7.7 KiB
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Configure Containers Using a ConfigMap |
{% capture overview %}
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.
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{% capture prerequisites %}
- {% include task-tutorial-prereqs.md %}
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{% capture steps %}
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
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{% capture discussion %}
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 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.
{: .note}
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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{% capture whatsnext %}
- See Using ConfigMap Data in Pods.
- Follow a real world example of Configuring Redis using a ConfigMap. {% endcapture %}
{% include templates/task.md %}