What is a ConfigMap in Kubernetes Part-03

 1. What is a ConfigMap ?  

a) Decouples configuration from pods and components.

b) Stores configuration data as key-value pairs.

              i) configuration files.

              ii) command line arguments.                                                     

              iii) Environment variables.

c) Similar to Secrets but don’t contain sensitive information.

d) You must create a ConfigMap before referencing it in a Pod spec.

configFile/properties file  -- configMap -- used pods.
                                                (yaml/cmd)     (yaml)

2. Create a ConfigMap command. 

# kubectl create configmap  <map-name>   <data-source>

3. Three type of data source.

4. There are two operators used in configmap command.

5. Data source Use Literal :- 

i)  Create configmap a single parameter. (manual parameter defined).

# kubectl create cm firstconfigmap --from-literal=database_ip="192.168.0.21"

ii) Create configmap multiple parameter use literal. (manual parameter defined).

# kubectl create cm secondconfigmap --from-literal=database_ip="192.168.0.21"  --from-literal=database_username="root"  --from-literal=database_password="sagh12"

# kubectl get cm

NAME               DATA   AGE
firstconfigmap     1      3m9s
kube-root-ca.crt   1      42h

NAME :- Created ConfigMap name
DATA :- How many parameter in Configmap file.
AGE :- total create time.

# kubectl describe cm firstconfigmap

How to apply configmap in nginx pods.

# vim firstcontainer.yaml 

# kubectl  apply  -f  firstcontainer.yaml

Verify key variable in container environment.    

# kubectl exec nginxpod -c ngxcontainer -it bash --> for login container

                or

# kubectl exec nginxpod -c ngxcontainer -it env --> for check system variable

6. Create ConfigMaps from directories.

# mkdir -p configure-pod-container/configmap/

# wget https://kubernetes.io/examples/configmap/game.properties -O configure-pod-container/configmap/game.properties

# wget https://kubernetes.io/examples/configmap/ui.properties -O configure-pod-container/configmap/ui.properties

# Create the configmap

# kubectl create configmap game-config --from-file=configure-pod-container/configmap/

# kubectl describe cm game-config

Create a yaml file for directory.

# kubectl get cm game-config -o yaml

7.Creating ConfigMaps from -file.

# curl -OL https://k8s.io/examples/pods/config/redis-config

# cat redis-config

maxmemory 2mb 

maxmemory-policy allkeys-lru 

# kubectl create configmap example-redis-config --from-file=redis-config

Accessing ConfigMaps in Pods. (use both dierctory and file)

# kubectl  apply  -f  first_pod.yaml

# kubectl exec nginxpod -it bash

#  kubectl exec nginxpod -- ls /redis-master  (check file)