报名参加CKA考试后有两次模拟考试机会，题目难度比真实考试难度要大，这里记录下原题目和答案
CKA Simulator Kubernetes 1.22
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 get pod x $do
export now="--force --grace-period 0" # k delete pod x $nowVim To make vim use 2 spaces for a tab edit ~/.vimrc to contain:
set tabstop=2
set expandtab
set shiftwidth=2More 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 # copy manually
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/contextsThe content should then look like:
# /opt/course/1/contexts
k8s-c1-H
k8s-c2-AC
k8s-c3-CCCNext 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-HAnd 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-HIn 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 Master Node
Task weight: 3%
Use context: kubectl config use-context k8s-c1-H
Create 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 master node, do not add new labels any nodes.
Shortly write the reason on why Pods are by default not scheduled on master nodes into /opt/course/2/master_schedule_reason.
Answer: First we find the master node(s) and their taints:
k get node # find master node
k describe node cluster1-master1 | grep Taint # get master node taints
# -A 是显示匹配后和它后面的n行
# -B 是显示匹配行和它前面的n行。
# -C 是匹配行和它前后各n行。
k describe node cluster1-master1 | grep Labels -A 10 # get master node labels
k get node cluster1-master1 --show-labels # OR: get master node labelsNext 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.yamlvim 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: null
labels:
run: pod1
name: pod1
spec:
containers:
- image: httpd:2.4.41-alpine
name: pod1-container # change
resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Always
tolerations: # add
- effect: NoSchedule # add
key: node-role.kubernetes.io/master # add
nodeSelector: # add
node-role.kubernetes.io/master: "" # add
# kubernetes.io/hostname: "cluster1-master1"
status: {}Important here to add the toleration for running on master nodes, but also the nodeSelector to make sure it only runs on master nodes.
If we only specify a toleration the Pod can be scheduled on master 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-master1 <none>Finally the short reason why Pods are not scheduled on master nodes by default:
# /opt/course/2/master_schedule_reason
master nodes usually have a taint definedQuestion 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. Record the action.
Answer: If we check the Pods we see two replicas:
➜ k -n project-c13 get pod | grep o3db
o3db-0 1/1 Running 0 52s
o3db-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 o3db
statefulset.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 o3db
o3db-0 1/1 Running 0 3m29s app=nginx,controller-revision-hash=o3db-5fbd4bb9cc,statefulset.kubernetes.io/pod-name=o3db-0
o3db-1 1/1 Running 0 3m19s app=nginx,controller-revision-hash=o3db-5fbd4bb9cc,statefulset.kubernetes.io/pod-name=o3db-1To fulfil the task we simply run:
➜ k -n project-c13 scale sts o3db --replicas 1 --record
statefulset.apps/o3db scaled
➜ k -n project-c13 get sts o3db
NAME READY AGE
o3db 1/1 4m39sThe --record created an annotation:
➜ k -n project-c13 describe sts o3db
Name: o3db
Namespace: project-c13
CreationTimestamp: Sun, 20 Sep 2020 14:47:57 +0000
Selector: app=nginx
Labels: <none>
Annotations: kubernetes.io/change-cause: kubectl scale sts o3db --namespace=project-c13 --replicas=1 --record=true
Replicas: 1 desired | 1 totalC13 Management is happy again.
Question 4 | Pod Ready if Service is reachable
Task weight: 4%
Use context: kubectl config use-context k8s-c1-H
Do 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 runs 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
vim 4_pod1.yamlNext perform the necessary additions manually:
# 4_pod1.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: ready-if-service-ready
name: ready-if-service-ready
spec:
containers:
- image: nginx:1.16.1-alpine
name: ready-if-service-ready
resources: {}
livenessProbe: # add from here
exec:
command:
- 'true'
readinessProbe:
exec:
command:
- sh
- -c
- 'wget -T2 -O- http://service-am-i-ready:80' # to here
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}Then create the Pod:
k -f 4_pod1.yaml create And confirm its 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 7sWe can also check the reason for this using describe:
➜ k describe pod ready-if-service-ready
...
Warning Unhealthy 18s kubelet, cluster1-worker1 Readiness probe failed: Connecting to service-am-i-ready:80 (10.109.194.234:80)
wget: download timed outNow 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-ready
k get ep # also possibleWhich 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 53sLook at these Pods coworking together!
Question 5 | Kubectl sorting
Task weight: 1%
Use context: kubectl config use-context k8s-c1-H
There 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.creationTimestampAnd to execute:
➜ sh /opt/course/5/find_pods.sh
NAMESPACE NAME ... AGE
kube-system kube-scheduler-cluster1-master1 ... 63m
kube-system etcd-cluster1-master1 ... 63m
kube-system kube-apiserver-cluster1-master1 ... 63m
kube-system kube-controller-manager-cluster1-master1 ... 63m
...For the second command:
# /opt/course/5/find_pods_uid.sh
kubectl get pod -A --sort-by=.metadata.uidAnd 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 ... 63mQuestion 6 | Storage, PV, PVC, Pod volume
Task weight: 8%
Use context: kubectl config use-context k8s-c1-H
Create 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 vim 6_pv.yaml 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: 2Gi
accessModes:
- ReadWriteOnce
hostPath:
path: "/Volumes/Data"Then create it:
k -f 6_pv.yaml create Next the PersistentVolumeClaim:
vim 6_pvc.yaml Find an example from https://kubernetes.io/docs and alter it:
# 6_pvc.yaml
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: safari-pvc
namespace: project-tiger
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 2Gik -f 6_pvc.yaml create And check that both have the status Bound:
➜ k -n project-tiger get pv,pvc
NAME 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.yamlvim 6_dep.yaml Alter the yaml to mount the volume:
# 6_dep.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
creationTimestamp: null
labels:
app: safari
name: safari
namespace: project-tiger
spec:
replicas: 1
selector:
matchLabels:
app: safari
strategy: {}
template:
metadata:
creationTimestamp: null
labels:
app: safari
spec:
volumes: # add
- name: data # add
persistentVolumeClaim: # add
claimName: safari-pvc # add
containers:
- image: httpd:2.4.41-alpine
name: container
volumeMounts: # add
- name: data # add
mountPath: /tmp/safari-data # addk -f 6_dep.yaml create
We can confirm its 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-H
The metrics-server hasn't been installed yet in the cluster, but it's something that should be done soon. Your college would already like to know the kubectl commands to:
show node resource usage show Pod 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:
Display 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 nodes
pod Display Resource (CPU/Memory/Storage) usage of podsWe see that the metrics server is not configured yet:
error: Metrics API not availableBut we trust the kubectl documentation and create the first file:
# /opt/course/7/node.sh
kubectl top nodeFor 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=trueQuestion 8 | Get Master Information
Task weight: 2%
Use context: kubectl config use-context k8s-c1-H
Ssh into the master node with ssh cluster1-master1. Check how the master components kubelet, kube-apiserver, kube-scheduler, kube-controller-manager and etcd are started/installed on the master node.
