ConfigMap
What is ConfigMap and when is it used? π€
Think of it as a properties file for your application. For example depending on your application environment (dev, int, prod) you will have a different database url or logging level. So for these kind of things you can use configMap.
The biggest advantage is that, with properties file, every time you modify it you have to rebuild and redeploy your application, whereas if you change configuration in configMap, you just need to restart the application pod/container.
ConfigMap can be used by the application as a set of environmental variable values or as an actual configuration file.
Example ConfigMap with database connection configuration:
apiVersion: v1
kind: ConfigMap
metadata:
name: my-config
data:
db-host: cluster-mysql.database
db-port: 3306
db-name: my-db
The values in this configMap can be used in a following way in your app's pod specification:
apiVersion: v1
kind: Pod
metadata:
name: my-app
spec:
containers:
- name: my-app
image: my-app-image
env:
- name: DB_HOST
valueFrom:
configMapKeyRef:
name: my-config
key: db-host
- name: DB_PORT
valueFrom:
configMapKeyRef:
name: my-config
key: db-port
- name me: DB_NAME
valueFrom:
configMapKeyRef:
name: my-config
key: db-name
Here is an example ConfigMap which creates a configuration file for Mosquitto app:
apiVersion: v1
kind: ConfigMap
metadata:
name: mosquitto-config
data:
mosquitto.conf |
log_dest stout
log_type all
log_timestamp true
listener 9001
In this case we need to mount the ConfigMap as a volume in Kubernetes:
apiVersion: v1
kind: Pod
metadata:
name: mosquitto
spec:
containers:
- name: mosquitto
image: mosquitto-image
volumeMounts:
- name: config-file
mountPath: /mosquitto/config
volumes:
- name: config-file
configMap:
name: mosquitto-config
This config map will produce a file mosquitto.conf
, which then can be mounted into the Mosquitto container under /mosquitto/config
directory.
Secret
Secrets π are also used in these 2 ways. Either as a value for env variables or as a secret file with credentials or a certificate etc mounted into a pod.
So for a better comparison, think of secrets as encrypted configMaps.
Example secret with key-value pairs:
apiVersion: v1
kind: Secret
metadata:
name: my-secret
type: Opaque
data:
db-user: dXNlcg==
db-password: cGFzc3dvcmQ
And you can use it the same way as ConfigMap in your application's configuration file:
apiVersion: v1
kind: Pod
metadata:
name: my-app
spec:
containers:
- name: my-app
image: my-app-image
env:
- name: DB_USER
valueFrom:
secretKeyRef:
name: my-secret
key: db-user
- name: DB_PASSWORD
valueFrom:
secretKeyRef:
name: my-secret
key: db-password
Here is an example secret that creates a file:
apiVersion: v1
kind: Secret
metadata:
name: my-secret
type: Opaque
data:
cacert.pem |
base-64-encoded value of a PEM certificate
And again, just like with ConfigMap, you will need to mount this secret as a volume into the pod to use the cacert.pem file:
apiVersion: v1
kind: Pod
metadata:
name: my-app
spec:
containers:
- name: my-app
image: my-app-image
volumeMounts:
- name: certificate-file
mountPath: /etc/secret
volumes:
- name: certificate-file
configMap:
name: my-secret
The inconvenience with this way of creating a secret for a file is that you will have to base64 encode the file contents and then paste it into the data section.
So an easier alternative way to create secrets from a file is with kubectl command.
Like in the above case, get the cacert.pem
file and execute:
kubectl create secret generic my-secret --from-file=./cacert.pem
Thanks for reading π©π»βπ» and click on β€οΈ or π¦ if you learned something. π€
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