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Configure Containers Using a ConfigMap

This page shows you how to configure an application using a ConfigMap.

Before you begin

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

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-2 -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-2
  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
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
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

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