-role.kubernetes.io/control-plane: }, that the pod didn’t tolerate, 2 node(s) didn’t match pod affinity/anti-affinity, 2 node(s) didn’t satisfy existing pods anti-affinity rules.

Or our topologySpreadConstraints:

Warning FailedScheduling 16s default-scheduler 0/3 nodes are available: 1 node(s) had taint {node-role.kubernetes.io/control-plane: }, that the pod didn’t tolerate, 2 node(s) didn’t match pod topology spread constraints.

Question 13 | Multi Containers and Pod shared Volume

Task weight: 4%

Use context: kubectl config use-context k8s-c1-HCreate a Pod named multi-container-playground in Namespace default with three containers, named c1, c2 and c3. There should be a volume attached to that Pod and mounted into every container, but the volume shouldn't be persisted or shared with other Pods.Container c1 should be of image nginx:1.17.6-alpine and have the name of the node where its Pod is running available as environment variable MY_NODE_NAME.Container c2 should be of image busybox:1.31.1 and write the output of the date command every second in the shared volume into file date.log. You can use while true; do date >> /your/vol/path/date.log; sleep 1; done for this.Container c3 should be of image busybox:1.31.1 and constantly send the content of file date.log from the shared volume to stdout. You can use tail -f /your/vol/path/date.log for this.Check the logs of container c3 to confirm correct setup.

Answer:

First we create the Pod template:

k run multi-container-playground --image=nginx:1.17.6-alpine $do > 13.yaml

And add the other containers and the commands they should execute:

# 13.yaml apiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:run: multi-container-playgroundname: multi-container-playground spec:containers:- image: nginx:1.17.6-alpinename: c1 # changeresources: {}env: # add- name: MY_NODE_NAME # addvalueFrom: # addfieldRef: # addfieldPath: spec.nodeName # addvolumeMounts: # add- name: vol # addmountPath: /vol # add- image: busybox:1.31.1 # addname: c2 # addcommand: ["sh", "-c", "while true; do date >> /vol/date.log; sleep 1; done"] # addvolumeMounts: # add- name: vol # addmountPath: /vol # add- image: busybox:1.31.1 # addname: c3 # addcommand: ["sh", "-c", "tail -f /vol/date.log"] # addvolumeMounts: # add- name: vol # addmountPath: /vol # adddnsPolicy: ClusterFirstrestartPolicy: Alwaysvolumes: # add- name: vol # addemptyDir: {} # add status: {} k -f 13.yaml create

Oh boy, lot’s of requested things. We check if everything is good with the Pod:

? k get pod multi-container-playgroundNAME READY STATUS RESTARTS AGEmulti-container-playground 3/3 Running 0 95s

Good, then we check if container c1 has the requested node name as env variable:

? k exec multi-container-playground -c c1 -- env | grep MY MY_NODE_NAME=cluster1-node2

And finally we check the logging:

? k logs multi-container-playground -c c3 Sat Dec 7 16:05:10 UTC 2077 Sat Dec 7 16:05:11 UTC 2077 Sat Dec 7 16:05:12 UTC 2077 Sat Dec 7 16:05:13 UTC 2077 Sat Dec 7 16:05:14 UTC 2077 Sat Dec 7 16:05:15 UTC 2077 Sat Dec 7 16:05:16 UTC 2077

Question 14 | Find out Cluster Information

Task weight: 2%

Use context: kubectl config use-context k8s-c1-HYou're ask to find out following information about the cluster k8s-c1-H:How many controlplane nodes are available?How many worker nodes are available?What is the Service CIDR?Which Networking (or CNI Plugin) is configured and where is its config file?Which suffix will static pods have that run on cluster1-node1?Write your answers into file /opt/course/14/cluster-info, structured like this:# /opt/course/14/cluster-info1: [ANSWER]2: [ANSWER]3: [ANSWER]4: [ANSWER]5: [ANSWER]

Answer:
How many controlplane and worker nodes are available?

? k get node NAME STATUS ROLES AGE VERSION cluster1-controlplane1 Ready control-plane 27h v1.26.0 cluster1-node1 Ready <none> 27h v1.26.0 cluster1-node2 Ready <none> 27h v1.26.0

We see one controlplane and two workers.

What is the Service CIDR? ? ssh cluster1-controlplane1 ? root@cluster1-controlplane1:~# cat /etc/kubernetes/manifests/kube-apiserver.yaml | grep range- --service-cluster-ip-range=10.96.0.0/12

Which Networking (or CNI Plugin) is configured and where is its config file?

? root@cluster1-controlplane1:~# find /etc/cni/net.d/ /etc/cni/net.d/ /etc/cni/net.d/10-weave.conflist? root@cluster1-controlplane1:~# cat /etc/cni/net.d/10-weave.conflist {"cniVersion": "0.3.0","name": "weave",...

By default the kubelet looks into /etc/cni/net.d to discover the CNI plugins. This will be the same on every controlplane and worker nodes.

Which suffix will static pods have that run on cluster1-node1?

The suffix is the node hostname with a leading hyphen. It used to be -static in earlier Kubernetes versions.

Result

The resulting /opt/course/14/cluster-info could look like:

# /opt/course/14/cluster-info # How many controlplane nodes are available? 1: 1# How many worker nodes are available? 2: 2# What is the Service CIDR? 3: 10.96.0.0/12# Which Networking (or CNI Plugin) is configured and where is its config file? 4: Weave, /etc/cni/net.d/10-weave.conflist# Which suffix will static pods have that run on cluster1-node1? 5: -cluster1-node1

Question 15 | Cluster Event Logging

Task weight: 3%

Use context: kubectl config use-context k8s-c2-ACWrite a command into /opt/course/15/cluster_events.sh which shows the latest events in the whole cluster, ordered by time (metadata.creationTimestamp). Use kubectl for it. Now kill the kube-proxy Pod running on node cluster2-node1 and write the events this caused into /opt/course/15/pod_kill.log. Finally kill the containerd container of the kube-proxy Pod on node cluster2-node1 and write the events into /opt/course/15/container_kill.log. Do you notice differences in the events both actions caused?

Answer:

# /opt/course/15/cluster_events.sh kubectl get events -A --sort-by=.metadata.creationTimestamp

Now we kill the kube-proxy Pod:

k -n kube-system get pod -o wide | grep proxy # find pod running on cluster2-node1 k -n kube-system delete pod kube-proxy-z64cg

Now check the events:

sh /opt/course/15/cluster_events.sh

Write the events the killing caused into /opt/course/15/pod_kill.log:

# /opt/course/15/pod_kill.log kube-system 9s Normal Killing pod/kube-proxy-jsv7t ... kube-system 3s Normal SuccessfulCreate daemonset/kube-proxy ... kube-system <unknown> Normal Scheduled pod/kube-proxy-m52sx ... default 2s Normal Starting node/cluster2-node1 ... kube-system 2s Normal Created pod/kube-proxy-m52sx ... kube-system 2s Normal Pulled pod/kube-proxy-m52sx ... kube-system 2s Normal Started pod/kube-proxy-m52sx ...

Finally we will try to provoke events by killing the container belonging to the container of the kube-proxy Pod:

? ssh cluster2-node1 ? root@cluster2-node1:~# crictl ps | grep kube-proxy 1e020b43c4423 36c4ebbc9d979 About an hour ago Running kube-proxy ... ? root@cluster2-node1:~# crictl rm 1e020b43c4423 1e020b43c4423 ? root@cluster2-node1:~# crictl ps | grep kube-proxy 0ae4245707910 36c4ebbc9d979 17 seconds ago Running kube-proxy ...

We killed the main container (1e020b43c4423), but also noticed that a new container (0ae4245707910) was directly created. Thanks Kubernetes!
Now we see if this caused events again and we write those into the second file:

sh /opt/course/15/cluster_events.sh# /opt/course/15/container_kill.log kube-system 13s Normal Created pod/kube-proxy-m52sx ... kube-system 13s Normal Pulled pod/kube-proxy-m52sx ... kube-system 13s Normal Started pod/kube-proxy-m52sx ...

Comparing the events we see that when we deleted the whole Pod there were more things to be done, hence more events. For example was the DaemonSet in the game to re-create the missing Pod. Where when we manually killed the main container of the Pod, the Pod would still exist but only its container needed to be re-created, hence less events.

Question 16 | Namespaces and Api Resources

Task weight: 2%

Use context: kubectl config use-context k8s-c1-HWrite the names of all namespaced Kubernetes resources (like Pod, Secret, ConfigMap...) into /opt/course/16/resources.txt. Find the project-* Namespace with the highest number of Roles defined in it and write its name and amount of Roles into /opt/course/16/crowded-namespace.txt.