Also find out the name of the DNS application and how it's started/installed on the master node.
Write your findings into file /opt/course/8/master-components.txt. The file should be structured like:
# /opt/course/8/master-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, podAnswer: We could start by finding processes of the requested components, especially the kubelet at first:
➜ ssh cluster1-master1
root@cluster1-master1:~# ps aux | grep kubelet # shows kubelet processWe can see which components are controlled via systemd looking at /etc/systemd/system directory:
➜ root@cluster1-master1:~# 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-master1:~# find /etc/systemd/system/ | grep etcdThis 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-master1:~# find /etc/kubernetes/manifests/
/etc/kubernetes/manifests/
/etc/kubernetes/manifests/kube-controller-manager.yaml
/etc/kubernetes/manifests/etcd.yaml
/etc/kubernetes/manifests/kube-scheduler-special.yaml
/etc/kubernetes/manifests/kube-apiserver.yaml
/etc/kubernetes/manifests/kube-scheduler.yaml
cat kube-scheduler-special.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
name: kube-scheduler-special
labels:
component: kube-scheduler
tier: control-plane
namespace: kube-system
spec:
containers:
- command:
- kube-scheduler
- --authentication-kubeconfig=/etc/kubernetes/scheduler.conf
- --authorization-kubeconfig=/etc/kubernetes/scheduler.conf
- --bind-address=127.0.0.1
- --port=7776
- --secure-port=7777
- --kubeconfig=/etc/kubernetes/kube-scheduler.conf
- --leader-elect=false
- --scheduler-name=kube-scheduler-special
- --this-is-no-parameter=what-the-hell
image: k8s.gcr.io/kube-scheduler:v1.22.1
imagePullPolicy: IfNotPresent
name: kube-scheduler-special
resources:
requests:
cpu: 100m
volumeMounts:
- mountPath: /etc/kubernetes/scheduler.conf
name: kubeconfig
readOnly: true
hostNetwork: true
priorityClassName: system-cluster-critical
volumes:
- hostPath:
path: /etc/kubernetes/scheduler.conf
type: FileOrCreate
name: kubeconfig
status: {}(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 master services are setup as static Pods. There also seems to be a second scheduler kube-scheduler-special existing.
Actually, let's check all Pods running on in the kube-system Namespace on the master node:
➜ root@cluster1-master1:~# kubectl -n kube-system get pod -o wide | grep master1
coredns-5644d7b6d9-c4f68 1/1 Running ... cluster1-master1
coredns-5644d7b6d9-t84sc 1/1 Running ... cluster1-master1
etcd-cluster1-master1 1/1 Running ... cluster1-master1
kube-apiserver-cluster1-master1 1/1 Running ... cluster1-master1
kube-controller-manager-cluster1-master1 1/1 Running ... cluster1-master1
kube-proxy-q955p 1/1 Running ... cluster1-master1
kube-scheduler-cluster1-master1 1/1 Running ... cluster1-master1
kube-scheduler-special-cluster1-master1 0/1 CrashLoopBackOff ... cluster1-master1
weave-net-mwj47 2/2 Running ... cluster1-master1There we see the 5 static pods, with -cluster1-master1 as suffix.
We also see that the dns application seems to be coredns, but how is it controlled?
➜ root@cluster1-master1$ 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-master1$ kubectl -n kube-system get deploy
NAME READY UP-TO-DATE AVAILABLE AGE
coredns 2/2 2 2 155mSeems like coredns is controlled via a Deployment. We combine our findings in the requested file:
# /opt/course/8/master-components.txt
kubelet: process
kube-apiserver: static-pod
kube-scheduler: static-pod
kube-scheduler-special: static-pod (status CrashLoopBackOff)
kube-controller-manager: static-pod
etcd: static-pod
dns: pod corednsYou 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-AC
Ssh into the master node with ssh cluster2-master1. 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 its created but not scheduled on any node.
Now you're the scheduler and have all its power, manually schedule that Pod on node cluster2-master1. Make sure it's running.
Start the kube-scheduler again and confirm its running correctly by creating a second Pod named manual-schedule2 of image httpd:2.4-alpine and check if it's running on cluster2-worker1.
Answer: Stop the Scheduler First we find the master node:
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster2-master1 Ready master 26h v1.22.1
cluster2-worker1 Ready <none> 26h v1.22.1Then we connect and check if the scheduler is running:
➜ ssh cluster2-master1
➜ root@cluster2-master1:~# kubectl -n kube-system get pod | grep schedule
kube-scheduler-cluster2-master1 1/1 Running 0 6s
# Kill the Scheduler (temporarily):
➜ root@cluster2-master1:~# cd /etc/kubernetes/manifests/
➜ root@cluster2-master1:~# mv kube-scheduler.yaml ..
And it should be stopped:
➜ root@cluster2-master1:~# kubectl -n kube-system get pod | grep schedule
➜ root@cluster2-master1:~#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 wide
NAME 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-schedule
managedFields:
...
manager: kubectl-run
operation: Update
time: "2020-09-04T15:51:02Z"
name: manual-schedule
namespace: default
resourceVersion: "3515"
selfLink: /api/v1/namespaces/default/pods/manual-schedule
uid: 8e9d2532-4779-4e63-b5af-feb82c74a935
spec:
nodeName: cluster2-master1 # add the master node name
containers:
- image: httpd:2.4-alpine
imagePullPolicy: IfNotPresent
name: manual-schedule
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: default-token-nxnc7
readOnly: true
dnsPolicy: 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-master1It looks like our Pod is running on the master now as requested, although no tolerations were specified.
Only the scheduler takes trains/tolerations/affinity into account when finding the correct node name.
