ConfigMaps allow you to decouple configuration artifacts from image content to keep containerized applications portable. This page provides a series of usage examples demonstrating how to create ConfigMaps and configure Pods using data stored in ConfigMaps.
You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:
To check the version, enterkubectl version. You can use either kubectl create configmap or a ConfigMap generator in kustomization.yaml to create a ConfigMap. Note that kubectl starts to support kustomization.yaml since 1.14.
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 name of a ConfigMap object must be a valid DNS subdomain name.
When you are creating a ConfigMap based on a file, the key in the <data-source> defaults to the basename of the file, and the value defaults to the file content.
You can use kubectl describe or kubectl get to retrieve information about a ConfigMap.
You can use kubectl create configmap to create a ConfigMap from multiple files in the same directory. When you are creating a ConfigMap based on a directory, kubectl identifies files whose basename is a valid key in the directory and packages each of those files into the new ConfigMap. Any directory entries except regular files are ignored (e.g. subdirectories, symlinks, devices, pipes, etc).
For example:
# Create the local directory mkdir -p configure-pod-container/configmap/ # Download the sample files into `configure-pod-container/configmap/` directory 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/
The above command packages each file, in this case, game.properties and ui.properties in the configure-pod-container/configmap/ directory into the game-config ConfigMap. You can display details of the ConfigMap using the following command:
kubectl describe configmaps game-config
The output is similar to this:
Name: game-config
Namespace: default
Labels: <none>
Annotations: <none>
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
The game.properties and ui.properties files in the configure-pod-container/configmap/ directory are represented in the data section of the ConfigMap.
kubectl get configmaps game-config -o yaml
The output is similar to this:
apiVersion: v1
kind: ConfigMap
metadata:
creationTimestamp: 2016-02-18T18:52:05Z
name: game-config
namespace: default
resourceVersion: "516"
uid: b4952dc3-d670-11e5-8cd0-68f728db1985
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
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=configure-pod-container/configmap/game.properties
would produce the following ConfigMap:
kubectl describe configmaps game-config-2
where the output is similar to this:
Name: game-config-2
Namespace: default
Labels: <none>
Annotations: <none>
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
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=configure-pod-container/configmap/game.properties --from-file=configure-pod-container/configmap/ui.properties
You can display details of the game-config-2 ConfigMap using the following command:
kubectl describe configmaps game-config-2
The output is similar to this:
Name: game-config-2
Namespace: default
Labels: <none>
Annotations: <none>
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
When kubectl creates a ConfigMap from inputs that are not ASCII or UTF-8, the tool puts these into the binaryData field of the ConfigMap, and not in data. Both text and binary data sources can be combined in one ConfigMap. If you want to view the binaryData keys (and their values) in a ConfigMap, you can run kubectl get configmap -o jsonpath='{.binaryData}' <name>.
Use the option --from-env-file to create a ConfigMap from an env-file, for example:
# Env-files contain a list of environment variables. # These syntax rules apply: # Each line in an env file has to be in VAR=VAL format. # Lines beginning with # (i.e. comments) are ignored. # Blank lines are ignored. # There is no special handling of quotation marks (i.e. they will be part of the ConfigMap value)). # Download the sample files into `configure-pod-container/configmap/` directory wget https://kubernetes.io/examples/configmap/game-env-file.properties -O configure-pod-container/configmap/game-env-file.properties # The env-file `game-env-file.properties` looks like below cat configure-pod-container/configmap/game-env-file.properties enemies=aliens lives=3 allowed="true" # This comment and the empty line above it are ignored
kubectl create configmap game-config-env-file \
--from-env-file=configure-pod-container/configmap/game-env-file.properties
would produce the following ConfigMap:
kubectl get configmap game-config-env-file -o yaml
where the output is similar to this:
apiVersion: v1 kind: ConfigMap metadata: creationTimestamp: 2017-12-27T18:36:28Z name: game-config-env-file namespace: default resourceVersion: "809965" uid: d9d1ca5b-eb34-11e7-887b-42010a8002b8 data: allowed: '"true"' enemies: aliens lives: "3"