Answer:
Namespace and Namespaces Resources
Now we can get a list of all resources like:

k api-resources # shows all k api-resources -h # help always good k api-resources --namespaced -o name > /opt/course/16/resources.txt Which results in the file: # /opt/course/16/resources.txt bindings configmaps endpoints events limitranges persistentvolumeclaims pods podtemplates replicationcontrollers resourcequotas secrets serviceaccounts services controllerrevisions.apps daemonsets.apps deployments.apps replicasets.apps statefulsets.apps localsubjectaccessreviews.authorization.k8s.io horizontalpodautoscalers.autoscaling cronjobs.batch jobs.batch leases.coordination.k8s.io events.events.k8s.io ingresses.extensions ingresses.networking.k8s.io networkpolicies.networking.k8s.io poddisruptionbudgets.policy rolebindings.rbac.authorization.k8s.io roles.rbac.authorization.k8s.io

Namespace with most Roles:

? k -n project-c13 get role --no-headers | wc -l No resources found in project-c13 namespace. 0? k -n project-c14 get role --no-headers | wc -l 300? k -n project-hamster get role --no-headers | wc -l No resources found in project-hamster namespace. 0? k -n project-snake get role --no-headers | wc -l No resources found in project-snake namespace. 0? k -n project-tiger get role --no-headers | wc -l No resources found in project-tiger namespace. 0

Finally we write the name and amount into the file:

# /opt/course/16/crowded-namespace.txtproject-c14 with 300 resources

Question 17 | Find Container of Pod and check info

Task weight: 3%

Use context: kubectl config use-context k8s-c1-HIn Namespace project-tiger create a Pod named tigers-reunite of image httpd:2.4.41-alpine with labels pod=container and container=pod. Find out on which node the Pod is scheduled. Ssh into that node and find the containerd container belonging to that Pod. Using command crictl:Write the ID of the container and the info.runtimeType into /opt/course/17/pod-container.txtWrite the logs of the container into /opt/course/17/pod-container.log

Answer:

First we create the Pod:

k -n project-tiger run tigers-reunite --image=httpd:2.4.41-alpine --labels "pod=container,container=pod"

Next we find out the node it’s scheduled on:

k -n project-tiger get pod -o wide

or fancy:

k -n project-tiger get pod tigers-reunite -o jsonpath="{.spec.nodeName}"

Then we ssh into that node and and check the container info:

? ssh cluster1-node2 ? root@cluster1-node2:~# crictl ps | grep tigers-reunite b01edbe6f89ed 54b0995a63052 5 seconds ago Running tigers-reunite ...? root@cluster1-node2:~# crictl inspect b01edbe6f89ed | grep runtimeType"runtimeType": "io.containerd.runc.v2",

Then we fill the requested file (on the main terminal):

# /opt/course/17/pod-container.txt b01edbe6f89ed io.containerd.runc.v2

Finally we write the container logs in the second file:

ssh cluster1-node2 'crictl logs b01edbe6f89ed' &> /opt/course/17/pod-container.log The &> in above's command redirects both the standard output and standard error.

You could also simply run crictl logs on the node and copy the content manually, if it’s not a lot. The file should look like:

# /opt/course/17/pod-container.log AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 10.44.0.37. Set the 'ServerName' directive globally to suppress this message AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 10.44.0.37. Set the 'ServerName' directive globally to suppress this message [Mon Sep 13 13:32:18.555280 2021] [mpm_event:notice] [pid 1:tid 139929534545224] AH00489: Apache/2.4.41 (Unix) configured -- resuming normal operations [Mon Sep 13 13:32:18.555610 2021] [core:notice] [pid 1:tid 139929534545224] AH00094: Command line: 'httpd -D FOREGROUND'

Question 18 | Fix Kubelet

Task weight: 8%

Use context: kubectl config use-context k8s-c3-CCCThere seems to be an issue with the kubelet not running on cluster3-node1. Fix it and confirm that cluster has node cluster3-node1 available in Ready state afterwards. You should be able to schedule a Pod on cluster3-node1 afterwards.Write the reason of the issue into /opt/course/18/reason.txt.

Answer:

The procedure on tasks like these should be to check if the kubelet is running, if not start it, then check its logs and correct errors if there are some.

Always helpful to check if other clusters already have some of the components defined and running, so you can copy and use existing config files. Though in this case it might not need to be necessary.

Check node status:

? k get nodeNAME STATUS ROLES AGE VERSION cluster3-controlplane1 Ready control-plane 14d v1.26.0 cluster3-node1 NotReady <none> 14d v1.26.0

First we check if the kubelet is running:

? ssh cluster3-node1 ? root@cluster3-node1:~# ps aux | grep kubelet root 29294 0.0 0.2 14856 1016 pts/0 S+ 11:30 0:00 grep --color=auto kubelet Nope, so we check if it's configured using systemd as service: ? root@cluster3-node1:~# service kubelet status ● kubelet.service - kubelet: The Kubernetes Node AgentLoaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)Drop-In: /etc/systemd/system/kubelet.service.d└─10-kubeadm.confActive: inactive (dead) since Sun 2019-12-08 11:30:06 UTC; 50min 52s ago

Yes, it’s configured as a service with config at /etc/systemd/system/kubelet.service.d/10-kubeadm.conf, but we see it’s inactive. Let’s try to start it:

? root@cluster3-node1:~# service kubelet start ? root@cluster3-node1:~# service kubelet status ● kubelet.service - kubelet: The Kubernetes Node AgentLoaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)Drop-In: /etc/systemd/system/kubelet.service.d└─10-kubeadm.confActive: activating (auto-restart) (Result: exit-code) since Thu 2020-04-30 22:03:10 UTC; 3s agoDocs: https://kubernetes.io/docs/home/Process: 5989 ExecStart=/usr/local/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS (code=exited, status=203/EXEC)Main PID: 5989 (code=exited, status=203/EXEC) Apr 30 22:03:10 cluster3-node1 systemd[5989]: kubelet.service: Failed at step EXEC spawning /usr/local/bin/kubelet: No such file or directory Apr 30 22:03:10 cluster3-node1 systemd[1]: kubelet.service: Main process exited, code=exited, status=203/EXEC Apr 30 22:03:10 cluster3-node1 systemd[1]: kubelet.service: Failed with result 'exit-code'.

We see it’s trying to execute /usr/local/bin/kubelet with some parameters defined in its service config file. A good way to find errors and get more logs is to run the command manually (usually also with its parameters).

? root@cluster3-node1:~# /usr/local/bin/kubelet -bash: /usr/local/bin/kubelet: No such file or directory ? root@cluster3-node1:~# whereis kubelet kubelet: /usr/bin/kubelet

Another way would be to see the extended logging of a service like using journalctl -u kubelet.

Well, there we have it, wrong path specified. Correct the path in file /etc/systemd/system/kubelet.service.d/10-kubeadm.conf and run:

vim /etc/systemd/system/kubelet.service.d/10-kubeadm.conf # fix

systemctl daemon-reload && systemctl restart kubelet systemctl status kubelet # should now show running

Also the node should be available for the api server, give it a bit of time though:

? k get node NAME STATUS ROLES AGE VERSION cluster3-controlplane1 Ready control-plane 14d v1.26.0 cluster3-node1 Ready <none> 14d v1.26.0

Finally we write the reason into the file:

# /opt/course/18/reason.txt wrong path to kubelet binary specified in service config

Question 19 | Create Secret and mount into Pod

Task weight: 3%

NOTE: This task can only be solved if questions 18 or 20 have been successfully implemented and the k8s-c3-CCC cluster has a functioning worker node Use context: kubectl config use-context k8s-c3-CCCDo the following in a new Namespace secret. Create a Pod named secret-pod of image busybox:1.31.1 which should keep running for some time.There is an existing Secret located at /opt/course/19/secret1.yaml, create it in the Namespace secret and mount it readonly into the Pod at /tmp/secret1.Create a new Secret in Namespace secret called secret2 which should contain user=user1 and pass=1234. These entries should be available inside the Pod's container as environment variables APP_USER and APP_PASS.Confirm everything is working.

Answer

First we create the Namespace and the requested Secrets in it:

k create ns secret cp /opt/course/19/secret1.yaml 19_secret1.yaml

We need to adjust the Namespace for that Secret:

# 19_secret1.yaml apiVersion: v1 data:halt: IyEgL2Jpbi9zaAo... kind: Secret metadata:creationTimestamp: nullname: secret1namespace: secret # change k -f 19_secret1.yaml create

Next we create the second Secret:

k -n secret create secret generic secret2 --from-literal=user=user1 --from-literal=pass=1234

Now we create the Pod template:

k -n secret run secret-pod --image=busybox:1.31.1 $do -- sh -c "sleep 5d" > 19.yaml

Then make the necessary changes:

# 19.yaml apiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:run: secret-podname: secret-podnamespace: secret # add spec:containers:- args:- sh- -c- sleep 1dimage: busybox:1.31.1name: secret-podresources: {}env: # add- name: APP_USER # addvalueFrom: # addsecretKeyRef: # addname: secret2 # addkey: user # add- name: APP_PASS # addvalueFrom: # addsecretKeyRef: # addname: secret2 # addkey: pass # addvolumeMounts: # add- name: secret1 # addmountPath: /tmp/secret1 # addreadOnly: true # adddnsPolicy: ClusterFirstrestartPolicy: Alwaysvolumes: # add- name: secret1 # addsecret: # addsecretName: secret1 # add status: {}

It might not be necessary in current K8s versions to specify the readOnly: true because it’s the default setting anyways.

And execute:

k -f 19.yaml create

Finally we check if all is correct:

? k -n secret exec secret-pod -- env | grep APP APP_PASS=1234 APP_USER=user1? k -n secret exec secret-pod -- find /tmp/secret1 /tmp/secret1 /tmp/secret1/..data /tmp/secret1/halt /tmp/secret1/..2019_12_08_12_15_39.463036797 /tmp/secret1/..2019_12_08_12_15_39.463036797/halt ? k -n secret exec secret-pod -- cat /tmp/secret1/halt #! /bin/sh ### BEGIN INIT INFO # Provides: halt # Required-Start: # Required-Stop: # Default-Start: # Default-Stop: 0 # Short-Description: Execute the halt command. # Description: ...