That's why its still possible to assign Pods manually directly to a master node and skip the scheduler.
Start the scheduler again
➜ ssh cluster2-master1
➜ root@cluster2-master1:~# cd /etc/kubernetes/manifests/
➜ root@cluster2-master1:~# mv ../kube-scheduler.yaml .
# Checks its running:
➜ root@cluster2-master1:~# kubectl -n kube-system get pod | grep schedule
kube-scheduler-cluster2-master1 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-master1
manual-schedule2 1/1 Running ... cluster2-worker1Back to normal.
Question 10 | RBAC ServiceAccount Role RoleBinding
Task 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:
TL;DR
k create ns project-hamster k create serviceaccount processor -n project-hamster k create role processor --verb=create --resource=secrets,configmaps -n project-hamster k create rolebinding processor --role=processor --serviceaccount=project-hamster:processor
Let's talk a little about RBAC resources A 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 solution We first create the ServiceAccount:
➜ k -n project-hamster create sa processor
serviceaccount/processor createdThen for the Role:
k -n project-hamster create role -h # examplesSo we execute:
k -n project-hamster create role processor \
--verb=create \
--resource=secret \
--resource=configmapWhich will create a Role like:
# kubectl -n project-hamster create role accessor --verb=create --resource=secret --resource=configmap
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
name: processor
namespace: project-hamster
rules:
- apiGroups:
- ""
resources:
- secrets
- configmaps
verbs:
- createNow we bind the Role to the ServiceAccount:
k -n project-hamster create rolebinding -h # examplesSo we create it:
k -n project-hamster create rolebinding processor \
--role processor \
--serviceaccount project-hamster:processorThis 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: processor
namespace: project-hamster
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: processor
subjects:
- kind: ServiceAccount
name: processor
namespace: project-hamsterTo test our RBAC setup we can use kubectl auth can-i:
k auth can-i -h # examplesLike 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
noDone.
Question 11 | DaemonSet on all Nodes
Task weight: 4%
Use context: kubectl config use-context k8s-c1-H
Use 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, master and worker.
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
vim 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: null
labels: # add
id: ds-important # add
uuid: 18426a0b-5f59-4e10-923f-c0e078e82462 # add
name: ds-important
namespace: project-tiger # important
spec:
#replicas: 1 # remove
selector:
matchLabels:
id: ds-important # add
uuid: 18426a0b-5f59-4e10-923f-c0e078e82462 # add
#strategy: {} # remove
template:
metadata:
creationTimestamp: null
labels:
id: ds-important # add
uuid: 18426a0b-5f59-4e10-923f-c0e078e82462 # add
spec:
containers:
- image: httpd:2.4-alpine
name: ds-important
resources:
requests: # add
cpu: 10m # add
memory: 10Mi # add
tolerations: # add
- effect: NoSchedule # add
key: node-role.kubernetes.io/master # add
#status: {} # removeIt 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-worker1
ds-important-lh5ts 1/1 Running ... cluster1-master1
ds-important-qhjcq 1/1 Running ... cluster1-worker2Question 12 | Deployment on all Nodes
Task weight: 6%
Use context: kubectl config use-context k8s-c1-H
Use 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-worker1 and cluster1-worker2. 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: 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
vim 12.yamlThen change the yaml to:
apiVersion: apps/v1
kind: Deployment
metadata:
creationTimestamp: null
labels:
id: very-important # change
name: deploy-important
namespace: project-tiger # important
spec:
replicas: 3 # change
selector:
matchLabels:
id: very-important # change
strategy: {}
template:
metadata:
creationTimestamp: null
labels:
id: very-important # change
spec:
containers:
- image: nginx:1.17.6-alpine
name: container1 # change
resources: {}
- image: kubernetes/pause # add
name: container2 # add
affinity: # add
podAntiAffinity: # add
requiredDuringSchedulingIgnoredDuringExecution: # add
- labelSelector: # add
matchExpressions: # add
- key: id # add
operator: In # add
values: # add
- very-important # add
topologyKey: kubernetes.io/hostname # add
status: {}Specify a topologyKey, which is a pre-populated Kubernetes label, you can find this by describing a node.
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-worker1
deploy-important-58db9db6fc-lnxdb 0/2 Pending ... <none>
deploy-important-58db9db6fc-p2rz8 2/2 Running ... cluster1-worker2If we kubectl describe the Pod deploy-important-58db9db6fc-lnxdb it will show us the reason for not scheduling is our implemented pod affinity/anti-affinity ruling:
Warning FailedScheduling 63s (x3 over 65s) default-scheduler 0/3 nodes are available: 1 node(s) had taint {node-role.kubernetes.io/master: }, 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.
Question 13 | Multi Containers and Pod shared Volume
Task weight: 4%
Use context: kubectl config use-context k8s-c1-H
Create 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
vim 13.yamlAnd add the other containers and the commands they should execute:
# 13.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: multi-container-playground
name: multi-container-playground
spec:
containers:
- image: nginx:1.17.6-alpine
name: c1 # change
resources: {}
env: # add
- name: MY_NODE_NAME # add
valueFrom: # add
fieldRef: # add
fieldPath: spec.nodeName # add
volumeMounts: # add
- name: vol # add
mountPath: /vol # add
- image: busybox:1.31.1 # add
name: c2 # add
command: ["sh", "-c", "while true; do date >> /vol/date.log; sleep 1; done"] # add
volumeMounts: # add
- name: vol # add
mountPath: /vol # add
- image: busybox:1.31.1 # add
name: c3 # add
command: ["sh", "-c", "tail -f /vol/date.log"] # add
volumeMounts: # add
- name: vol # add
mountPath: /vol # add
dnsPolicy: ClusterFirst
restartPolicy: Always
volumes: # add
- name: vol # add
emptyDir: {} # 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-playground
NAME READY STATUS RESTARTS AGE
multi-container-playground 3/3 Running 0 95sGood, 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-worker2And 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 2077Question 14 | Find out Cluster Information
Task weight: 2%
Use context: kubectl config use-context k8s-c1-H
You're ask to find out following information about the cluster k8s-c1-H:
How many master 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-worker1? Write your answers into file /opt/course/14/cluster-info, structured like this:
# /opt/course/14/cluster-info
1: [ANSWER]
2: [ANSWER]
3: [ANSWER]
4: [ANSWER]
5: [ANSWER]Answer: How many master and worker nodes are available?
