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Configuration (18%)

ConfigMaps

SecurityContext

Requests and Limits

Secrets

Service Accounts


#Tips, export to variable

export ns="-n secret-ops"

export do="--dry-run=client -oyaml"

ConfigMaps

kubernetes.io > Documentation > Tasks > Configure Pods and Containers > Configure a Pod to Use a ConfigMap

Create a configmap named config with values foo=lala,foo2=lolo

show 

kubectl create configmap config --from-literal=foo=lala --from-literal=foo2=lolo

Display its values

show 

kubectl get cm config -o yaml
# or
kubectl describe cm config

Create and display a configmap from a file

Create the file with

echo -e "foo3=lili\nfoo4=lele" > config.txt
show 

kubectl create cm configmap2 --from-file=config.txt
kubectl get cm configmap2 -o yaml

Create and display a configmap from a .env file

Create the file with the command

echo -e "var1=val1\n# this is a comment\n\nvar2=val2\n#anothercomment" > config.env
show 

kubectl create cm configmap3 --from-env-file=config.env
kubectl get cm configmap3 -o yaml

Create and display a configmap from a file, giving the key 'special'

Create the file with

echo -e "var3=val3\nvar4=val4" > config4.txt
show 

kubectl create cm configmap4 --from-file=special=config4.txt
kubectl describe cm configmap4
kubectl get cm configmap4 -o yaml

Create a configMap called 'options' with the value var5=val5. Create a new nginx pod that loads the value from variable 'var5' in an env variable called 'option'

show 

kubectl create cm options --from-literal=var5=val5
kubectl run nginx --image=nginx --restart=Never --dry-run=client -o yaml > pod.yaml
vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    env:
    - name: option # name of the env variable
      valueFrom:
        configMapKeyRef:
          name: options # name of config map
          key: var5 # name of the entity in config map
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}
kubectl create -f pod.yaml
kubectl exec -it nginx -- env | grep option # will show 'option=val5'

Create a configMap 'anotherone' with values 'var6=val6', 'var7=val7'. Load this configMap as env variables into a new nginx pod

show 

kubectl create configmap anotherone --from-literal=var6=val6 --from-literal=var7=val7
kubectl run --restart=Never nginx --image=nginx -o yaml --dry-run=client > pod.yaml
vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    envFrom: # different than previous one, that was 'env'
    - configMapRef: # different from the previous one, was 'configMapKeyRef'
        name: anotherone # the name of the config map
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}
kubectl create -f pod.yaml
kubectl exec -it nginx -- env

Create a configMap 'cmvolume' with values 'var8=val8', 'var9=val9'. Load this as a volume inside an nginx pod on path '/etc/lala'. Create the pod and 'ls' into the '/etc/lala' directory.

show 

kubectl create configmap cmvolume --from-literal=var8=val8 --from-literal=var9=val9
kubectl run nginx --image=nginx --restart=Never -o yaml --dry-run=client > pod.yaml
vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  volumes: # add a volumes list
  - name: myvolume # just a name, you'll reference this in the pods
    configMap:
      name: cmvolume # name of your configmap
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    volumeMounts: # your volume mounts are listed here
    - name: myvolume # the name that you specified in pod.spec.volumes.name
      mountPath: /etc/lala # the path inside your container
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}
kubectl create -f pod.yaml
kubectl exec -it nginx -- /bin/sh
cd /etc/lala
ls # will show var8 var9
cat var8 # will show val8

SecurityContext

kubernetes.io > Documentation > Tasks > Configure Pods and Containers > Configure a Security Context for a Pod or Container

Create the YAML for an nginx pod that runs with the user ID 101. No need to create the pod

show 

kubectl run nginx --image=nginx --restart=Never --dry-run=client -o yaml > pod.yaml
vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  securityContext: # insert this line
    runAsUser: 101 # UID for the user
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

Create the YAML for an nginx pod that has the capabilities "NET_ADMIN", "SYS_TIME" added to its single container

show 

kubectl run nginx --image=nginx --restart=Never --dry-run=client -o yaml > pod.yaml
vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    securityContext: # insert this line
      capabilities: # and this
        add: ["NET_ADMIN", "SYS_TIME"] # this as well
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

Resource requests and limits

kubernetes.io > Documentation > Tasks > Configure Pods and Containers > Assign CPU Resources to Containers and Pods

Create an nginx pod with requests cpu=100m,memory=256Mi and limits cpu=200m,memory=512Mi

show 

kubectl run nginx --image=nginx --dry-run=client -o yaml > pod.yaml
vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    name: nginx
    resources:
      requests:
        memory: "256Mi"
        cpu: "100m"
      limits:    
        memory: "512Mi"
        cpu: "200m"
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