All is good.

Question 20 | Update Kubernetes Version and join cluster

Task weight: 10%

Use context: kubectl config use-context k8s-c3-CCCYour coworker said node cluster3-node2 is running an older Kubernetes version and is not even part of the cluster. Update Kubernetes on that node to the exact version that's running on cluster3-controlplane1. Then add this node to the cluster. Use kubeadm for this.

Answer:

Upgrade Kubernetes to cluster3-controlplane1 version

Search in the docs for kubeadm upgrade: https://kubernetes.io/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade

? k get nodeNAME STATUS ROLES AGE VERSION cluster3-controlplane1 Ready control-plane 22h v1.26.0 cluster3-node1 Ready <none> 22h v1.26.0

Controlplane node seems to be running Kubernetes 1.26.0 and cluster3-node2 is not yet part of the cluster.

? ssh cluster3-node2 ? root@cluster3-node2:~# kubeadm version kubeadm version: &version.Info{Major:"1", Minor:"26", GitVersion:"v1.26.0", GitCommit:"b46a3f887ca979b1a5d14fd39cb1af43e7e5d12d", GitTreeState:"clean", BuildDate:"2022-12-08T19:57:06Z", GoVersion:"go1.19.4", Compiler:"gc", Platform:"linux/amd64"}? root@cluster3-node2:~# kubectl version --short Client Version: v1.25.5 Kustomize Version: v4.5.7? root@cluster3-node2:~# kubelet --version Kubernetes v1.25.5

Here kubeadm is already installed in the wanted version, so we don’t need to install it. Hence we can run:

? root@cluster3-node2:~# kubeadm upgrade node couldn't create a Kubernetes client from file "/etc/kubernetes/kubelet.conf": failed to load admin kubeconfig: open /etc/kubernetes/kubelet.conf: no such file or directoryTo see the stack trace of this error execute with --v=5 or higherThis is usually the proper command to upgrade a node. But this error means that this node was never even initialised, so nothing to update here. This will be done later using kubeadm join. For now we can continue with kubelet and kubectl:? root@cluster3-node2:~# apt update...Fetched 5,775 kB in 2s (2,313 kB/s) Reading package lists... Done Building dependency tree Reading state information... Done 90 packages can be upgraded. Run 'apt list --upgradable' to see them.? root@cluster3-node2:~# apt show kubectl -a | grep 1.26 Version: 1.26.0-00? root@cluster3-node2:~# apt install kubectl=1.26.0-00 kubelet=1.26.0-00 Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be upgraded:kubectl kubelet 2 upgraded, 0 newly installed, 0 to remove and 135 not upgraded. Need to get 30.5 MB of archives. After this operation, 9,996 kB of additional disk space will be used. Get:1 https://packages.cloud.google.com/apt kubernetes-xenial/main amd64 kubectl amd64 1.26.0-00 [10.1 MB] Get:2 https://packages.cloud.google.com/apt kubernetes-xenial/main amd64 kubelet amd64 1.26.0-00 [20.5 MB] Fetched 30.5 MB in 1s (29.7 MB/s) (Reading database ... 112508 files and directories currently installed.) Preparing to unpack .../kubectl_1.26.0-00_amd64.deb ... Unpacking kubectl (1.26.0-00) over (1.25.5-00) ... Preparing to unpack .../kubelet_1.26.0-00_amd64.deb ... Unpacking kubelet (1.26.0-00) over (1.25.5-00) ... Setting up kubectl (1.26.0-00) ... Setting up kubelet (1.26.0-00) ...? root@cluster3-node2:~# kubelet --version Kubernetes v1.26.0

Now we’re up to date with kubeadm, kubectl and kubelet. Restart the kubelet:

? root@cluster3-node2:~# service kubelet restart ? root@cluster3-node2:~# service kubelet status ● kubelet.service - kubelet: The Kubernetes Node AgentLoaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)Drop-In: /etc/systemd/system/kubelet.service.d└─10-kubeadm.confActive: activating (auto-restart) (Result: exit-code) since Wed 2022-12-21 16:29:26 UTC; 5s agoDocs: https://kubernetes.io/docs/home/Process: 32111 ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS (code=exited, status=1/FAILURE)Main PID: 32111 (code=exited, status=1/FAILURE) Dec 21 16:29:26 cluster3-node2 systemd[1]: kubelet.service: Main process exited, code=exited, status=1/FAILURE Dec 21 16:29:26 cluster3-node2 systemd[1]: kubelet.service: Failed with result 'exit-code'. These errors occur because we still need to run kubeadm join to join the node into the cluster. Let's do this in the next step.

Add cluster3-node2 to cluster:
First we log into the controlplane1 and generate a new TLS bootstrap token, also printing out the join command:

? ssh cluster3-controlplane1 ? root@cluster3-controlplane1:~# kubeadm token create --print-join-command kubeadm join 192.168.100.31:6443 --token rbhrjh.4o93r31o18an6dll --discovery-token-ca-cert-hash sha256:d94524f9ab1eed84417414c7def5c1608f84dbf04437d9f5f73eb6255dafdb18? root@cluster3-controlplane1:~# kubeadm token list TOKEN TTL EXPIRES ... 44dz0t.2lgmone0i1o5z9fe <forever> <never> 4u477f.nmpq48xmpjt6weje 1h 2022-12-21T18:14:30Z rbhrjh.4o93r31o18an6dll 23h 2022-12-22T16:29:58Z

We see the expiration of 23h for our token, we could adjust this by passing the ttl argument.

Next we connect again to cluster3-node2 and simply execute the join command:

? ssh cluster3-node2 ? root@cluster3-node2:~# kubeadm join 192.168.100.31:6443 --token rbhrjh.4o93r31o18an6dll --discovery-token-ca-cert-hash sha256:d94524f9ab1eed84417414c7def5c1608f84dbf04437d9f5f73eb6255dafdb18 [preflight] Running pre-flight checks [preflight] Reading configuration from the cluster... [preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml' [kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml" [kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env" [kubelet-start] Starting the kubelet [kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap... This node has joined the cluster: * Certificate signing request was sent to apiserver and a response was received. * The Kubelet was informed of the new secure connection details. Run 'kubectl get nodes' on the control-plane to see this node join the cluster.? root@cluster3-node2:~# service kubelet status ● kubelet.service - kubelet: The Kubernetes Node AgentLoaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)Drop-In: /etc/systemd/system/kubelet.service.d└─10-kubeadm.confActive: active (running) since Wed 2022-12-21 16:32:19 UTC; 1min 4s agoDocs: https://kubernetes.io/docs/home/Main PID: 32510 (kubelet)Tasks: 11 (limit: 462)Memory: 55.2MCGroup: /system.slice/kubelet.service└─32510 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --container-runti>

If you have troubles with kubeadm join you might need to run kubeadm reset.

This looks great though for us. Finally we head back to the main terminal and check the node status:

? k get nodeNAME STATUS ROLES AGE VERSION cluster3-controlplane1 Ready control-plane 22h v1.26.0 cluster3-node1 Ready <none> 22h v1.26.0 cluster3-node2 NotReady <none> 22h v1.26.0

Give it a bit of time till the node is ready.

? k get nodeNAME STATUS ROLES AGE VERSION cluster3-controlplane1 Ready control-plane 22h v1.26.0 cluster3-node1 Ready <none> 22h v1.26.0 cluster3-node2 Ready <none> 22h v1.26.0

We see cluster3-node2 is now available and up to date.

Question 21 | Create a Static Pod and Service

Task weight: 2%

Use context: kubectl config use-context k8s-c3-CCCCreate a Static Pod named my-static-pod in Namespace default on cluster3-controlplane1. It should be of image nginx:1.16-alpine and have resource requests for 10m CPU and 20Mi memory.Then create a NodePort Service named static-pod-service which exposes that static Pod on port 80 and check if it has Endpoints and if it's reachable through the cluster3-controlplane1 internal IP address. You can connect to the internal node IPs from your main terminal.

Answer:

? ssh cluster3-controlplane1 ? root@cluster1-controlplane1:~# cd /etc/kubernetes/manifests/ ? root@cluster1-controlplane1:~# kubectl run my-static-pod --image=nginx:1.16-alpine -o yaml --dry-run=client > my-static-pod.yaml

Then edit the my-static-pod.yaml to add the requested resource requests:

# /etc/kubernetes/manifests/my-static-pod.yaml apiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:run: my-static-podname: my-static-pod spec:containers:- image: nginx:1.16-alpinename: my-static-podresources:requests:cpu: 10mmemory: 20MidnsPolicy: ClusterFirstrestartPolicy: Always status: {}

And make sure it’s running:

? k get pod -A | grep my-static NAMESPACE NAME READY STATUS ... AGE default my-static-pod-cluster3-controlplane1 1/1 Running ... 22s

Now we expose that static Pod:

k expose pod my-static-pod-cluster3-controlplane1 --name static-pod-service --type=NodePort --port 80

This would generate a Service like:

# kubectl expose pod my-static-pod-cluster3-controlplane1 --name static-pod-service --type=NodePort --port 80apiVersion: v1 kind: Service metadata:creationTimestamp: nulllabels:run: my-static-podname: static-pod-service spec:ports:- port: 80protocol: TCPtargetPort: 80selector:run: my-static-podtype: NodePort status:loadBalancer: {}

Then run and test:

? k get svc,ep -l run=my-static-pod NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/static-pod-service NodePort 10.99.168.252 <none> 80:30352/TCP 30s NAME ENDPOINTS AGE endpoints/static-pod-service 10.32.0.4:80 30s

Looking good.