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster1-master1 Ready master 27h v1.22.1
cluster1-worker1 Ready <none> 27h v1.22.1
cluster1-worker2 Ready <none> 27h v1.22.1We see one master and two workers.
What is the Service CIDR?
➜ ssh cluster1-master1
➜ root@cluster1-master1:~# cat /etc/kubernetes/manifests/kube-apiserver.yaml | grep range
- --service-cluster-ip-range=10.96.0.0/12Which Networking (or CNI Plugin) is configured and where is its config file?
➜ root@cluster1-master1:~# find /etc/cni/net.d/
/etc/cni/net.d/
/etc/cni/net.d/10-weave.conflist
➜ root@cluster1-master1:~# 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 master and worker nodes.
Which suffix will static pods have that run on cluster1-worker1? 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 master 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-worker1?
5: -cluster1-worker1Question 15 | Cluster Event Logging
Task weight: 3%
Use context: kubectl config use-context k8s-c2-AC
Write a command into /opt/course/15/cluster_events.sh which shows the latest events in the whole cluster, ordered by time. Use kubectl for it.
Now kill the kube-proxy Pod running on node cluster2-worker1 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-worker1 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.creationTimestampNow we kill the kube-proxy Pod:
k -n kube-system get pod -o wide | grep proxy # find pod running on cluster2-worker1
k -n kube-system delete pod kube-proxy-z64cgNow 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-worker1 ...
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-worker1
➜ root@cluster2-worker1:~# crictl ps | grep kube-proxy
1e020b43c4423 36c4ebbc9d979 About an hour ago Running kube-proxy ...
➜ root@cluster2-worker1:~# crictl rm 1e020b43c4423
1e020b43c4423
➜ root@cluster2-worker1:~# 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-H
Create a new Namespace called cka-master.
Write 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 We create a new Namespace:
k create ns cka-master 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.txtWhich 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.ioNamespace 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.
0Finally we write the name and amount into the file:
# /opt/course/16/crowded-namespace.txt
project-c14 with 300 resourcesQuestion 17 | Find Container of Pod and check info
Task weight: 3%
Use context: kubectl config use-context k8s-c1-H
In 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.txt Write 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-worker2
➜ root@cluster1-worker2:~# crictl ps | grep tigers-reunite
b01edbe6f89ed 54b0995a63052 5 seconds ago Running tigers-reunite ...
➜ root@cluster1-worker2:~# 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.v2Finally we write the container logs in the second file:
ssh cluster1-worker2 '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 its 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-CCC
There seems to be an issue with the kubelet not running on cluster3-worker1. Fix it and confirm that cluster has node cluster3-worker1 available in Ready state afterwards. You should be able to schedule a Pod on cluster3-worker1 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 node
NAME STATUS ROLES AGE VERSION
cluster3-master1 Ready master 27h v1.22.1
cluster3-worker1 NotReady <none> 26h v1.22.1First we check if the kubelet is running:
➜ ssh cluster3-worker1
➜ root@cluster3-worker1:~# ps aux | grep kubelet
root 29294 0.0 0.2 14856 1016 pts/0 S+ 11:30 0:00 grep --color=auto kubeletNope, so we check if its configured using systemd as service:
➜ root@cluster3-worker1:~# service kubelet status
● kubelet.service - kubelet: The Kubernetes Node Agent
Loaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/kubelet.service.d
└─10-kubeadm.conf
Active: inactive (dead) since Sun 2019-12-08 11:30:06 UTC; 50min 52s ago
...Yes, its configured as a service with config at /etc/systemd/system/kubelet.service.d/10-kubeadm.conf, but we see its inactive. Let's try to start it:
➜ root@cluster3-worker1:~# service kubelet start
➜ root@cluster3-worker1:~# service kubelet status
● kubelet.service - kubelet: The Kubernetes Node Agent
Loaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/kubelet.service.d
└─10-kubeadm.conf
Active: activating (auto-restart) (Result: exit-code) since Thu 2020-04-30 22:03:10 UTC; 3s ago
Docs: 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-worker1 systemd[5989]: kubelet.service: Failed at step EXEC spawning /usr/local/bin/kubelet: No such file or directory
Apr 30 22:03:10 cluster3-worker1 systemd[1]: kubelet.service: Main process exited, code=exited, status=203/EXEC
Apr 30 22:03:10 cluster3-worker1 systemd[1]: kubelet.service: Failed with result 'exit-code'.We see its 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-worker1:~# /usr/local/bin/kubelet
-bash: /usr/local/bin/kubelet: No such file or directory➜ root@cluster3-worker1:~# 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 runningAlso 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-master1 Ready master 27h v1.22.1
cluster3-worker1 Ready <none> 27h v1.22.1Finally we write the reason into the file:
# /opt/course/18/reason.txt
wrong path to kubelet binary specified in service configQuestion 19 | Create Secret and mount into Pod
Task weight: 3%
Use context: kubectl config use-context k8s-c3-CCC
Do 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. It should be able to run on master nodes as well, create the proper toleration.
There is an existing Secret located at /opt/course/19/secret1.yaml, create it in the secret Namespace 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
vim 19_secret1.yamlWe need to adjust the Namespace for that Secret:
# 19_secret1.yaml
apiVersion: v1
data:
halt: IyEgL2Jpbi9zaAo...
kind: Secret
metadata:
creationTimestamp: null
name: secret1
namespace: secret # changek -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
vim 19.yaml Then make the necessary changes:
# 19.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: secret-pod
name: secret-pod
namespace: secret # add
spec:
tolerations: # add
- effect: NoSchedule # add
key: node-role.kubernetes.io/master # add
containers:
- args:
- sh
- -c
- sleep 1d
image: busybox:1.31.1
name: secret-pod
resources: {}
env: # add
- name: APP_USER # add
valueFrom: # add
secretKeyRef: # add
name: secret2 # add
key: user # add
- name: APP_PASS # add
valueFrom: # add
secretKeyRef: # add
name: secret2 # add
key: pass # add
volumeMounts: # add
- name: secret1 # add
mountPath: /tmp/secret1 # add
readOnly: true # add
dnsPolicy: ClusterFirst
restartPolicy: Always
volumes: # add
- name: secret1 # add
secret: # add
secretName: 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-CCC
Your coworker said node cluster3-worker2 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-master1. Then add this node to the cluster. Use kubeadm for this.