--from-env-file multiple times to create a ConfigMap from multiple data sources, only the last env-file is used. The behavior of passing --from-env-file multiple times is demonstrated by:
# Download the sample files into `configure-pod-container/configmap/` directory
wget https://kubernetes.io/examples/configmap/ui-env-file.properties -O configure-pod-container/configmap/ui-env-file.properties
# Create the configmap
kubectl create configmap config-multi-env-files \
--from-env-file=configure-pod-container/configmap/game-env-file.properties \
--from-env-file=configure-pod-container/configmap/ui-env-file.properties
would produce the following ConfigMap:
kubectl get configmap config-multi-env-files -o yaml
where the output is similar to this:
apiVersion: v1 kind: ConfigMap metadata: creationTimestamp: 2017-12-27T18:38:34Z name: config-multi-env-files namespace: default resourceVersion: "810136" uid: 252c4572-eb35-11e7-887b-42010a8002b8 data: color: purple how: fairlyNice textmode: "true"
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=configure-pod-container/configmap/game.properties
would produce the following ConfigMap:
kubectl get configmaps game-config-3 -o yaml
where the output is similar to this:
apiVersion: v1
kind: ConfigMap
metadata:
creationTimestamp: 2016-02-18T18:54:22Z
name: game-config-3
namespace: default
resourceVersion: "530"
uid: 05f8da22-d671-11e5-8cd0-68f728db1985
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
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
The output is similar to this:
apiVersion: v1 kind: ConfigMap metadata: creationTimestamp: 2016-02-18T19:14:38Z name: special-config namespace: default resourceVersion: "651" uid: dadce046-d673-11e5-8cd0-68f728db1985 data: special.how: very special.type: charm
kubectl supports kustomization.yaml since 1.14. You can also create a ConfigMap from generators and then apply it to create the object on the Apiserver. The generators should be specified in a kustomization.yaml inside a directory.
For example, to generate a ConfigMap from files configure-pod-container/configmap/game.properties
# Create a kustomization.yaml file with ConfigMapGenerator cat <<EOF >./kustomization.yaml configMapGenerator: - name: game-config-4 files: - configure-pod-container/configmap/game.properties EOF
Apply the kustomization directory to create the ConfigMap object.
kubectl apply -k . configmap/game-config-4-m9dm2f92bt created
You can check that the ConfigMap was created like this:
kubectl get configmap
NAME DATA AGE
game-config-4-m9dm2f92bt 1 37s
kubectl describe configmaps/game-config-4-m9dm2f92bt
Name: game-config-4-m9dm2f92bt
Namespace: default
Labels: <none>
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","data":{"game.properties":"enemies=aliens\nlives=3\nenemies.cheat=true\nenemies.cheat.level=noGoodRotten\nsecret.code.p...
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
Events: <none>
Note that the generated ConfigMap name has a suffix appended by hashing the contents. This ensures that a new ConfigMap is generated each time the content is modified.
You can define a key other than the file name to use in the ConfigMap generator. For example, to generate a ConfigMap from files configure-pod-container/configmap/game.properties with the key game-special-key
# Create a kustomization.yaml file with ConfigMapGenerator cat <<EOF >./kustomization.yaml configMapGenerator: - name: game-config-5 files: - game-special-key=configure-pod-container/configmap/game.properties EOF
Apply the kustomization directory to create the ConfigMap object.
kubectl apply -k . configmap/game-config-5-m67dt67794 created
To generate a ConfigMap from literals special.type=charm and special.how=very, you can specify the ConfigMap generator in kustomization.yaml as
# Create a kustomization.yaml file with ConfigMapGenerator cat <<EOF >./kustomization.yaml configMapGenerator: - name: special-config-2 literals: - special.how=very - special.type=charm EOF
Apply the kustomization directory to create the ConfigMap object.
kubectl apply -k . configmap/special-config-2-c92b5mmcf2 created
Define an environment variable as a key-value pair in a ConfigMap:
kubectl create configmap special-config --from-literal=special.how=very
Assign the special.how value defined in the ConfigMap to the SPECIAL_LEVEL_KEY environment variable in the Pod specification.
pods/pod-single-configmap-env-variable.yaml
Create the Pod:
kubectl create -f https://kubernetes.io/examples/pods/pod-single-configmap-env-variable.yaml
Now, the Pod's output includes environment variable SPECIAL_LEVEL_KEY=very.
As with the previous example, create the ConfigMaps first.
configmap/configmaps.yaml
Create the ConfigMap:
kubectl create -f https://kubernetes.io/examples/configmap/configmaps.yaml
Define the environment variables in the Pod specification.
pods/pod-multiple-configmap-env-variable.yaml
Create the Pod:
kubectl create -f https://kubernetes.io/examples/pods/pod-multiple-configmap-env-variable.yaml
Now, the Pod's output includes environment variables SPECIAL_LEVEL_KEY=very and LOG_LEVEL=INFO.