Question 22 | Check how long certificates are valid

Task weight: 2%

Use context: kubectl config use-context k8s-c2-ACCheck how long the kube-apiserver server certificate is valid on cluster2-controlplane1. Do this with openssl or cfssl. Write the exipiration date into /opt/course/22/expiration.Also run the correct kubeadm command to list the expiration dates and confirm both methods show the same date.Write the correct kubeadm command that would renew the apiserver server certificate into /opt/course/22/kubeadm-renew-certs.sh.

Answer:

First let’s find that certificate:

? ssh cluster2-controlplane1 ? root@cluster2-controlplane1:~# find /etc/kubernetes/pki | grep apiserver /etc/kubernetes/pki/apiserver.crt /etc/kubernetes/pki/apiserver-etcd-client.crt /etc/kubernetes/pki/apiserver-etcd-client.key /etc/kubernetes/pki/apiserver-kubelet-client.crt /etc/kubernetes/pki/apiserver.key /etc/kubernetes/pki/apiserver-kubelet-client.key

Next we use openssl to find out the expiration date:

? root@cluster2-controlplane1:~# openssl x509 -noout -text -in /etc/kubernetes/pki/apiserver.crt | grep Validity -A2ValidityNot Before: Dec 20 18:05:20 2022 GMTNot After : Dec 20 18:05:20 2023 GMT

There we have it, so we write it in the required location on our main terminal:

# /opt/course/22/expiration Dec 20 18:05:20 2023 GMT

And we use the feature from kubeadm to get the expiration too:

? root@cluster2-controlplane1:~# kubeadm certs check-expiration | grep apiserverapiserver Jan 14, 2022 18:49 UTC 363d ca no apiserver-etcd-client Jan 14, 2022 18:49 UTC 363d etcd-ca no apiserver-kubelet-client Jan 14, 2022 18:49 UTC 363d ca no

Looking good. And finally we write the command that would renew all certificates into the requested location:

# /opt/course/22/kubeadm-renew-certs.sh kubeadm certs renew apiserver

Question 23 | Kubelet client/server cert info

Task weight: 2%

Use context: kubectl config use-context k8s-c2-ACNode cluster2-node1 has been added to the cluster using kubeadm and TLS bootstrapping.Find the "Issuer" and "Extended Key Usage" values of the cluster2-node1:kubelet client certificate, the one used for outgoing connections to the kube-apiserver.kubelet server certificate, the one used for incoming connections from the kube-apiserver.Write the information into file /opt/course/23/certificate-info.txt.Compare the "Issuer" and "Extended Key Usage" fields of both certificates and make sense of these.

Answer:

To find the correct kubelet certificate directory, we can look for the default value of the --cert-dir parameter for the kubelet. For this search for “kubelet” in the Kubernetes docs which will lead to: https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet. We can check if another certificate directory has been configured using ps aux or in /etc/systemd/system/kubelet.service.d/10-kubeadm.conf.

First we check the kubelet client certificate:

? ssh cluster2-node1 ? root@cluster2-node1:~# openssl x509 -noout -text -in /var/lib/kubelet/pki/kubelet-client-current.pem | grep IssuerIssuer: CN = kubernetes ? root@cluster2-node1:~# openssl x509 -noout -text -in /var/lib/kubelet/pki/kubelet-client-current.pem | grep "Extended Key Usage" -A1X509v3 Extended Key Usage: TLS Web Client Authentication

Next we check the kubelet server certificate:

? root@cluster2-node1:~# openssl x509 -noout -text -in /var/lib/kubelet/pki/kubelet.crt | grep IssuerIssuer: CN = cluster2-node1-ca@1588186506 ? root@cluster2-node1:~# openssl x509 -noout -text -in /var/lib/kubelet/pki/kubelet.crt | grep "Extended Key Usage" -A1X509v3 Extended Key Usage: TLS Web Server Authentication

We see that the server certificate was generated on the worker node itself and the client certificate was issued by the Kubernetes api. The “Extended Key Usage” also shows if it’s for client or server authentication.

More about this: https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping

Question 24 | NetworkPolicy

Task weight: 9%

Use context: kubectl config use-context k8s-c1-HThere was a security incident where an intruder was able to access the whole cluster from a single hacked backend Pod.To prevent this create a NetworkPolicy called np-backend in Namespace project-snake. It should allow the backend-* Pods only to:connect to db1-* Pods on port 1111connect to db2-* Pods on port 2222Use the app label of Pods in your policy.After implementation, connections from backend-* Pods to vault-* Pods on port 3333 should for example no longer work.

Answer:

First we look at the existing Pods and their labels:

? k -n project-snake get pod NAME READY STATUS RESTARTS AGE backend-0 1/1 Running 0 8s db1-0 1/1 Running 0 8s db2-0 1/1 Running 0 10s vault-0 1/1 Running 0 10s? k -n project-snake get pod -L app NAME READY STATUS RESTARTS AGE APP backend-0 1/1 Running 0 3m15s backend db1-0 1/1 Running 0 3m15s db1 db2-0 1/1 Running 0 3m17s db2 vault-0 1/1 Running 0 3m17s vault

We test the current connection situation and see nothing is restricted:

? k -n project-snake get pod -o wide NAME READY STATUS RESTARTS AGE IP ... backend-0 1/1 Running 0 4m14s 10.44.0.24 ... db1-0 1/1 Running 0 4m14s 10.44.0.25 ... db2-0 1/1 Running 0 4m16s 10.44.0.23 ... vault-0 1/1 Running 0 4m16s 10.44.0.22 ...? k -n project-snake exec backend-0 -- curl -s 10.44.0.25:1111 database one? k -n project-snake exec backend-0 -- curl -s 10.44.0.23:2222 database two? k -n project-snake exec backend-0 -- curl -s 10.44.0.22:3333 vault secret storage

Now we create the NP by copying and chaning an example from the k8s docs:

# 24_np.yaml apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata:name: np-backendnamespace: project-snake spec:podSelector:matchLabels:app: backendpolicyTypes:- Egress # policy is only about Egressegress:- # first ruleto: # first condition "to"- podSelector:matchLabels:app: db1ports: # second condition "port"- protocol: TCPport: 1111- # second ruleto: # first condition "to"- podSelector:matchLabels:app: db2ports: # second condition "port"- protocol: TCPport: 2222

The NP above has two rules with two conditions each, it can be read as:

allow outgoing traffic if:

(destination pod has label app=db1 AND port is 1111)

OR

(destination pod has label app=db2 AND port is 2222)

Wrong example

Now let’s shortly look at a wrong example:

# WRONG apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata:name: np-backendnamespace: project-snake spec:podSelector:matchLabels:app: backendpolicyTypes:- Egressegress:- # first ruleto: # first condition "to"- podSelector: # first "to" possibilitymatchLabels:app: db1- podSelector: # second "to" possibilitymatchLabels:app: db2ports: # second condition "ports"- protocol: TCP # first "ports" possibilityport: 1111- protocol: TCP # second "ports" possibilityport: 2222

The NP above has one rule with two conditions and two condition-entries each, it can be read as:

allow outgoing traffic if:

(destination pod has label app=db1 OR destination pod has label app=db2)

AND

(destination port is 1111 OR destination port is 2222)

Using this NP it would still be possible for backend-* Pods to connect to db2-* Pods on port 1111 for example which should be forbidden.

Create NetworkPolicy

We create the correct NP:

k -f 24_np.yaml create

And test again:

? k -n project-snake exec backend-0 -- curl -s 10.44.0.25:1111 database one? k -n project-snake exec backend-0 -- curl -s 10.44.0.23:2222 database two? k -n project-snake exec backend-0 -- curl -s 10.44.0.22:3333 ^C

Also helpful to use kubectl describe on the NP to see how k8s has interpreted the policy.

Great, looking more secure. Task done.

Question 25 | Etcd Snapshot Save and Restore

Task weight: 8%

Use context: kubectl config use-context k8s-c3-CCCMake a backup of etcd running on cluster3-controlplane1 and save it on the controlplane node at /tmp/etcd-backup.db.Then create a Pod of your kind in the cluster.Finally restore the backup, confirm the cluster is still working and that the created Pod is no longer with us.

Answer:
Etcd Backup

First we log into the controlplane and try to create a snapshop of etcd:

? ssh cluster3-controlplane1 ? root@cluster3-controlplane1:~# ETCDCTL_API=3 etcdctl snapshot save /tmp/etcd-backup.db Error: rpc error: code = Unavailable desc = transport is closing But it fails because we need to authenticate ourselves. For the necessary information we can check the etc manifest:? root@cluster3-controlplane1:~# vim /etc/kubernetes/manifests/etcd.yaml

We only check the etcd.yaml for necessary information we don’t change it.

# /etc/kubernetes/manifests/etcd.yamlapiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:component: etcdtier: control-planename: etcdnamespace: kube-system spec:containers:- command:- etcd- --advertise-client-urls=https://192.168.100.31:2379- --cert-file=/etc/kubernetes/pki/etcd/server.crt # use- --client-cert-auth=true- --data-dir=/var/lib/etcd- --initial-advertise-peer-urls=https://192.168.100.31:2380- --initial-cluster=cluster3-controlplane1=https://192.168.100.31:2380- --key-file=/etc/kubernetes/pki/etcd/server.key # use- --listen-client-urls=https://127.0.0.1:2379,https://192.168.100.31:2379 # use- --listen-metrics-urls=http://127.0.0.1:2381- --listen-peer-urls=https://192.168.100.31:2380- --name=cluster3-controlplane1- --peer-cert-file=/etc/kubernetes/pki/etcd/peer.crt- --peer-client-cert-auth=true- --peer-key-file=/etc/kubernetes/pki/etcd/peer.key- --peer-trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crt # use- --snapshot-count=10000- --trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crtimage: k8s.gcr.io/etcd:3.3.15-0imagePullPolicy: IfNotPresentlivenessProbe:failureThreshold: 8httpGet:host: 127.0.0.1path: /healthport: 2381scheme: HTTPinitialDelaySeconds: 15timeoutSeconds: 15name: etcdresources: {}volumeMounts:- mountPath: /var/lib/etcdname: etcd-data- mountPath: /etc/kubernetes/pki/etcdname: etcd-certshostNetwork: truepriorityClassName: system-cluster-criticalvolumes:- hostPath:path: /etc/kubernetes/pki/etcdtype: DirectoryOrCreatename: etcd-certs- hostPath:path: /var/lib/etcd # importanttype: DirectoryOrCreatename: etcd-data status: {}

But we also know that the api-server is connecting to etcd, so we can check how its manifest is configured:

? root@cluster3-controlplane1:~# cat /etc/kubernetes/manifests/kube-apiserver.yaml | grep etcd- --etcd-cafile=/etc/kubernetes/pki/etcd/ca.crt- --etcd-certfile=/etc/kubernetes/pki/apiserver-etcd-client.crt- --etcd-keyfile=/etc/kubernetes/pki/apiserver-etcd-client.key- --etcd-servers=https://127.0.0.1:2379

We use the authentication information and pass it to etcdctl:

? root@cluster3-controlplane1:~# ETCDCTL_API=3 etcdctl snapshot save /tmp/etcd-backup.db \ --cacert /etc/kubernetes/pki/etcd/ca.crt \ --cert /etc/kubernetes/pki/etcd/server.crt \ --key /etc/kubernetes/pki/etcd/server.key Snapshot saved at /tmp/etcd-backup.db NOTE: Dont use snapshot status because it can alter the snapshot file and render it invalid

Etcd restore

Now create a Pod in the cluster and wait for it to be running:

? root@cluster3-controlplane1:~# kubectl run test --image=nginx pod/test created? root@cluster3-controlplane1:~# kubectl get pod -l run=test -w NAME READY STATUS RESTARTS AGE test 1/1 Running 0 60s NOTE: If you didn't solve questions 18 or 20 and cluster3 doesn't have a ready worker node then the created pod might stay in a Pending state. This is still ok for this task.

Next we stop all controlplane components:

root@cluster3-controlplane1:~# cd /etc/kubernetes/manifests/ root@cluster3-controlplane1:/etc/kubernetes/manifests# mv * .. root@cluster3-controlplane1:/etc/kubernetes/manifests# watch crictl ps

Now we restore the snapshot into a specific directory:

? root@cluster3-controlplane1:~# ETCDCTL_API=3 etcdctl snapshot restore /tmp/etcd-backup.db \ --data-dir /var/lib/etcd-backup \ --cacert /etc/kubernetes/pki/etcd/ca.crt \ --cert /etc/kubernetes/pki/etcd/server.crt \ --key /etc/kubernetes/pki/etcd/server.key 2020-09-04 16:50:19.650804 I | mvcc: restore compact to 9935 2020-09-04 16:50:19.659095 I | etcdserver/membership: added member 8e9e05c52164694d [http://localhost:2380] to cluster cdf818194e3a8c32 We could specify another host to make the backup from by using etcdctl --endpoints http://IP, but here we just use the default value which is: http://127.0.0.1:2379,http://127.0.0.1:4001.

The restored files are located at the new folder /var/lib/etcd-backup, now we have to tell etcd to use that directory:

? root@cluster3-controlplane1:~# vim /etc/kubernetes/etcd.yaml # /etc/kubernetes/etcd.yamlapiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:component: etcdtier: control-planename: etcdnamespace: kube-system spec: ...- mountPath: /etc/kubernetes/pki/etcdname: etcd-certshostNetwork: truepriorityClassName: system-cluster-criticalvolumes:- hostPath:path: /etc/kubernetes/pki/etcdtype: DirectoryOrCreatename: etcd-certs- hostPath:path: /var/lib/etcd-backup # changetype: DirectoryOrCreatename: etcd-data status: {}

Now we move all controlplane yaml again into the manifest directory. Give it some time (up to several minutes) for etcd to restart and for the api-server to be reachable again:

root@cluster3-controlplane1:/etc/kubernetes/manifests# mv ../*.yaml . root@cluster3-controlplane1:/etc/kubernetes/manifests# watch crictl ps

Then we check again for the Pod:

? root@cluster3-controlplane1:~# kubectl get pod -l run=test No resources found in default namespace.

Awesome, backup and restore worked as our pod is gone.

Extra Question 1 | Find Pods first to be terminated

Use context: kubectl config use-context k8s-c1-HCheck all available Pods in the Namespace project-c13 and find the names of those that would probably be terminated first if the nodes run out of resources (cpu or memory) to schedule all Pods. Write the Pod names into /opt/course/e1/pods-not-stable.txt.

Answer:

When available cpu or memory resources on the nodes reach their limit, Kubernetes will look for Pods that are using more resources than they requested. These will be the first candidates for termination. If some Pods containers have no resource requests/limits set, then by default those are considered to use more than requested.

Kubernetes assigns Quality of Service classes to Pods based on the defined resources and limits, read more here: https://kubernetes.io/docs/tasks/configure-pod-container/quality-service-pod

Hence we should look for Pods without resource requests defined, we can do this with a manual approach:

k -n project-c13 describe pod | less -p Requests # describe all pods and highlight Requests

Or we do:

k -n project-c13 describe pod | egrep "^(Name:| Requests:)" -A1

We see that the Pods of Deployment c13-3cc-runner-heavy don’t have any resources requests specified. Hence our answer would be:

# /opt/course/e1/pods-not-stable.txt c13-3cc-runner-heavy-65588d7d6-djtv9map c13-3cc-runner-heavy-65588d7d6-v8kf5map c13-3cc-runner-heavy-65588d7d6-wwpb4map o3db-0 o3db-1 # maybe not existing if already removed via previous scenario

To automate this process you could use jsonpath like this:

? k -n project-c13 get pod \-o jsonpath="{range .items[*]} {.metadata.name}{.spec.containers[*].resources}{'\n'}"c13-2x3-api-86784557bd-cgs8gmap[requests:map[cpu:50m memory:20Mi]]c13-2x3-api-86784557bd-lnxvjmap[requests:map[cpu:50m memory:20Mi]]c13-2x3-api-86784557bd-mnp77map[requests:map[cpu:50m memory:20Mi]]c13-2x3-web-769c989898-6hbgtmap[requests:map[cpu:50m memory:10Mi]]c13-2x3-web-769c989898-g57nqmap[requests:map[cpu:50m memory:10Mi]]c13-2x3-web-769c989898-hfd5vmap[requests:map[cpu:50m memory:10Mi]]c13-2x3-web-769c989898-jfx64map[requests:map[cpu:50m memory:10Mi]]c13-2x3-web-769c989898-r89mgmap[requests:map[cpu:50m memory:10Mi]]c13-2x3-web-769c989898-wtgxlmap[requests:map[cpu:50m memory:10Mi]]c13-3cc-runner-98c8b5469-dzqhrmap[requests:map[cpu:30m memory:10Mi]]c13-3cc-runner-98c8b5469-hbtdvmap[requests:map[cpu:30m memory:10Mi]]c13-3cc-runner-98c8b5469-n9lswmap[requests:map[cpu:30m memory:10Mi]]c13-3cc-runner-heavy-65588d7d6-djtv9map[]c13-3cc-runner-heavy-65588d7d6-v8kf5map[]c13-3cc-runner-heavy-65588d7d6-wwpb4map[]c13-3cc-web-675456bcd-glpq6map[requests:map[cpu:50m memory:10Mi]]c13-3cc-web-675456bcd-knlpxmap[requests:map[cpu:50m memory:10Mi]]c13-3cc-web-675456bcd-nfhp9map[requests:map[cpu:50m memory:10Mi]]c13-3cc-web-675456bcd-twn7mmap[requests:map[cpu:50m memory:10Mi]]o3db-0{}o3db-1{}

This lists all Pod names and their requests/limits, hence we see the three Pods without those defined.

Or we look for the Quality of Service classes:

? k get pods -n project-c13 \-o jsonpath="{range .items[*]}{.metadata.name} {.status.qosClass}{'\n'}" c13-2x3-api-86784557bd-cgs8g Burstable c13-2x3-api-86784557bd-lnxvj Burstable c13-2x3-api-86784557bd-mnp77 Burstable c13-2x3-web-769c989898-6hbgt Burstable c13-2x3-web-769c989898-g57nq Burstable c13-2x3-web-769c989898-hfd5v Burstable c13-2x3-web-769c989898-jfx64 Burstable c13-2x3-web-769c989898-r89mg Burstable c13-2x3-web-769c989898-wtgxl Burstable c13-3cc-runner-98c8b5469-dzqhr Burstable c13-3cc-runner-98c8b5469-hbtdv Burstable c13-3cc-runner-98c8b5469-n9lsw Burstable c13-3cc-runner-heavy-65588d7d6-djtv9 BestEffort c13-3cc-runner-heavy-65588d7d6-v8kf5 BestEffort c13-3cc-runner-heavy-65588d7d6-wwpb4 BestEffort c13-3cc-web-675456bcd-glpq6 Burstable c13-3cc-web-675456bcd-knlpx Burstable c13-3cc-web-675456bcd-nfhp9 Burstable c13-3cc-web-675456bcd-twn7m Burstable o3db-0 BestEffort o3db-1 BestEffort

Here we see three with BestEffort, which Pods get that don’t have any memory or cpu limits or requests defined.

A good practice is to always set resource requests and limits. If you don’t know the values your containers should have you can find this out using metric tools like Prometheus. You can also use kubectl top pod or even kubectl exec into the container and use top and similar tools.

Extra Question 2 | Curl Manually Contact API

Use context: kubectl config use-context k8s-c1-HThere is an existing ServiceAccount secret-reader in Namespace project-hamster. Create a Pod of image curlimages/curl:7.65.3 named tmp-api-contact which uses this ServiceAccount. Make sure the container keeps running.Exec into the Pod and use curl to access the Kubernetes Api of that cluster manually, listing all available secrets. You can ignore insecure https connection. Write the command(s) for this into file /opt/course/e4/list-secrets.sh.

Answer:

https://kubernetes.io/docs/tasks/run-application/access-api-from-pod

It’s important to understand how the Kubernetes API works. For this it helps connecting to the api manually, for example using curl. You can find information fast by search in the Kubernetes docs for “curl api” for example.

First we create our Pod:

k run tmp-api-contact --image=curlimages/curl:7.65.3 $do --command > e2.yaml -- sh -c 'sleep 1d'

Add the service account name and Namespace:

# e2.yaml apiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:run: tmp-api-contactname: tmp-api-contactnamespace: project-hamster # add spec:serviceAccountName: secret-reader # addcontainers:- command:- sh- -c- sleep 1dimage: curlimages/curl:7.65.3name: tmp-api-contactresources: {}dnsPolicy: ClusterFirstrestartPolicy: Always status: {}

Then run and exec into:

k -f 6.yaml create k -n project-hamster exec tmp-api-contact -it -- sh

Once on the container we can try to connect to the api using curl, the api is usually available via the Service named kubernetes in Namespace default (You should know how dns resolution works across Namespaces.). Else we can find the endpoint IP via environment variables running env.

So now we can do:

curl https://kubernetes.default curl -k https://kubernetes.default # ignore insecure as allowed in ticket description curl -k https://kubernetes.default/api/v1/secrets # should show Forbidden 403

The last command shows 403 forbidden, this is because we are not passing any authorisation information with us. The Kubernetes Api Server thinks we are connecting as system:anonymous. We want to change this and connect using the Pods ServiceAccount named secret-reader.

We find the the token in the mounted folder at /var/run/secrets/kubernetes.io/serviceaccount, so we do:

? TOKEN=$(cat /var/run/secrets/kubernetes.io/serviceaccount/token) ? curl -k https://kubernetes.default/api/v1/secrets -H "Authorization: Bearer ${TOKEN}"% Total % Received % Xferd Average Speed Time Time Time CurrentDload Upload Total Spent Left Speed0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0{"kind": "SecretList","apiVersion": "v1","metadata": {"selfLink": "/api/v1/secrets","resourceVersion": "10697"},"items": [{"metadata": {"name": "default-token-5zjbd","namespace": "default","selfLink": "/api/v1/namespaces/default/secrets/default-token-5zjbd","uid": "315dbfd9-d235-482b-8bfc-c6167e7c1461","resourceVersion": "342",...

Now we’re able to list all Secrets, registering as the ServiceAccount secret-reader under which our Pod is running.

To use encrypted https connection we can run:

CACERT=/var/run/secrets/kubernetes.io/serviceaccount/ca.crt curl --cacert ${CACERT} https://kubernetes.default/api/v1/secrets -H "Authorization: Bearer ${TOKEN}"

For troubleshooting we could also check if the ServiceAccount is actually able to list Secrets using:

? k auth can-i get secret --as system:serviceaccount:project-hamster:secret-readeryes

Finally write the commands into the requested location:

# /opt/course/e4/list-secrets.shTOKEN=$(cat /var/run/secrets/kubernetes.io/serviceaccount/token) curl -k https://kubernetes.default/api/v1/secrets -H "Authorization: Bearer ${TOKEN}"

Preview Question 1

Use context: kubectl config use-context k8s-c2-ACThe cluster admin asked you to find out the following information about etcd running on cluster2-controlplane1:Server private key locationServer certificate expiration dateIs client certificate authentication enabledWrite these information into /opt/course/p1/etcd-info.txt

Finally you’re asked to save an etcd snapshot at /etc/etcd-snapshot.db on cluster2-controlplane1 and display its status.

Answer:
Find out etcd information
Let’s check the nodes:

? k get node NAME STATUS ROLES AGE VERSION cluster2-controlplane1 Ready control-plane 89m v1.23.1 cluster2-node1 Ready <none> 87m v1.23.1? ssh cluster2-controlplane1

First we check how etcd is setup in this cluster:

? root@cluster2-controlplane1:~# kubectl -n kube-system get pod NAME READY STATUS RESTARTS AGE coredns-66bff467f8-k8f48 1/1 Running 0 26h coredns-66bff467f8-rn8tr 1/1 Running 0 26h etcd-cluster2-controlplane1 1/1 Running 0 26h kube-apiserver-cluster2-controlplane1 1/1 Running 0 26h kube-controller-manager-cluster2-controlplane1 1/1 Running 0 26h kube-proxy-qthfg 1/1 Running 0 25h kube-proxy-z55lp 1/1 Running 0 26h kube-scheduler-cluster2-controlplane1 1/1 Running 1 26h weave-net-cqdvt 2/2 Running 0 26h weave-net-dxzgh 2/2 Running 1 25h

We see it’s running as a Pod, more specific a static Pod. So we check for the default kubelet directory for static manifests:

? root@cluster2-controlplane1:~# find /etc/kubernetes/manifests/ /etc/kubernetes/manifests/ /etc/kubernetes/manifests/kube-controller-manager.yaml /etc/kubernetes/manifests/kube-apiserver.yaml /etc/kubernetes/manifests/etcd.yaml /etc/kubernetes/manifests/kube-scheduler.yaml? root@cluster2-controlplane1:~# vim /etc/kubernetes/manifests/etcd.yaml

So we look at the yaml and the parameters with which etcd is started:

# /etc/kubernetes/manifests/etcd.yamlapiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:component: etcdtier: control-planename: etcdnamespace: kube-system spec:containers:- command:- etcd- --advertise-client-urls=https://192.168.102.11:2379- --cert-file=/etc/kubernetes/pki/etcd/server.crt # server certificate- --client-cert-auth=true # enabled- --data-dir=/var/lib/etcd- --initial-advertise-peer-urls=https://192.168.102.11:2380- --initial-cluster=cluster2-controlplane1=https://192.168.102.11:2380- --key-file=/etc/kubernetes/pki/etcd/server.key # server private key- --listen-client-urls=https://127.0.0.1:2379,https://192.168.102.11:2379- --listen-metrics-urls=http://127.0.0.1:2381- --listen-peer-urls=https://192.168.102.11:2380- --name=cluster2-controlplane1- --peer-cert-file=/etc/kubernetes/pki/etcd/peer.crt- --peer-client-cert-auth=true- --peer-key-file=/etc/kubernetes/pki/etcd/peer.key- --peer-trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crt- --snapshot-count=10000- --trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crt

We see that client authentication is enabled and also the requested path to the server private key, now let’s find out the expiration of the server certificate:

? root@cluster2-controlplane1:~# openssl x509 -noout -text -in /etc/kubernetes/pki/etcd/server.crt | grep Validity -A2ValidityNot Before: Sep 13 13:01:31 2021 GMTNot After : Sep 13 13:01:31 2022 GMT

There we have it. Let’s write the information into the requested file:

# /opt/course/p1/etcd-info.txtServer private key location: /etc/kubernetes/pki/etcd/server.key Server certificate expiration date: Sep 13 13:01:31 2022 GMT Is client certificate authentication enabled: yes

Create etcd snapshot
First we try:

ETCDCTL_API=3 etcdctl snapshot save /etc/etcd-snapshot.db

We get the endpoint also from the yaml. But we need to specify more parameters, all of which we can find the yaml declaration above:

ETCDCTL_API=3 etcdctl snapshot save /etc/etcd-snapshot.db \ --cacert /etc/kubernetes/pki/etcd/ca.crt \ --cert /etc/kubernetes/pki/etcd/server.crt \ --key /etc/kubernetes/pki/etcd/server.key

This worked. Now we can output the status of the backup file:

? root@cluster2-controlplane1:~# ETCDCTL_API=3 etcdctl snapshot status /etc/etcd-snapshot.db 4d4e953, 7213, 1291, 2.7 MB The status shows:Hash: 4d4e953Revision: 7213Total Keys: 1291Total Size: 2.7 MB

Preview Question 2

Use context: kubectl config use-context k8s-c1-HYou're asked to confirm that kube-proxy is running correctly on all nodes. For this perform the following in Namespace project-hamster:Create a new Pod named p2-pod with two containers, one of image nginx:1.21.3-alpine and one of image busybox:1.31. Make sure the busybox container keeps running for some time. Create a new Service named p2-service which exposes that Pod internally in the cluster on port 3000->80. Find the kube-proxy container on all nodes cluster1-controlplane1, cluster1-node1 and cluster1-node2 and make sure that it's using iptables. Use command crictl for this. Write the iptables rules of all nodes belonging the created Service p2-service into file /opt/course/p2/iptables.txt. Finally delete the Service and confirm that the iptables rules are gone from all nodes.

Answer:
Create the Pod
First we create the Pod:

# check out export statement on top which allows us to use $dok run p2-pod --image=nginx:1.21.3-alpine $do > p2.yaml

Next we add the requested second container:

# p2.yaml apiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:run: p2-podname: p2-podnamespace: project-hamster # add spec:containers:- image: nginx:1.21.3-alpinename: p2-pod- image: busybox:1.31 # addname: c2 # addcommand: ["sh", "-c", "sleep 1d"] # addresources: {}dnsPolicy: ClusterFirstrestartPolicy: Always status: {}

And we create the Pod:

k -f p2.yaml create

Create the Service

Next we create the Service:

k -n project-hamster expose pod p2-pod --name p2-service --port 3000 --target-port 80

This will create a yaml like:

apiVersion: v1 kind: Service metadata:creationTimestamp: "2020-04-30T20:58:14Z"labels:run: p2-podmanagedFields: ...operation: Updatetime: "2020-04-30T20:58:14Z"name: p2-servicenamespace: project-hamsterresourceVersion: "11071"selfLink: /api/v1/namespaces/project-hamster/services/p2-serviceuid: 2a1c0842-7fb6-4e94-8cdb-1602a3b1e7d2 spec:clusterIP: 10.97.45.18ports:- port: 3000protocol: TCPtargetPort: 80selector:run: p2-podsessionAffinity: Nonetype: ClusterIP status:loadBalancer: {}

We should confirm Pods and Services are connected, hence the Service should have Endpoints.

k -n project-hamster get pod,svc,ep

Confirm kube-proxy is running and is using iptables

First we get nodes in the cluster:

? k get nodeNAME STATUS ROLES AGE VERSION cluster1-controlplane1 Ready control-plane 98m v1.23.1 cluster1-node1 Ready <none> 96m v1.23.1 cluster1-node2 Ready <none> 95m v1.23.1

The idea here is to log into every node, find the kube-proxy container and check its logs:

? ssh cluster1-controlplane1 ? root@cluster1-controlplane1$ crictl ps | grep kube-proxy 27b6a18c0f89c 36c4ebbc9d979 3 hours ago Running kube-proxy? root@cluster1-controlplane1~# crictl logs 27b6a18c0f89c ... I0913 12:53:03.096620 1 server_others.go:212] Using iptables Proxier. ... This should be repeated on every node and result in the same output Using iptables Proxier.

Check kube-proxy is creating iptables rules

Now we check the iptables rules on every node first manually:

? ssh cluster1-controlplane1 iptables-save | grep p2-service -A KUBE-SEP-6U447UXLLQIKP7BB -s 10.44.0.20/32 -m comment --comment "project-hamster/p2-service:" -j KUBE-MARK-MASQ -A KUBE-SEP-6U447UXLLQIKP7BB -p tcp -m comment --comment "project-hamster/p2-service:" -m tcp -j DNAT --to-destination 10.44.0.20:80 -A KUBE-SERVICES ! -s 10.244.0.0/16 -d 10.97.45.18/32 -p tcp -m comment --comment "project-hamster/p2-service: cluster IP" -m tcp --dport 3000 -j KUBE-MARK-MASQ -A KUBE-SERVICES -d 10.97.45.18/32 -p tcp -m comment --comment "project-hamster/p2-service: cluster IP" -m tcp --dport 3000 -j KUBE-SVC-2A6FNMCK6FDH7PJH -A KUBE-SVC-2A6FNMCK6FDH7PJH -m comment --comment "project-hamster/p2-service:" -j KUBE-SEP-6U447UXLLQIKP7BB? ssh cluster1-node1 iptables-save | grep p2-service -A KUBE-SEP-6U447UXLLQIKP7BB -s 10.44.0.20/32 -m comment --comment "project-hamster/p2-service:" -j KUBE-MARK-MASQ -A KUBE-SEP-6U447UXLLQIKP7BB -p tcp -m comment --comment "project-hamster/p2-service:" -m tcp -j DNAT --to-destination 10.44.0.20:80 -A KUBE-SERVICES ! -s 10.244.0.0/16 -d 10.97.45.18/32 -p tcp -m comment --comment "project-hamster/p2-service: cluster IP" -m tcp --dport 3000 -j KUBE-MARK-MASQ -A KUBE-SERVICES -d 10.97.45.18/32 -p tcp -m comment --comment "project-hamster/p2-service: cluster IP" -m tcp --dport 3000 -j KUBE-SVC-2A6FNMCK6FDH7PJH -A KUBE-SVC-2A6FNMCK6FDH7PJH -m comment --comment "project-hamster/p2-service:" -j KUBE-SEP-6U447UXLLQIKP7BB? ssh cluster1-node2 iptables-save | grep p2-service -A KUBE-SEP-6U447UXLLQIKP7BB -s 10.44.0.20/32 -m comment --comment "project-hamster/p2-service:" -j KUBE-MARK-MASQ -A KUBE-SEP-6U447UXLLQIKP7BB -p tcp -m comment --comment "project-hamster/p2-service:" -m tcp -j DNAT --to-destination 10.44.0.20:80 -A KUBE-SERVICES ! -s 10.244.0.0/16 -d 10.97.45.18/32 -p tcp -m comment --comment "project-hamster/p2-service: cluster IP" -m tcp --dport 3000 -j KUBE-MARK-MASQ -A KUBE-SERVICES -d 10.97.45.18/32 -p tcp -m comment --comment "project-hamster/p2-service: cluster IP" -m tcp --dport 3000 -j KUBE-SVC-2A6FNMCK6FDH7PJH -A KUBE-SVC-2A6FNMCK6FDH7PJH -m comment --comment "project-hamster/p2-service:" -j KUBE-SEP-6U447UXLLQIKP7BB

Great. Now let’s write these logs into the requested file:

? ssh cluster1-controlplane1 iptables-save | grep p2-service >> /opt/course/p2/iptables.txt ? ssh cluster1-node1 iptables-save | grep p2-service >> /opt/course/p2/iptables.txt ? ssh cluster1-node2 iptables-save | grep p2-service >> /opt/course/p2/iptables.txt

Delete the Service and confirm iptables rules are gone

Delete the Service:

k -n project-hamster delete svc p2-service

And confirm the iptables rules are gone:

? ssh cluster1-controlplane1 iptables-save | grep p2-service ? ssh cluster1-node1 iptables-save | grep p2-service ? ssh cluster1-node2 iptables-save | grep p2-service

Done.

Kubernetes Services are implemented using iptables rules (with default config) on all nodes. Every time a Service has been altered, created, deleted or Endpoints of a Service have changed, the kube-apiserver contacts every node’s kube-proxy to update the iptables rules according to the current state.

Preview Question 3

Use context: kubectl config use-context k8s-c2-ACCreate a Pod named check-ip in Namespace default using image httpd:2.4.41-alpine. Expose it on port 80 as a ClusterIP Service named check-ip-service. Remember/output the IP of that Service.Change the Service CIDR to 11.96.0.0/12 for the cluster.Then create a second Service named check-ip-service2 pointing to the same Pod to check if your settings did take effect. Finally check if the IP of the first Service has changed.

Answer:

Let’s create the Pod and expose it:

k run check-ip --image=httpd:2.4.41-alpine k expose pod check-ip --name check-ip-service --port 80

And check the Pod and Service ips:

? k get svc,ep -l run=check-ip NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/check-ip-service ClusterIP 10.104.3.45 <none> 80/TCP 8s NAME ENDPOINTS AGE endpoints/check-ip-service 10.44.0.3:80 7s

Now we change the Service CIDR on the kube-apiserver:

? ssh cluster2-controlplane1 ? root@cluster2-controlplane1:~# vim /etc/kubernetes/manifests/kube-apiserver.yaml # /etc/kubernetes/manifests/kube-apiserver.yamlapiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:component: kube-apiservertier: control-planename: kube-apiservernamespace: kube-system spec:containers:- command:- kube-apiserver- --advertise-address=192.168.100.21...- --service-account-key-file=/etc/kubernetes/pki/sa.pub- --service-cluster-ip-range=11.96.0.0/12 # change- --tls-cert-file=/etc/kubernetes/pki/apiserver.crt- --tls-private-key-file=/etc/kubernetes/pki/apiserver.key ...

Give it a bit for the kube-apiserver and controller-manager to restart

Wait for the api to be up again:

? root@cluster2-controlplane1:~# kubectl -n kube-system get pod | grep api kube-apiserver-cluster2-controlplane1 1/1 Running 0 49s

Now we do the same for the controller manager:

? root@cluster2-controlplane1:~# vim /etc/kubernetes/manifests/kube-controller-manager.yaml # /etc/kubernetes/manifests/kube-controller-manager.yamlapiVersion: v1 kind: Pod metadata:creationTimestamp: nulllabels:component: kube-controller-managertier: control-planename: kube-controller-managernamespace: kube-system spec:containers:- command:- kube-controller-manager- --allocate-node-cidrs=true- --authentication-kubeconfig=/etc/kubernetes/controller-manager.conf- --authorization-kubeconfig=/etc/kubernetes/controller-manager.conf- --bind-address=127.0.0.1- --client-ca-file=/etc/kubernetes/pki/ca.crt- --cluster-cidr=10.244.0.0/16- --cluster-name=kubernetes- --cluster-signing-cert-file=/etc/kubernetes/pki/ca.crt- --cluster-signing-key-file=/etc/kubernetes/pki/ca.key- --controllers=*,bootstrapsigner,tokencleaner- --kubeconfig=/etc/kubernetes/controller-manager.conf- --leader-elect=true- --node-cidr-mask-size=24- --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt- --root-ca-file=/etc/kubernetes/pki/ca.crt- --service-account-private-key-file=/etc/kubernetes/pki/sa.key- --service-cluster-ip-range=11.96.0.0/12 # change- --use-service-account-credentials=true

Give it a bit for the scheduler to restart.

We can check if it was restarted using crictl:

? root@cluster2-controlplane1:~# crictl ps | grep scheduler 3d258934b9fd6 aca5ededae9c8 About a minute ago Running kube-scheduler ...

Checking our existing Pod and Service again:

? k get pod,svc -l run=check-ip NAME READY STATUS RESTARTS AGE pod/check-ip 1/1 Running 0 21mNAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/check-ip-service ClusterIP 10.99.32.177 <none> 80/TCP 21m

Nothing changed so far. Now we create another Service like before:

k expose pod check-ip --name check-ip-service2 --port 80

And check again:

? k get svc,ep -l run=check-ip NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/check-ip-service ClusterIP 10.109.222.111 <none> 80/TCP 8m service/check-ip-service2 ClusterIP 11.111.108.194 <none> 80/TCP 6m32sNAME ENDPOINTS AGE endpoints/check-ip-service 10.44.0.1:80 8m endpoints/check-ip-service2 10.44.0.1:80 6m13s

There we go, the new Service got an ip of the new specified range assigned. We also see that both Services have our Pod as endpoint.

CKA Tips Kubernetes 1.26

In this section we’ll provide some tips on how to handle the CKA exam and browser terminal.

Knowledge

Study all topics as proposed in the curriculum till you feel comfortable with all.

General

Study all topics as proposed in the curriculum till you feel comfortable with all Do 1 or 2 test session with this CKA Simulator. Understand the solutions and maybe try out other ways to achieve the same thing. Setup your aliases, be fast and breath kubectl The majority of tasks in the CKA will also be around creating Kubernetes resources, like it's tested in the CKAD. So preparing a bit for the CKAD can't hurt. Learn and Study the in-browser scenarios on https://killercoda.com/killer-shell-cka (and maybe for CKAD https://killercoda.com/killer-shell-ckad) Imagine and create your own scenarios to solve

Components

Understanding Kubernetes components and being able to fix and investigate clusters: https://kubernetes.io/docs/tasks/debug-application-cluster/debug-cluster Know advanced scheduling: https://kubernetes.io/docs/concepts/scheduling/kube-scheduler When you have to fix a component (like kubelet) in one cluster, just check how it's setup on another node in the same or even another cluster. You can copy config files over etc If you like you can look at Kubernetes The Hard Way once. But it's NOT necessary to do, the CKA is not that complex. But KTHW helps understanding the concepts You should install your own cluster using kubeadm (one controlplane, one worker) in a VM or using a cloud provider and investigate the components Know how to use Kubeadm to for example add nodes to a cluster Know how to create an Ingress resources Know how to snapshot/restore ETCD from another machine

CKA Preparation

Read the Curriculum

https://github.com/cncf/curriculum

Read the Handbook

https://docs.linuxfoundation.org/tc-docs/certification/lf-candidate-handbook

Read the important tips

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

Read the FAQ：

https://docs.linuxfoundation.org/tc-docs/certification/faq-cka-ckad

Kubernetes documentation

Get familiar with the Kubernetes documentation and be able to use the search. Allowed links are:

https://kubernetes.io/docs https://kubernetes.io/blog https://helm.sh/docsNOTE: Verify the list here

The Test Environment / Browser Terminal

You’ll be provided with a browser terminal which uses Ubuntu 20. The standard shells included with a minimal install of Ubuntu 20 will be available, including bash.

Laggin

There could be some lagging, definitely make sure you are using a good internet connection because your webcam and screen are uploading all the time.

Kubectl autocompletion and commands

Autocompletion is configured by default, as well as the k alias source and others:

kubectl with k alias and Bash autocompletion

yq and jqfor YAML/JSON processing

tmux for terminal multiplexing

curl and wget for testing web services

man and man pages for further documentation

Copy & Paste

There could be issues copying text (like pod names) from the left task information into the terminal. Some suggested to “hard” hit or long hold Cmd/Ctrl+C a few times to take action. Apart from that copy and paste should just work like in normal terminals.

Percentages and Score

There are 15-20 questions in the exam and 100% of total percentage to reach. Each questions shows the % it gives if you solve it. Your results will be automatically checked according to the handbook. If you don’t agree with the results you can request a review by contacting the Linux Foundation support.

Notepad & Skipping Questions

You have access to a simple notepad in the browser which can be used for storing any kind of plain text. It makes sense to use this for saving skipped question numbers and their percentages. This way it’s possible to move some questions to the end. It might make sense to skip 2% or 3% questions and go directly to higher ones.

Contexts

You’ll receive access to various different clusters and resources in each. They provide you the exact command you need to run to connect to another cluster/context. But you should be comfortable working in different namespaces with kubectl.

PSI Bridge

Starting with PSI Bridge:

The exam will now be taken using the PSI Secure Browser, which can be downloaded using the newest versions of Microsoft Edge, Safari, Chrome, or Firefox Multiple monitors will no longer be permitted Use of personal bookmarks will no longer be permitted

The new ExamUI includes improved features such as:

A remote desktop configured with the tools and software needed to complete the tasks A timer that displays the actual time remaining (in minutes) and provides an alert with 30, 15, or 5 minute remaining The content panel remains the same (presented on the Left Hand Side of the ExamUI)

Read more here.

Browser Terminal Setup

It should be considered to spend ~1 minute in the beginning to setup your terminal. In the real exam the vast majority of questions will be done from the main terminal. For few you might need to ssh into another machine. Just be aware that configurations to your shell will not be transferred in this case.
Minimal Setup

Alias

The alias k for kubectl will already be configured together with autocompletion. In case not you can configure it using this link.

Vim

The following settings will already be configured in your real exam environment in ~/.vimrc. But it can never hurt to be able to type these down:

set tabstop=2set expandtabset shiftwidth=2

The expandtab make sure to use spaces for tabs. Memorize these and just type them down. You can’t have any written notes with commands on your desktop etc.
Optional Setup

Fast dry-run output

export do="--dry-run=client -o yaml"

This way you can just run k run pod1 --image=nginx $do. Short for “dry output”, but use whatever name you like.

Fast pod delete

export now="--force --grace-period 0"

This way you can run k delete pod1 $now and don’t have to wait for ~30 seconds termination time.

Persist bash settings

You can store aliases and other setup in ~/.bashrc if you’re planning on using different shells or tmux.

Alias Namespace

In addition you could define an alias like:

alias kn='kubectl config set-context --current --namespace '

Which allows you to define the default namespace of the current context. Then once you switch a context or namespace you can just run:

kn default # set default to defaultkn my-namespace # set default to my-namespace

But only do this if you used it before and are comfortable doing so. Else you need to specify the namespace for every call, which is also fine:

k -n my-namespace get allk -n my-namespace get pod

…

Be fast

Use the history command to reuse already entered commands or use even faster history search through Ctrl r .

If a command takes some time to execute, like sometimes kubectl delete pod x. You can put a task in the background using Ctrl z and pull it back into foreground running command fg.

You can delete pods fast with:

k delete pod x --grace-period 0 --force

k delete pod x $now # if export from above is configured

Vim

Be great with vim.

toggle vim line numbers

When in vim you can press Esc and type :set number or :set nonumber followed by Enter to toggle line numbers. This can be useful when finding syntax errors based on line - but can be bad when wanting to mark&copy by mouse. You can also just jump to a line number with Esc :22 + Enter.

copy&paste

Get used to copy/paste/cut with vim:

Mark lines: Esc+V (then arrow keys)

Copy marked lines: y

Cut marked lines: d

Past lines: p or P

Indent multiple lines

To indent multiple lines press Esc and type :set shiftwidth=2. First mark multiple lines using Shift v and the up/down keys. Then to indent the marked lines press > or <. You can then press . to repeat the action.

Split terminal screen

By default tmux is installed and can be used to split your one terminal into multiple. But just do this if you know your shit, because scrolling is different and copy&pasting might be weird.

https://www.hamvocke.com/blog/a-quick-and-easy-guide-to-tmux

總結

以上是生活随笔為你收集整理的CKA-1.26 模拟试题的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。