Answer: Upgrade Kubernetes to cluster3-master1 version Search in the docs for kubeadm upgrade: https://kubernetes.io/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster3-master1 Ready control-plane,master 116m v1.22.1
cluster3-worker1 NotReady <none> 112m v1.22.1Master node seems to be running Kubernetes 1.22.1 and cluster3-worker2 is not yet part of the cluster.
➜ ssh cluster3-worker2
➜ root@cluster3-worker2:~# kubeadm version
ubeadm version: &version.Info{Major:"1", Minor:"22", GitVersion:"v1.22.1", GitCommit:"632ed300f2c34f6d6d15ca4cef3d3c7073412212", GitTreeState:"clean", BuildDate:"2021-08-19T15:44:22Z", GoVersion:"go1.16.7", Compiler:"gc", Platform:"linux/amd64"}
➜ root@cluster3-worker2:~# kubectl version
Client Version: version.Info{Major:"1", Minor:"21", GitVersion:"v1.21.4", GitCommit:"3cce4a82b44f032d0cd1a1790e6d2f5a55d20aae", GitTreeState:"clean", BuildDate:"2021-08-11T18:16:05Z", GoVersion:"go1.16.7", Compiler:"gc", Platform:"linux/amd64"}
The connection to the server localhost:8080 was refused - did you specify the right host or port?
➜ root@cluster3-worker2:~# kubelet --version
Kubernetes v1.21.4Here kubeadm is already installed in the wanted version, so we can run:
➜ root@cluster3-worker2:~# 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 directory
To see the stack trace of this error execute with --v=5 or higher
This 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-worker2:~# apt-get update
...
➜ root@cluster3-worker2:~# apt-cache show kubectl | grep 1.22
Version: 1.22.1-00
Filename: pool/kubectl_1.22.1-00_amd64_2a00cd912bfa610fe4932bc0a557b2dd7b95b2c8bff9d001dc6b3d34323edf7d.deb
Version: 1.22.0-00
Filename: pool/kubectl_1.22.0-00_amd64_052395d9ddf0364665cf7533aa66f96b310ec8a2b796d21c42f386684ad1fc56.deb
Filename: pool/kubectl_1.17.1-00_amd64_0dc19318c9114db2931552bb8bf650a14227a9603cb73fe0917ac7868ec7fcf0.deb
SHA256: 0dc19318c9114db2931552bb8bf650a14227a9603cb73fe0917ac7868ec7fcf0
...
➜ root@cluster3-worker2:~# apt-get install kubectl=1.22.1-00 kubelet=1.22.1-00
Reading package lists... Done
Building dependency tree
Reading state information... Done
...
Preparing to unpack .../kubectl_1.22.1-00_amd64.deb ...
Unpacking kubectl (1.22.1-00) over (1.21.4-00) ...
Preparing to unpack .../kubelet_1.22.1-00_amd64.deb ...
Unpacking kubelet (1.22.1-00) over (1.21.4-00) ...
Setting up kubectl (1.22.1-00) ...
Setting up kubelet (1.22.1-00) ...
➜ root@cluster3-worker2:~# kubelet --version
Kubernetes v1.22.1
Now we're up to date with kubeadm, kubectl and kubelet. Restart the kubelet:
➜ root@cluster3-worker2:~# systemctl restart kubelet
➜ root@cluster3-worker2:~# service kubelet status
...$KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS (code=exited, status=255)
Main PID: 21457 (code=exited, status=255)
...
Apr 30 22:15:08 cluster3-worker2 systemd[1]: kubelet.service: Main process exited, code=exited, status=255/n/a
Apr 30 22:15:08 cluster3-worker2 systemd[1]: kubelet.service: Failed with result 'exit-code'.
We can ignore the errors and move into next step to generate the join command.Add cluster3-master2 to cluster First we log into the master1 and generate a new TLS bootstrap token, also printing out the join command:
➜ ssh cluster3-master1
➜ root@cluster3-master1:~# kubeadm token create --print-join-command
kubeadm join 192.168.100.31:6443 --token leqq1l.1hlg4rw8mu7brv73 --discovery-token-ca-cert-hash sha256:2e2c3407a256fc768f0d8e70974a8e24d7b9976149a79bd08858c4d7aa2ff79a
➜ root@cluster3-master1:~# kubeadm token list
TOKEN TTL EXPIRES ...
mnkpfu.d2lpu8zypbyumr3i 23h 2020-05-01T22:43:45Z ...
poa13f.hnrs6i6ifetwii75 <forever> <never> ...
We see the expiration of 23h for our token, we could adjust this by passing the ttl argument.Next we connect again to worker2 and simply execute the join command:
➜ ssh cluster3-worker2
➜ root@cluster3-worker2:~# kubeadm join 192.168.100.31:6443 --token leqq1l.1hlg4rw8mu7brv73 --discovery-token-ca-cert-hash sha256:2e2c3407a256fc768f0d8e70974a8e24d7b9976149a79bd08858c4d7aa2ff79a
[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-worker2:~# service kubelet status
● kubelet.service - kubelet: The Kubernetes Node Agent
Loaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/kubelet.service.d
└─10-kubeadm.conf
Active: active (running) since Wed 2021-09-15 17:12:32 UTC; 42s ago
Docs: https://kubernetes.io/docs/home/
Main PID: 24771 (kubelet)
Tasks: 13 (limit: 467)
Memory: 68.0M
CGroup: /system.slice/kubelet.service
└─24771 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kuber>
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 node
NAME STATUS ROLES AGE VERSION
cluster3-master1 Ready control-plane,master 24h v1.22.1
cluster3-worker1 Ready <none> 24h v1.22.1
cluster3-worker2 NotReady <none> 32s v1.22.1Give it a bit of time till the node is ready.
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster3-master1 Ready control-plane,master 24h v1.22.1
cluster3-worker1 Ready <none> 24h v1.22.1
cluster3-worker2 Ready <none> 107s v1.22.1We see cluster3-worker2 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-CCC
Create a Static Pod named my-static-pod in Namespace default on cluster3-master1. 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 its reachable through the cluster3-master1 internal IP address. You can connect to the internal node IPs from your main terminal.