Create a ConfigMap containing multiple key-value pairs.
configmap/configmap-multikeys.yaml
Create the ConfigMap:
kubectl create -f https://kubernetes.io/examples/configmap/configmap-multikeys.yaml
envFrom to define all of the ConfigMap's data as container environment variables. The key from the ConfigMap becomes the environment variable name in the Pod.pods/pod-configmap-envFrom.yaml
Create the Pod:
kubectl create -f https://kubernetes.io/examples/pods/pod-configmap-envFrom.yaml
Now, the Pod's output includes environment variables SPECIAL_LEVEL=very and SPECIAL_TYPE=charm.
You can use ConfigMap-defined environment variables in the command and args of a container using the $(VAR_NAME) Kubernetes substitution syntax.
For example, the following Pod specification
pods/pod-configmap-env-var-valueFrom.yaml
created by running
kubectl create -f https://kubernetes.io/examples/pods/pod-configmap-env-var-valueFrom.yaml
produces the following output in the test-container container:
very charm
As explained in Create ConfigMaps from files, when you create a ConfigMap using --from-file, the filename becomes a key stored in the data section of the ConfigMap. The file contents become the key's value.
The examples in this section refer to a ConfigMap named special-config, shown below.
configmap/configmap-multikeys.yaml
Create the ConfigMap:
kubectl create -f https://kubernetes.io/examples/configmap/configmap-multikeys.yaml
Add the ConfigMap name under the volumes section of the Pod specification. This adds the ConfigMap data to the directory specified as volumeMounts.mountPath (in this case, /etc/config). The command section lists directory files with names that match the keys in ConfigMap.
pods/pod-configmap-volume.yaml
Create the Pod:
kubectl create -f https://kubernetes.io/examples/pods/pod-configmap-volume.yaml
When the pod runs, the command ls /etc/config/ produces the output below:
SPECIAL_LEVEL SPECIAL_TYPE
/etc/config/ directory, they will be deleted. Use the path field to specify the desired file path for specific ConfigMap items. In this case, the SPECIAL_LEVEL item will be mounted in the config-volume volume at /etc/config/keys.
pods/pod-configmap-volume-specific-key.yaml
Create the Pod:
kubectl create -f https://kubernetes.io/examples/pods/pod-configmap-volume-specific-key.yaml
When the pod runs, the command cat /etc/config/keys produces the output below:
very
/etc/config/ directory will be deleted. You can project keys to specific paths and specific permissions on a per-file basis. The Secrets user guide explains the syntax.
A ConfigMap reference may be marked "optional". If the ConfigMap is non-existent, the mounted volume will be empty. If the ConfigMap exists, but the referenced key is non-existent the path will be absent beneath the mount point.
When a mounted ConfigMap is updated, the projected content is eventually updated too. This applies in the case where an optionally referenced ConfigMap comes into existence after a pod has started.
Kubelet checks whether the mounted ConfigMap is fresh on every periodic sync. However, it uses its local TTL-based cache for getting the current value of the ConfigMap. As a result, the total delay from the moment when the ConfigMap is updated to the moment when new keys are projected to the pod can be as long as kubelet sync period (1 minute by default) + TTL of ConfigMaps cache (1 minute by default) in kubelet. You can trigger an immediate refresh by updating one of the pod's annotations.
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.
/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.
apiVersion: v1
kind: ConfigMap
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
You must create a ConfigMap before referencing it in a Pod specification (unless you mark the ConfigMap as "optional"). If you reference a ConfigMap that doesn't exist, the Pod won't start. Likewise, references to keys that don't exist in the ConfigMap will prevent the pod from starting.
If you use envFrom to define environment variables from ConfigMaps, keys that are considered invalid will be skipped. The pod will be allowed to start, but the invalid names will be recorded in the event log (InvalidVariableNames). The log message lists each skipped key. For example:
kubectl get events
The output is similar to this:
LASTSEEN FIRSTSEEN COUNT NAME KIND SUBOBJECT TYPE REASON SOURCE MESSAGE
0s 0s 1 dapi-test-pod Pod Warning InvalidEnvironmentVariableNames {kubelet, 127.0.0.1} Keys [1badkey, 2alsobad] from the EnvFrom configMap default/myconfig were skipped since they are considered invalid environment variable names.
ConfigMaps reside in a specific Namespace. A ConfigMap can only be referenced by pods residing in the same namespace.
You can't use ConfigMaps for static pods, because the Kubelet does not support this.
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https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap