configmap From YAML File

 kubectl create cm cm11 --from-literal=key1=value1 -o yaml

create one yml file

apiVersion: v1

data:

  key1: value1

  key2: value2

  key3: value3

  key4: value4

kind: ConfigMap

metadata:

  name: cm9999

~              kubectl apply -f cm6.yml 

Configmap with env-file

 vi env.sh

variable1=value1

variable2=value2

variable3=value3

variable4=value4

kubectl create cm cm7 --from-env-file=env.sh

kubectl get cm

NAME   DATA   AGE

cm1    0      36m

cm2    0      36m

cm3    1      30m

cm4    2      23m

cm5    3      11m

cm6    1      2m4s

cm7    4      3s

kubectl create cm cm6 --from-file=env.sh

variables name cannot be started from numbers

e.g

355 variables=value1   >> wrong method

Config Map from Files

 create 3 files

echo "file1" > test1.properties

echo "file2" > test2.properties

echo "file3" > test3.properties

kubectl create cm cm5 --from-file=properties/

 $ kubectl describe cm cm5

Name:         cm5

Namespace:    default

Labels:       <none>

Annotations:  <none>

Data

====

test1.properties:

----

file1

test2.properties:

----

file2

test3.properties:

----

file3

Events:  <none>

Config Map From Files

 vi application.properties

**********************************

# database details 

database_ip="192.168.0.4"

database_password="moon"

database_username="abid"

# admin details

username=moonadmin

pasword=moonpassword

************************************

 kubectl create cm cm3 --from-file=application.properties

output:

NAME   DATA   AGE

cm1    0      6m12s

cm2    0      6m6s

cm3    1      12s

controlplane $ kubectl describe cm3

error: the server doesn't have a resource type "cm3"

controlplane $ kubectl describe cm cm3

Name:         cm3

Namespace:    default

Labels:       <none>

Annotations:  <none>

Data

====

application.properties:

----

# database details 

database_ip="192.168.0.4"

database_password="moon"

database_username="abid"

# admin details

username=moonadmin

pasword=moonpassword

secound  example :

vi moon.properties

# database details 

database_ip="192.168.0.4"

database_password="moon"

database_username="abid"

added two config files

kubectl create cm cm4 --from-file=moonabid.properties --from-file=application.properties 

ConfigMap object

 

What is ConfigMap and What is it Used For?

ConfigMaps are APIs that store configuration data in key-value pairs. Their primary function is to keep the configuration separate from the container image. It can represent the entire configuration file or individual properties.

If you are working with Kubernetes, you want to keep your image light and portable. To do this, you should keep the configuration settings separate from the application code. Using ConfigMaps you can add different configuration data on pods to suit the environment they are running in.

For example, you may use the same code with different configuration while in the development, testing or production phase.

How to Create a ConfigMap?

You can create ConfigMaps from files, directories, and literal values.

The basic syntax for creating a ConfigMap is:

kubectl create configmap [configmap_name] [attribute] [source]

Depending on the source, the attribute will be:

• --from file (if the source is a file/directory)
• --from-literal (if the source is a key-value pair)

Option 1: Create ConfigMap Using a YAML File

Use a .yaml file that contains the wanted configuration in the format of key-value pairs to create a ConfigMap:

kubectl create configmap [configmap_name] --from-file [path/to/yaml/file]

For example, to create a ConfigMap under the name example-configmap from the example-configmap.yaml file, you would run:

kubectl create example-configmap --from-file /api/v1/namespace/default/configmaps/example-configmap.yaml

Option 2: Create ConfigMap From Files

Kubernetes allows creating a ConfigMap from one or multiple files in any plaintext format (as long as the files contain key-value pairs).

To create a ConfigMap from a file, use the command:

kubectl create configmap [configmap_name] --from-file [path/to/file]

To create a ConfigMap from multiple files, run:

kubectl create configmap [configmap_name] --from-file [path/to/file1] --from-file [path/to/file2] --from-file [path/to/file3]

Option 3: Create ConfigMap From Directories

You can also create ConfigMaps from directories, that is from all the files within the directory. To do so, use the command:

kubectl create configmap [configmap_name] --from-file [path/to/directory]

Kubectl packages each file from the directory into the new ConfigMap. Only files with basenames that are valid keys are included. Subdirectories and non-regular files are not included in the ConfigMap.