Answer:
➜ ssh cluster3-master1
➜ root@cluster1-master1:~# cd /etc/kubernetes/manifests/
➜ root@cluster1-master1:~# kubectl run my-static-pod \
--image=nginx:1.16-alpine \
-o yaml --dry-run=client > my-static-pod.yamlThen 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: null
labels:
run: my-static-pod
name: my-static-pod
spec:
containers:
- image: nginx:1.16-alpine
name: my-static-pod
resources:
requests:
cpu: 10m
memory: 20Mi
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}And make sure its running:
➜ k get pod -A | grep my-static
NAMESPACE NAME READY STATUS ... AGE
default my-static-pod-cluster3-master1 1/1 Running ... 22sNow we expose that static Pod:
k expose pod my-static-pod-cluster3-master1 \
--name static-pod-service \
--type=NodePort \
--port 80This would generate a Service like:
# kubectl expose pod my-static-pod-cluster3-master1 --name static-pod-service --type=NodePort --port 80
apiVersion: v1
kind: Service
metadata:
creationTimestamp: null
labels:
run: my-static-pod
name: static-pod-service
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
run: my-static-pod
type: 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 30sLooking good.
Question 22 | Check how long certificates are valid
Task weight: 2%
Use context: kubectl config use-context k8s-c2-AC
Check how long the kube-apiserver server certificate is valid on cluster2-master1. 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-master1
➜ root@cluster2-master1:~# 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.keyNext we use openssl to find out the expiration date:
➜ root@cluster2-master1:~# openssl x509 -noout -text -in /etc/kubernetes/pki/apiserver.crt | grep Validity -A2
Validity
Not Before: Jan 14 18:18:15 2021 GMT
Not After : Jan 14 18:49:40 2022 GMTThere we have it, so we write it in the required location on our main terminal:
# /opt/course/22/expiration
Jan 14 18:49:40 2022 GMTAnd we use the feature from kubeadm to get the expiration too:
➜ root@cluster2-master1:~# kubeadm certs check-expiration | grep apiserver
apiserver 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 noLooking 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 apiserverQuestion 23 | Kubelet client/server cert info
Task weight: 2%
Use context: kubectl config use-context k8s-c2-AC
Node cluster2-worker1 has been added to the cluster using kubeadm and TLS bootstrapping.
Find the "Issuer" and "Extended Key Usage" values of the cluster2-worker1:
- 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-worker1
➜ root@cluster2-worker1:~# openssl x509 -noout -text -in /var/lib/kubelet/pki/kubelet-client-current.pem | grep Issuer
Issuer: CN = kubernetes
➜ root@cluster2-worker1:~# openssl x509 -noout -text -in /var/lib/kubelet/pki/kubelet-client-current.pem | grep "Extended Key Usage" -A1
X509v3 Extended Key Usage:
TLS Web Client AuthenticationNext we check the kubelet server certificate:
➜ root@cluster2-worker1:~# openssl x509 -noout -text -in /var/lib/kubelet/pki/kubelet.crt | grep Issuer
Issuer: CN = cluster2-worker1-ca@1588186506
➜ root@cluster2-worker1:~# openssl x509 -noout -text -in /var/lib/kubelet/pki/kubelet.crt | grep "Extended Key Usage" -A1
X509v3 Extended Key Usage:
TLS Web Server AuthenticationWe 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 its 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-H
There 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 1111
- connect to db2-* Pods on port 2222 Use 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 vaultWe 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 storageNow we create the NP by copying and chaning an example from the k8s docs:
vim 24_np.yaml
# 24_np.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: np-backend
namespace: project-snake
spec:
podSelector:
matchLabels:
app: backend
policyTypes:
- Egress # policy is only about Egress
egress:
- # first rule
to: # first condition "to"
- podSelector:
matchLabels:
app: db1
ports: # second condition "port"
- protocol: TCP
port: 1111
- # second rule
to: # first condition "to"
- podSelector:
matchLabels:
app: db2
ports: # second condition "port"
- protocol: TCP
port: 2222The 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-backend
namespace: project-snake
spec:
podSelector:
matchLabels:
app: backend
policyTypes:
- Egress
egress:
- # first rule
to: # first condition "to"
- podSelector: # first "to" possibility
matchLabels:
app: db1
- podSelector: # second "to" possibility
matchLabels:
app: db2
ports: # second condition "ports"
- protocol: TCP # first "ports" possibility
port: 1111
- protocol: TCP # second "ports" possibility
port: 2222The 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
^CAlso 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-CCC
Make a backup of etcd running on cluster3-master1 and save it on the master 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 master and try to create a snapshop of etcd:
➜ ssh cluster3-master1
➜ root@cluster3-master1:~# ETCDCTL_API=3 etcdctl snapshot save /tmp/etcd-backup.db
Error: rpc error: code = Unavailable desc = transport is closingBut it fails because we need to authenticate ourselves. For the necessary information we can check the etc manifest:
➜ root@cluster3-master1:~# vim /etc/kubernetes/manifests/etcd.yamlWe only check the etcd.yaml for necessary information we don't change it.
# /etc/kubernetes/manifests/etcd.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
component: etcd
tier: control-plane
name: etcd
namespace: 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-master1=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-master1
- --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.crt
image: k8s.gcr.io/etcd:3.3.15-0
imagePullPolicy: IfNotPresent
livenessProbe:
failureThreshold: 8
httpGet:
host: 127.0.0.1
path: /health
port: 2381
scheme: HTTP
initialDelaySeconds: 15
timeoutSeconds: 15
name: etcd
resources: {}
volumeMounts:
- mountPath: /var/lib/etcd
name: etcd-data
- mountPath: /etc/kubernetes/pki/etcd
name: etcd-certs
hostNetwork: true
priorityClassName: system-cluster-critical
volumes:
- hostPath:
path: /etc/kubernetes/pki/etcd
type: DirectoryOrCreate
name: etcd-certs
- hostPath:
path: /var/lib/etcd # important
type: DirectoryOrCreate
name: 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-master1:~# 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://127.0.0.1:2379We use the authentication information and pass it to etcdctl:
➜ root@cluster3-master1:~# 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.keySnapshot 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-master1:~# kubectl run test --image=nginx
pod/test created
➜ root@cluster3-master1:~# kubectl get pod -l run=test -w
NAME READY STATUS RESTARTS AGE
test 1/1 Running 0 60sNOTE: 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-master1:~# cd /etc/kubernetes/manifests/
root@cluster3-master1:/etc/kubernetes/manifests# mv * ..
root@cluster3-master1:/etc/kubernetes/manifests# watch crictl psNow we restore the snapshot into a specific directory:
➜ root@cluster3-master1:~# 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 cdf818194e3a8c32We 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-master1:~# vim /etc/kubernetes/etcd.yaml
# /etc/kubernetes/etcd.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
component: etcd
tier: control-plane
name: etcd
namespace: kube-system
spec:
...