Limit Ranges

kubernetes.io > Documentation > Concepts > Policies > Limit Ranges (https://kubernetes.io/docs/concepts/policy/limit-range/)

Create a namespace named limitrange with a LimitRange that limits pod memory to a max of 500Mi and min of 100Mi

show 

kubectl create ns limitrange

vi 1.yaml

apiVersion: v1
kind: LimitRange
metadata:
  name: ns-memory-limit
  namespace: limitrange
spec:
  limits:
  - max: # max and min define the limit range
      memory: "500Mi"
    min:
      memory: "100Mi"
    type: Container
kubectl apply -f 1.yaml

Describe the namespace limitrange

show 

kubectl describe limitrange ns-memory-limit -n limitrange

Create an nginx pod that requests 250Mi of memory in the limitrange namespace

show

vi 2.yaml

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
  namespace: limitrange
spec:
  containers:
  - image: nginx
    name: nginx
    resources:
      requests:
        memory: "250Mi"
      limits:
        memory: "500Mi" # limit has to be specified and be <= limitrange
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}
kubectl apply -f 2.yaml

Resource Quotas

kubernetes.io > Documentation > Concepts > Policies > Resource Quotas (https://kubernetes.io/docs/concepts/policy/resource-quotas/)

Create ResourceQuota in namespace one with hard requests cpu=1, memory=1Gi and hard limits cpu=2, memory=2Gi.

show

Create the namespace:

kubectl create ns one

Create the ResourceQuota

vi rq-one.yaml
apiVersion: v1
kind: ResourceQuota
metadata:
  name: my-rq
  namespace: one
spec:
  hard:
    requests.cpu: "1"
    requests.memory: 1Gi
    limits.cpu: "2"
    limits.memory: 2Gi
kubectl apply -f rq-one.yaml

or

kubectl create quota my-rq --namespace=one --hard=requests.cpu=1,requests.memory=1Gi,limits.cpu=2,limits.memory=2Gi

Attempt to create a pod with resource requests cpu=2, memory=3Gi and limits cpu=3, memory=4Gi in namespace one

show 

vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
  namespace: one
spec:
  containers:
  - image: nginx
    name: nginx
    resources:
      requests:
        memory: "3Gi"
        cpu: "2"
      limits:
        memory: "4Gi"
        cpu: "3"
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}
kubectl create -f pod.yaml

Expected error message:

Error from server (Forbidden): error when creating "pod.yaml": pods "nginx" is forbidden: exceeded quota: my-rq, requested: limits.cpu=3,limits.memory=4Gi,requests.cpu=2,requests.memory=3Gi, used: limits.cpu=0,limits.memory=0,requests.cpu=0,requests.memory=0, limited: limits.cpu=2,limits.memory=2Gi,requests.cpu=1,requests.memory=1Gi

Create a pod with resource requests cpu=0.5, memory=1Gi and limits cpu=1, memory=2Gi in namespace one

show 

vi pod2.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
  namespace: one
spec:
  containers:
  - image: nginx
    name: nginx
    resources:
      requests:
        memory: "1Gi"
        cpu: "0.5"
      limits:
        memory: "2Gi"
        cpu: "1"
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}
kubectl create -f pod2.yaml

Show the ResourceQuota usage in namespace one

kubectl get resourcequota -n one
NAME    AGE   REQUEST                                          LIMIT
my-rq   10m   requests.cpu: 500m/1, requests.memory: 1Gi/1Gi   limits.cpu: 1/2, limits.memory: 2Gi/2Gi

Secrets

kubernetes.io > Documentation > Concepts > Configuration > Secrets

kubernetes.io > Documentation > Tasks > Inject Data Into Applications > Distribute Credentials Securely Using Secrets

Create a secret called mysecret with the values password=mypass

show 

kubectl create secret generic mysecret --from-literal=password=mypass

Create a secret called mysecret2 that gets key/value from a file

Create a file called username with the value admin:

echo -n admin > username
show 

kubectl create secret generic mysecret2 --from-file=username

Get the value of mysecret2

show 

kubectl get secret mysecret2 -o yaml
echo -n YWRtaW4= | base64 -d # on MAC it is -D, which decodes the value and shows 'admin'

Alternative using --jsonpath:

kubectl get secret mysecret2 -o jsonpath='{.data.username}' | base64 -d  # on MAC it is -D

Alternative using --template:

kubectl get secret mysecret2 --template '{{.data.username}}' | base64 -d  # on MAC it is -D

Alternative using jq:

kubectl get secret mysecret2 -o json | jq -r .data.username | base64 -d  # on MAC it is -D