Option 4: Create ConfigMap From Literal Values

You can also create ConfigMaps from literal values, using the --from-literal option.

To do so, follow the basic syntax:

kubectl create configmap [configmap_name] --from-literal [key1]=[value1] --from-literal [key2]=[value]2

See Key-Value Pairs in ConfigMap

To see details from a Kubernetes ConfigMap and the values for keys, use the command:

kubectl get configmaps [configmap_name] -o yaml

The output should display information in the yaml format:

apiVersion: v1
data: 
  key1: value1
  key2: value2
  ...
kind: ConfigMap
metadata:
  creationTimeStamp: ...
  name: example-configmap
  namespace: default
  resourceVersion: ...
  selfLink: /api/v1/namespace/default/configmaps/example-configmap
  uid: ...

Configure Pod to Use ConfigMap

There are two ways you can configure a pod to use a specific ConfigMap:

1. Mounting the ConfigMap as a volume
2. Using environment variables

Mounting ConfigMap as a Volume

Once you have downloaded or created a ConfigMap, you can mount the configuration to the pod by using volumes.

Add a volume section to the to the yaml file of your pod:

volumes:
  - name: config
  configMap
    name: [configmap_name]
    items:
    - key: [key/file_name]
    path: [inside_the_pod]

Once you have added the required content, use the kubectl create command to create the pod with the ConfigMap as the volume.

Use ConfigMap with EnvFrom

ConfigMaps allows you to introduce multiple values through environment variables.

Add the env section to the yaml file of the pod to pull the specified environment variable(s) from a ConfigMap:

env: 
        - name: SPECIAL_LEVEL_KEY
          valueFrom:
            configMapKeyRef:
              name: [configmap_name] 
              key: [key/file_name]

To pull all environment variables from a ConfigMap, add the envFrom section to the yaml file:

envFrom:
  - configMapKeyRef
      name: env-config

Then, use the kubectl create command to create the pod with the specified configuration settings.

Conclusion

This article showed you four different ways how to create ConfigMaps. Additionally, it includes two ways of using Kubernetes ConfigMaps with pods.

kubectl get cm

kubectl create cm cm1 --from-literal=database_ip="192.168.0.4"

                                                               key              =  value 

Name:         cm1

Namespace:    default

Labels:       <none>

Annotations:  <none>

Data

====

database_ip:

----

192.168.0.4

Events:  <none>

ResourceQuota kubernetes (compute based)

vi moon.yml

**************************** 

apiVersion: v1

kind: ResourceQuota

metadata:

  name: pods-medium

spec:

  hard:

    requests.cpu: 0.5

    requests.memory: 500Mi

    limits.cpu: 1

    limits.memory: 1Gi

*************************************

kubectl apply -f moon.yml -n tester

********************************************

create one more pod

vi abid.yml

apiVersion: v1

kind: Pod

metadata:

  name: moon

spec:

  containers:

      - name: web-server

        image: nginx

        resources:

          requests:

            memory: 250Mi

            cpu: 0.1

          limits:

            cpu: 0.5

            memory: 500Mi

kubectl apply -f abid.yml -n tester

kubectl describe ns tester

ResourceQuota Kubernetes object based

 

A resource quota, defined by a ResourceQuota the object provides constraints that limit aggregate resource consumption per namespace. It can limit the number of objects that can be created in a namespace by type, as well as the total amount of computing resources that may be consumed by resources in that namespace.

create one namespace.

kubectl create namespace developer

apiVersion: v1
  kind: ResourceQuota
  metadata:
    name: pods-medium
  spec:
    hard:
      pods: "10"

kubectl apply -f quota.yml -n developer

kubectl describe ns developer

Name:         developer
Labels:       <none>
Annotations:  <none>
Status:       Active

Resource Quotas
 Name:     pods-medium
 Resource  Used  Hard
 --------  ---   ---
 pods      0     10




NameSpace Kubernetes

create namespace

kubectl create namespace test-team

vi moon.yml

*******************************************

 apiVersion: v1

kind: Pod

metadata:

  name: pod1

  namespace: test-team

  labels:

    tier: frontend

spec:

  containers:

     - name: podngin

       image: nginx

0r 

kubectl apply -f moon.yml -n test-team

kubectl get pods -n test-team

**************************************************

kubectl delete 

kubectl delete pod pod1 -n test-team

how to change default NameSpace ?

kubectl config set-context --current --namespace=test-team