What is ConfigMap in Kubernetes ?

1. What is a ConfigMap in Kubernetes?

A ConfigMap in Kubernetes is an API object used to store non-sensitive configuration data as key-value pairs.

i)               Storage: key-value pairs stored in Kubernetes’ etcd datastore.

ii)              Management: Handled by the Kubernetes API server.

iii)             Access: Managed via kubectl CLI or Kubernetes API.

iv)             ConfigMaps in Kubernetes separate configuration from application code, making applications more portable, reusable, and flexible.

v)              The length of the key should not be more than 1MB.

i)               NameSpace A pods cannot use confiMaps of Namespace B.

ii)              Pods will use the config map of the namespace in which they are created and cannot use any other namespace config map.

2. ConfigMaps can be created in two ways.

i) Imperative way:- Create by command line.

ii) Declarative way:- Create by yaml file.

1). Imperative. :-

Literal:

i) Single key pairs.

# kubectl create configmap <Name> --from-literal=<key>=<value>

ii) Multiple key pairs

# kubectl create configmap <Name> --from-literal=<key1>=<value1>  --from-literal=<key2>=<value2>  

iii) From File/Directory: Load configuration from files or folders.

# kubectl create configmap <Name>  --from-file=<FileName>

# kubectl create configmap <Name>  --from-file=<DirectoryName/>

2). Declarative:-

i) Inline YAML: Define directly in YAML manifests.

3. How to Check If ConfigMap Data Exceeds 1MB.

# kubectl get configmap configmap-name -o json | jq '.data | map_values(length)'

{

  "name_key": 12

}

12 bytes  

4. How to create ConfigMap.

Imperative and declarative.

1). Imperative:-

Literal:

a) Create a Single key pairs

 # kubectl create configmap <Name> --from-literal=<key>=<value>

# kubectl get cm

# kubectl describe cm configmap-test

b) ConfigMap use in the yaml file.

# vim configmap-1.yaml

apiVersion: v1

kind: Pod

metadata:

  name: configmap-demo-1

spec:

  containers:

  - name: demo-container

    image: nginx

    envFrom:

    - configMapRef:

       name: configmap-test

# kubectl exec -it configmap-demo-1 -- printenv

a) How to create the  Multiple key pairs ?

# kubectl create configmap <Name> --from-literal=<key1>=<value1>  --from-literal=<key2>=<value2>  

# kubectl create configmap configmap-test --from-literal=conf_Name=first-test --from-literal=conf_Name2=second-test

# kubectl describe cm configmap-test

 

b) How to use a single key in the yaml file.

# vim  configmap-2.yaml

apiVersion: v1

kind: Pod

metadata:

  name: configmap-demo-2

spec:

  containers:

  - name: demo-container

    image: nginx

    env:

    - name: testing

      valueFrom:  

        configMapKeyRef:  

          name: configmap-test

          key: conf_Name2

# kubectl exec -it configmap-demo-2 -- printenv 

a) From File/Directory: Load configuration from files or folders.

# kubectl create configmap <Name>  --from-file=<FileName>

# kubectl create configmap <Name>  --from-file=<DirectoryName/>

# vim data-file

username="shashikant"

password="123456

# kubectl create configmap configmap-3 --from-file=data-file

b) How to mount the data-file.txt file in the yaml file.

# vim configmap-3.yaml

apiVersion: v1

kind: Pod

metadata:

  name: configmap-demo-3

spec:

  containers:

  - name: demo-container

    image: nginx

    volumeMounts:

      - name: config

        mountPath: /etc/config

  volumes:

  - name: config

    configMap:

      name: configmap-3

# kubectl apply -f configmap-3.yaml

# kubectl exec -it configmap-demo-3 -- bash

2. Declarative:-

a) Inline YAML: Define directly in YAML manifests.

# vim configmap.yaml

apiVersion: v1

kind: ConfigMap

metadata:

  name: inline-config

data:

  app_name: myapp

  app_version: "1.0"

  database_url: jdbc:mysql://localhost:3306/mydb

 

How to edit configMaps.

Imperative:-

# kubectl edit configmap  <configmap-Name>

or

Declarative:-

a) Create a yaml file then edit and apply.

# kubectl get configmap configmap-test -o yaml > configmap.yaml

# vim configmap.yaml

apiVersion: v1

kind: ConfigMap

metadata:

  name: configmap-test

  namespace: default

data:

  conf_Name1: first-test1

  conf_Name2: second-test2

# kubectl apply -f configmap.yaml

How to Delete configMaps.

# kubectl delete cm <configmap-Name>

# kubectl delete -f configmap.yaml

ConfigMap vs Secrets:-

Feature	ConfigMap	Secrets
Purpose	Stores non-sensitive configuration data	Stores sensitive or confidential information
Data Encryption	Data is not encrypted	Data is encrypted
Use Cases	Storing environment variables, configuration files, etc.	Storing sensitive data like passwords, API keys, certificates
Access Control	Accessible to all pods within the cluster	Restricted access based on RBAC policies
Kubernetes API	Kubernetes API object of type ConfigMap	Kubernetes API object of type Secret
Visibility	Configurations are visible in plain text	Encrypted data is not visible in plain text
Usage	Suitable for non-sensitive data that needs to be shared	Suitable for sensitive data that requires encryption