- mountPath: /etc/kubernetes/pki/etcd
name: etcd-certs
hostNetwork: true
priorityClassName: system-cluster-critical
volumes:
- hostPath:
path: /etc/kubernetes/pki/etcd
type: DirectoryOrCreate
name: etcd-certs
- hostPath:
path: /var/lib/etcd-backup # change
type: DirectoryOrCreate
name: 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-master1:/etc/kubernetes/manifests# mv ../*.yaml .
root@cluster3-master1:/etc/kubernetes/manifests# watch crictl psThen we check again for the Pod:
➜ root@cluster3-master1:~# 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-H
Check 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 scenarioTo 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 BestEffortHere 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-H
There 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 $do \
--command > e2.yaml -- sh -c 'sleep 1d'
vim e2.yamlAdd the service account name and Namespace:
# e2.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: tmp-api-contact
name: tmp-api-contact
namespace: project-hamster # add
spec:
serviceAccountName: secret-reader # add
containers:
- command:
- sh
- -c
- sleep 1d
image: curlimages/curl:7.65.3
name: tmp-api-contact
resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}Then run and exec into:
k -f 6.yaml create
k -n project-hamster exec tmp-api-contact -it -- shOnce on the container we can try to connect to the api using curl, the api is usually available via the Service named kubernetes in Namespace default (You should know how dns resolution works across Namespaces.). Else we can find the endpoint IP via environment variables running env.
So now we can do:
curl https://kubernetes.default
curl -k https://kubernetes.default # ignore insecure as allowed in ticket description
curl -k https://kubernetes.default/api/v1/secrets # should show Forbidden 403The last command shows 403 forbidden, this is because we are not passing any authorisation information with us. The Kubernetes Api Server thinks we are connecting as system:anonymous. We want to change this and connect using the Pods ServiceAccount named secret-reader.
We find the the token in the mounted folder at /var/run/secrets/kubernetes.io/serviceaccount, so we do:
➜ TOKEN=$(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 Current
Dload Upload Total Spent Left Speed
0 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 ${TOKEN}"For troubleshooting we could also check if the ServiceAccount is actually able to list Secrets using:
➜ k auth can-i get secret --as system:serviceaccount:project-hamster:secret-reader
yesFinally write the commands into the requested location:
# /opt/course/e4/list-secrets.sh
TOKEN=$(cat /var/run/secrets/kubernetes.io/serviceaccount/token)
curl -k https://kubernetes.default/api/v1/secrets -H "Authorization: Bearer ${TOKEN}"CKA Simulator Preview Kubernetes 1.22
This is a preview of the full CKA Simulator course content.
The full course contains 25 scenarios from all the CKA areas. The course also provides a browser terminal which is a very close replica of the original one. This is great to get used and comfortable before the real exam. After the test session (120 minutes), or if you stop it early, you'll get access to all questions and their detailed solutions. You'll have 36 hours cluster access in total which means even after the session, once you have the solutions, you can still play around.
The following preview will give you an idea of what the full course will provide. These preview questions are in addition to the 25 of the full course. But the preview questions are part of the same CKA simulation environment which we setup for you, so with access to the full course you can solve these too.
The answers provided here assume that you did run the initial terminal setup suggestions as provided in the tips section, but especially:
alias k=kubectl
export do="-o yaml --dry-run=client"These questions can be solved in the test environment provided through the CKA Simulator
Preview Question 1
Use context: kubectl config use-context k8s-c2-AC
The cluster admin asked you to find out the following information about etcd running on cluster2-master1:
- Server private key location
- Server certificate expiration date
- Is client certificate authentication enabled Write 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-master1 and display its status.
Answer: Find out etcd information Let's check the nodes:
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster2-master1 Ready master 89m v1.22.1
cluster2-worker1 Ready <none> 87m v1.22.1
➜ ssh cluster2-master1First we check how etcd is setup in this cluster:
➜ root@cluster2-master1:~# 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-master1 1/1 Running 0 26h
kube-apiserver-cluster2-master1 1/1 Running 0 26h
kube-controller-manager-cluster2-master1 1/1 Running 0 26h
kube-proxy-qthfg 1/1 Running 0 25h
kube-proxy-z55lp 1/1 Running 0 26h
kube-scheduler-cluster2-master1 1/1 Running 1 26h
weave-net-cqdvt 2/2 Running 0 26h
weave-net-dxzgh 2/2 Running 1 25hWe see its running as a Pod, more specific a static Pod. So we check for the default kubelet directory for static manifests:
➜ root@cluster2-master1:~# 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-master1:~# vim /etc/kubernetes/manifests/etcd.yamlSo we look at the yaml and the parameters with which etcd is started:
# /etc/kubernetes/manifests/etcd.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
component: etcd
tier: control-plane
name: etcd
namespace: 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-master1=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-master1
- --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-master1:~# openssl x509 -noout -text -in /etc/kubernetes/pki/etcd/server.crt | grep Validity -A2
Validity
Not Before: Sep 13 13:01:31 2021 GMT
Not After : Sep 13 13:01:31 2022 GMTThere we have it. Let's write the information into the requested file:
# /opt/course/p1/etcd-info.txt
Server 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: yesCreate 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.keyThis worked. Now we can output the status of the backup file:
➜ root@cluster2-master1:~# ETCDCTL_API=3 etcdctl snapshot status /etc/etcd-snapshot.db
4d4e953, 7213, 1291, 2.7 MBThe status shows:
- Hash: 4d4e953
- Revision: 7213
- Total Keys: 1291
- Total Size: 2.7 MB
Preview Question 2
Use context: kubectl config use-context k8s-c1-H
You'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-master1, cluster1-worker1 and cluster1-worker2 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 $do
k run p2-pod --image=nginx:1.21.3-alpine $do > p2.yaml
vim p2.yamlNext we add the requested second container:
# p2.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: p2-pod
name: p2-pod
namespace: project-hamster # add
spec:
containers:
- image: nginx:1.21.3-alpine
name: p2-pod
- image: busybox:1.31 # add
name: c2 # add
command: ["sh", "-c", "sleep 1d"] # add
resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}And we create the Pod:
k -f p2.yaml create
Create the Service Next we create the Service:
k -n project-hamster expose pod p2-pod --name p2-service --port 3000 --target-port 80 This will create a yaml like:
apiVersion: v1
kind: Service
metadata:
creationTimestamp: "2020-04-30T20:58:14Z"
labels:
run: p2-pod
managedFields:
...
