Configure Containers Using a ConfigMap
This page shows you how to configure an application using a ConfigMap. ConfigMaps allow you to decouple configuration artifacts from image content to keep containerized applications portable.
Before you begin
-
You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using Minikube, or you can use one of these Kubernetes playgrounds:
- Katacoda
- Play with Kubernetes
Use kubectl to create a ConfigMap
Use the kubectl create configmap command to create configmaps from directories, files, or literal values:
kubectl create configmap <map-name> <data-source>
where <map-name> is the name you want to assign to the ConfigMap and <data-source> is the directory, file, or literal value to draw the data from.
The data source corresponds to a key-value pair in the ConfigMap, where
- key = the file name or the key you provided on the command line, and
- value = the file contents or the literal value you provided on the command line.
You can use kubectl describe or kubectl get to retrieve information about a ConfigMap. The former shows a summary of the ConfigMap, while the latter returns the full contents of the ConfigMap.
Create ConfigMaps from directories
You can use kubectl create configmap to create a ConfigMap from multiple files in the same directory.
For example:
kubectl create configmap game-config --from-file=docs/user-guide/configmap/kubectl
combines the contents of the docs/user-guide/configmap/kubectl/ directory
ls docs/user-guide/configmap/kubectl/
game.properties
ui.properties
into the following ConfigMap:
kubectl describe configmaps game-config
Name: game-config
Namespace: default
Labels: <none>
Annotations: <none>
Data
====
game.properties: 158 bytes
ui.properties: 83 bytes
The game.properties and ui.properties files in the docs/user-guide/configmap/kubectl/ directory are represented in the data section of the ConfigMap.
kubectl get configmaps game-config -o yaml
apiVersion: v1
data:
game.properties: |
enemies=aliens
lives=3
enemies.cheat=true
enemies.cheat.level=noGoodRotten
secret.code.passphrase=UUDDLRLRBABAS
secret.code.allowed=true
secret.code.lives=30
ui.properties: |
color.good=purple
color.bad=yellow
allow.textmode=true
how.nice.to.look=fairlyNice
kind: ConfigMap
metadata:
creationTimestamp: 2016-02-18T18:52:05Z
name: game-config
namespace: default
resourceVersion: "516"
selfLink: /api/v1/namespaces/default/configmaps/game-config-2
uid: b4952dc3-d670-11e5-8cd0-68f728db1985
Create ConfigMaps from files
You can use kubectl create configmap to create a ConfigMap from an individual file, or from multiple files.
For example,
kubectl create configmap game-config-2 --from-file=docs/user-guide/configmap/kubectl/game.properties
would produce the following ConfigMap:
kubectl describe configmaps game-config-2
Name: game-config-2
Namespace: default
Labels: <none>
Annotations: <none>
Data
====
game.properties: 158 bytes
You can pass in the --from-file argument multiple times to create a ConfigMap from multiple data sources.
kubectl create configmap game-config-2 --from-file=docs/user-guide/configmap/kubectl/game.properties --from-file=docs/user-guide/configmap/kubectl/ui.properties
kubectl describe configmaps game-config-2
Name: game-config-2
Namespace: default
Labels: <none>
Annotations: <none>
Data
====
game.properties: 158 bytes
ui.properties: 83 bytes
Define the key to use when creating a ConfigMap from a file
You can define a key other than the file name to use in the data section of your ConfigMap when using the --from-file argument:
kubectl create configmap game-config-3 --from-file=<my-key-name>=<path-to-file>
where <my-key-name> is the key you want to use in the ConfigMap and <path-to-file> is the location of the data source file you want the key to represent.
For example:
kubectl create configmap game-config-3 --from-file=game-special-key=docs/user-guide/configmap/kubectl/game.properties
kubectl get configmaps game-config-3 -o yaml
apiVersion: v1
data:
game-special-key: |
enemies=aliens
lives=3
enemies.cheat=true
enemies.cheat.level=noGoodRotten
secret.code.passphrase=UUDDLRLRBABAS
secret.code.allowed=true
secret.code.lives=30
kind: ConfigMap
metadata:
creationTimestamp: 2016-02-18T18:54:22Z
name: game-config-3
namespace: default
resourceVersion: "530"
selfLink: /api/v1/namespaces/default/configmaps/game-config-3
uid: 05f8da22-d671-11e5-8cd0-68f728db1985
Create ConfigMaps from literal values
You can use kubectl create configmap with the --from-literal argument to define a literal value from the command line:
kubectl create configmap special-config --from-literal=special.how=very --from-literal=special.type=charm
You can pass in multiple key-value pairs. Each pair provided on the command line is represented as a separate entry in the data section of the ConfigMap.
kubectl get configmaps special-config -o yaml
apiVersion: v1
data:
special.how: very
special.type: charm
kind: ConfigMap
metadata:
creationTimestamp: 2016-02-18T19:14:38Z
name: special-config
namespace: default
resourceVersion: "651"
selfLink: /api/v1/namespaces/default/configmaps/special-config
uid: dadce046-d673-11e5-8cd0-68f728db1985
Understanding ConfigMaps
ConfigMaps allow you to decouple configuration artifacts from image content to keep containerized applications portable. The ConfigMap API resource stores configuration data as key-value pairs. The data can be consumed in pods or provide the configurations for system components such as controllers. ConfigMap is similar to Secrets, but provides a means of working with strings that don’t contain sensitive information. Users and system components alike can store configuration data in ConfigMap.
Note: ConfigMaps should reference properties files, not replace them. Think of the ConfigMap as representing something similar to the a Linux /etc directory and its contents. For example, if you create a Kubernetes Volume from a ConfigMap, each data item in the ConfigMap is represented by an individual file in the volume.
The ConfigMap’s data field contains the configuration data. As shown in the example below, this can be simple – like individual properties defined using --from-literal – or complex – like configuration files or JSON blobs defined using --from-file.
kind: ConfigMap
apiVersion: v1
metadata:
creationTimestamp: 2016-02-18T19:14:38Z
name: example-config
namespace: default
data:
# example of a simple property defined using --from-literal
example.property.1: hello
example.property.2: world
# example of a complex property defined using --from-file
example.property.file: |-
property.1=value-1
property.2=value-2
property.3=value-3
What’s next
- See Using ConfigMap Data in Pods.
- Follow a real world example of Configuring Redis using a ConfigMap.