Create an nginx pod that mounts the secret mysecret2 in a volume on path /etc/foo

show 

kubectl run nginx --image=nginx --restart=Never -o yaml --dry-run=client > pod.yaml
vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  volumes: # specify the volumes
  - name: foo # this name will be used for reference inside the container
    secret: # we want a secret
      secretName: mysecret2 # name of the secret - this must already exist on pod creation
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    volumeMounts: # our volume mounts
    - name: foo # name on pod.spec.volumes
      mountPath: /etc/foo #our mount path
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}
kubectl create -f pod.yaml
kubectl exec -it nginx -- /bin/bash
ls /etc/foo  # shows username
cat /etc/foo/username # shows admin

Delete the pod you just created and mount the variable 'username' from secret mysecret2 onto a new nginx pod in env variable called 'USERNAME'

show 

kubectl delete po nginx
kubectl run nginx --image=nginx --restart=Never -o yaml --dry-run=client > pod.yaml
vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    env: # our env variables
    - name: USERNAME # asked name
      valueFrom:
        secretKeyRef: # secret reference
          name: mysecret2 # our secret's name
          key: username # the key of the data in the secret
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}
kubectl create -f pod.yaml
kubectl exec -it nginx -- env | grep USERNAME | cut -d '=' -f 2 # will show 'admin'

Create a Secret named 'ext-service-secret' in the namespace 'secret-ops'. Then, provide the key-value pair API_KEY=LmLHbYhsgWZwNifiqaRorH8T as literal.

show 

export ns="-n secret-ops"
export do="--dry-run=client -oyaml"
k create secret generic ext-service-secret --from-literal=API_KEY=LmLHbYhsgWZwNifiqaRorH8T $ns $do > sc.yaml
k apply -f sc.yaml

Consuming the Secret. Create a Pod named 'consumer' with the image 'nginx' in the namespace 'secret-ops' and consume the Secret as an environment variable. Then, open an interactive shell to the Pod, and print all environment variables.

show 

export ns="-n secret-ops"
export do="--dry-run=client -oyaml"
k run consumer --image=nginx $ns $do > nginx.yaml
vi nginx.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: consumer
  name: consumer
  namespace: secret-ops
spec:
  containers:
  - image: nginx
    name: consumer
    resources: {}
    env:
    - name: API_KEY
      valueFrom:
        secretKeyRef:
          name: ext-service-secret
          key: API_KEY
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}
k exec -it $ns consumer -- /bin/sh
#env

Create a Secret named 'my-secret' of type 'kubernetes.io/ssh-auth' in the namespace 'secret-ops'. Define a single key named 'ssh-privatekey', and point it to the file 'id_rsa' in this directory.

show 

#Tips, export to variable
export do="--dry-run=client -oyaml"
export ns="-n secret-ops"

#if id_rsa file didn't exist.
ssh-keygen

k create secret generic my-secret $ns --type="kubernetes.io/ssh-auth" --from-file=ssh-privatekey=id_rsa $do > sc.yaml
k apply -f sc.yaml

Create a Pod named 'consumer' with the image 'nginx' in the namespace 'secret-ops', and consume the Secret as Volume. Mount the Secret as Volume to the path /var/app with read-only access. Open an interactive shell to the Pod, and render the contents of the file.

show 

#Tips, export to variable
export ns="-n secret-ops"
export do="--dry-run=client -oyaml"
k run consumer --image=nginx $ns $do > nginx.yaml
vi nginx.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: consumer
  name: consumer
  namespace: secret-ops
spec:
  containers:
    - image: nginx
      name: consumer
      resources: {}
      volumeMounts:
        - name: foo
          mountPath: "/var/app"
          readOnly: true
  volumes:
    - name: foo
      secret:
        secretName: my-secret
        optional: true
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}
k exec -it $ns consumer -- /bin/sh
# cat /var/app/ssh-privatekey
# exit

ServiceAccounts

kubernetes.io > Documentation > Tasks > Configure Pods and Containers > Configure Service Accounts for Pods

See all the service accounts of the cluster in all namespaces

show 

kubectl get sa --all-namespaces

Alternatively

kubectl get sa -A

Create a new serviceaccount called 'myuser'

show 

kubectl create sa myuser

Alternatively:

# let's get a template easily
kubectl get sa default -o yaml > sa.yaml
vim sa.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: myuser
kubectl create -f sa.yaml

Create an nginx pod that uses 'myuser' as a service account

show 

kubectl run nginx --image=nginx --restart=Never -o yaml --dry-run=client > pod.yaml
vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  serviceAccountName: myuser # we use pod.spec.serviceAccountName
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

or

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  serviceAccount: myuser # we use pod.spec.serviceAccount
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}
kubectl create -f pod.yaml
kubectl describe pod nginx # will see that a new secret called myuser-token-***** has been mounted

Generate an API token for the service account 'myuser'

show 

kubectl create token myuser