operation: Update
time: "2020-04-30T20:58:14Z"
name: p2-service
namespace: project-hamster
resourceVersion: "11071"
selfLink: /api/v1/namespaces/project-hamster/services/p2-service
uid: 2a1c0842-7fb6-4e94-8cdb-1602a3b1e7d2
spec:
clusterIP: 10.97.45.18
ports:
- port: 3000
protocol: TCP
targetPort: 80
selector:
run: p2-pod
sessionAffinity: None
type: ClusterIP
status:
loadBalancer: {}We should confirm Pods and Services are connected, hence the Service should have Endpoints.
k -n project-hamster get pod,svc,ep
Confirm kube-proxy is running and is using iptables First we get nodes in the cluster:
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster1-master1 Ready master 98m v1.22.1
cluster1-worker1 Ready <none> 96m v1.22.1
cluster1-worker2 Ready <none> 95m v1.22.1The idea here is to log into every node, find the kube-proxy container and check its logs:
➜ ssh cluster1-master1
➜ root@cluster1-master1$ crictl ps | grep kube-proxy
27b6a18c0f89c 36c4ebbc9d979 3 hours ago Running kube-proxy
➜ root@cluster1-master1~# 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-master1 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-worker1 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-worker2 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-6U447UXLLQIKP7BBGreat. Now let's write these logs into the requested file:
➜ ssh cluster1-master1 iptables-save | grep p2-service >> /opt/course/p2/iptables.txt
➜ ssh cluster1-worker1 iptables-save | grep p2-service >> /opt/course/p2/iptables.txt
➜ ssh cluster1-worker2 iptables-save | grep p2-service >> /opt/course/p2/iptables.txtDelete 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-master1 iptables-save | grep p2-service
➜ ssh cluster1-worker1 iptables-save | grep p2-service
➜ ssh cluster1-worker2 iptables-save | grep p2-serviceDone.
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-AC
Create 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 80And 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 7sNow we change the Service CIDR on the kube-apiserver:
➜ ssh cluster2-master1
➜ root@cluster2-master1:~# vim /etc/kubernetes/manifests/kube-apiserver.yaml# /etc/kubernetes/manifests/kube-apiserver.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
component: kube-apiserver
tier: control-plane
name: kube-apiserver
namespace: 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-master1:~# kubectl -n kube-system get pod | grep api
kube-apiserver-cluster2-master1 1/1 Running 0 49sNow we do the same for the controller manager:
➜ root@cluster2-master1:~# vim /etc/kubernetes/manifests/kube-controller-manager.yaml
# /etc/kubernetes/manifests/kube-controller-manager.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
component: kube-controller-manager
tier: control-plane
name: kube-controller-manager
namespace: 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=trueGive it a bit for the controller-manager to restart.
We can check if it was restarted using crictl:
➜ root@cluster2-master1:~# 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 21m
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/check-ip-service ClusterIP 10.99.32.177 <none> 80/TCP 21mNothing 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 6m32s
NAME ENDPOINTS AGE
endpoints/check-ip-service 10.44.0.1:80 8m
endpoints/check-ip-service2 10.44.0.1:80 6m13sThere 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 1.22
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.
Resources
The majority of tasks in the CKA will also be around creating Kubernetes resources, like its tested in the CKAD. So we suggest to do:
- Maybe 2–3 times https://github.com/dgkanatsios/CKAD-exercises
- The CKAD series with scenarios on Medium
- The CKA series with scenarios on Medium
- Imagine and create your own scenarios to solve
- Know advanced scheduling: https://kubernetes.io/docs/concepts/scheduling/kube-scheduler
Components
- The other part is understanding Kubernetes components and being able to fix and investigate clusters. Understand this: https://kubernetes.io/docs/tasks/debug-application-cluster/debug-cluster
- When you have to fix a component (like kubelet) in one cluster, just check how its 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 master, 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
General
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
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. You can have one browser tab open with one of the allowed links: https://kubernetes.io/docs https://github.com/kubernetes https://kubernetes.io/blog
NOTE: You can have the other tab open as a separate window, this is why a big screen is handy
Deprecated commands
Make sure to not depend on deprecated commands as they might stop working at any time. When you execute a deprecated kubectl command a message will be shown, so you know which ones to avoid.
With kubectl version 1.18+ things have changed. Like its no longer possible to use kubectl run to create Jobs, CronJobs or Deployments, only Pods still work. This makes things a bit more verbose when you for example need to create a Deployment with resource limits or multiple replicas.
What if we need to create a Deployment which has, for example, a resources section? We could use both kubectl run and kubectl create, then do some vim magic. Read more 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.
Your Desktop
You are allowed to have multiple monitors connected and have to share every monitor with the proctor. Having one large screen definitely helps as you’re only allowed one application open (Chrome Browser) with two tabs, one terminal and one k8s docs.
NOTE: You can have the other tab open as a separate window, this is why a big screen is handy
The questions will be on the left (default maybe ~30% space), the terminal on the right. You can adjust the size of the split though to your needs in the real exam.
If you use a laptop you could work with lid closed, external mouse+keyboard+monitor attached. Make sure you also have a webcam+microphone working.
You could also have both monitors, laptop screen and external, active. You might be asked that your webcam points straight into your face. So using an external screen and your laptop webcam could not be accepted. Just keep that in mind.
You have to be able to move your webcam around in the beginning to show your whole room and desktop. Have a clean desk with only the necessary on it. You can have a glass/cup with water without anything printed on.
In the end you should feel very comfortable with your setup.
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 be configured together with autocompletion. In case not you can configure it using this link.
Vim
Create the file ~/.vimrc with the following content:
set tabstop=2
set expandtab
set shiftwidth=2The 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.
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 configuredVim
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© 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 PIndent multiple lines
In case not defined in .vimrc, 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