Configmaps

Introduction

  • used to store key value pairs

  • allows portability of containerised applications

1. Configmaps can be created from

  • files

  • directories

  • literal values

2. General syntax

kubectl create configmap <map-name> <data-source>

  • map-name is name of configmap you want to assign

  • data-source is the file,directory or literal value

3.Creating configmaps from directory

  • let's see an example
mkdir -p configure-pod-container/configmap/kubectl/
wget https://k8s.io/docs/tasks/configure-pod-container/configmap/kubectl/game.properties -o configure-pod-container/configmap/kubectl/game.properties
wget https://k8s.io/docs/tasks/configure-pod-container/configmap/kubectl/ui.properties -o configure-pod-container/configmap/kubectl/ui.properties
kubectl create configmap game-config --from-file=configure-pod-container/configmap/kubectl/

hadoop@k8s-00:~$ kubectl create configmap game-config --from-file=configure-pod-container/configmap/kubectl/
configmap "game-config" created

  • where name of configmap is game-config

  • and data-source is the two files in the directory 

hadoop@k8s-00:~/configure-pod-container/configmap/kubectl$ tree
.
├── game.properties
└── ui.properties

0 directories, 2 files
  • let's describe the configmap
Data
====
game.properties:
----
--2018-06-18 13:56:30--  https://k8s.io/docs/tasks/configure-pod-container/configmap/kubectl/game.properties
Resolving k8s.io (k8s.io)... 23.236.58.218
Connecting to k8s.io (k8s.io)|23.236.58.218|:443... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://kubernetes.io/docs/tasks/configure-pod-container/configmap/kubectl/game.properties [following]
--2018-06-18 13:56:31--  https://kubernetes.io/docs/tasks/configure-pod-container/configmap/kubectl/game.properties
Resolving kubernetes.io (kubernetes.io)... 45.54.44.100
Connecting to kubernetes.io (kubernetes.io)|45.54.44.100|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 157 [application/octet-stream]
Saving to: ‘game.properties’

     0K                                                       100% 4.20M=0s

2018-06-18 13:56:32 (4.20 MB/s) - ‘game.properties’ saved [157/157]


ui.properties:
----
--2018-06-18 13:56:32--  https://k8s.io/docs/tasks/configure-pod-container/configmap/kubectl/ui.properties
Resolving k8s.io (k8s.io)... 23.236.58.218
Connecting to k8s.io (k8s.io)|23.236.58.218|:443... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://kubernetes.io/docs/tasks/configure-pod-container/configmap/kubectl/ui.properties [following]
--2018-06-18 13:56:33--  https://kubernetes.io/docs/tasks/configure-pod-container/configmap/kubectl/ui.properties
Resolving kubernetes.io (kubernetes.io)... 45.54.44.100
Connecting to kubernetes.io (kubernetes.io)|45.54.44.100|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 83 [application/octet-stream]
Saving to: ‘ui.properties’

     0K                                                       100% 2.59M=0s

2018-06-18 13:56:34 (2.59 MB/s) - ‘ui.properties’ saved [83/83]

4. Creating configmaps from files

hadoop@k8s-00:~$ kubectl create configmap game-config-2 --from-file=configure-pod-container/configmap/kubectl/game.properties
configmap "game-config-2" created
  • describe the configmap as follows, having created using a single file only
hadoop@k8s-00:~$ kubectl describe configmaps game-config-2
Name:         game-config-2
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
game.properties:
  • --from-file argument can be passed multiple times as follows
kubectl create configmap game-config-3 --from-file=configure-pod-container/configmap/kubectl/game.properties --from-file=configure-pod-container/configmap/kubectl/ui.properties

hadoop@k8s-00:~$ kubectl create configmap game-config-3 --from-file=configure-pod-container/configmap/kubectl/game.properties --from-file=configure-pod-container/configmap/kubectl/ui.properties
configmap "game-config-3" created
  • describe the configmap
Data
====
game.properties:
----
--2018-06-18 13:56:30--  https://k8s.io/docs/tasks/configure-pod-container/configmap/kubectl/game.properties
Resolving k8s.io (k8s.io)... 23.236.58.218
Connecting to k8s.io (k8s.io)|23.236.58.218|:443... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://kubernetes.io/docs/tasks/configure-pod-container/configmap/kubectl/game.properties [following]
--2018-06-18 13:56:31--  https://kubernetes.io/docs/tasks/configure-pod-container/configmap/kubectl/game.properties
Resolving kubernetes.io (kubernetes.io)... 45.54.44.100
Connecting to kubernetes.io (kubernetes.io)|45.54.44.100|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 157 [application/octet-stream]
Saving to: ‘game.properties’

     0K                                                       100% 4.20M=0s

2018-06-18 13:56:32 (4.20 MB/s) - ‘game.properties’ saved [157/157]


ui.properties:
----
--2018-06-18 13:56:32--  https://k8s.io/docs/tasks/configure-pod-container/configmap/kubectl/ui.properties
Resolving k8s.io (k8s.io)... 23.236.58.218
Connecting to k8s.io (k8s.io)|23.236.58.218|:443... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://kubernetes.io/docs/tasks/configure-pod-container/configmap/kubectl/ui.properties [following]
--2018-06-18 13:56:33--  https://kubernetes.io/docs/tasks/configure-pod-container/configmap/kubectl/ui.properties
Resolving kubernetes.io (kubernetes.io)... 45.54.44.100
Connecting to kubernetes.io (kubernetes.io)|45.54.44.100|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 83 [application/octet-stream]
Saving to: ‘ui.properties’

     0K                                                       100% 2.59M=0s

2018-06-18 13:56:34 (2.59 MB/s) - ‘ui.properties’ saved [83/83]

5. Creating a configmap using a env file

  • get the env file as follows
wget https://k8s.io/docs/tasks/configure-pod-container/configmap/kubectl/game-env-file.properties -o configure-pod-container/configmap/kubectl/game-env-file.properties
  • edit the properties file with the following content

cat configure-pod-container/configmap/kubectl/game-env-file.properties

enemies=aliens
lives=3
allowed="true"
  • now create the configmap using the env file we just created
hadoop@k8s-00:~$ kubectl create configmap game-config-env-file --from-env-file=configure-pod-container/configmap/kubectl/game-env-file.properties
configmap "game-config-env-file" created
  • describe the configmap as follows
hadoop@k8s-00:~$ kubectl get configmap game-config-env-file -o yaml
apiVersion: v1
data:
  allowed: '"true"'
  enemies: aliens
  lives: "3"
kind: ConfigMap
metadata:
  creationTimestamp: 2018-06-18T14:10:50Z
  name: game-config-env-file
  namespace: default
  resourceVersion: "47999"
  selfLink: /api/v1/namespaces/default/configmaps/game-config-env-file
  uid: 6789c931-7301-11e8-ad8d-76fd51353592
  • when env-files are passed multiple times, only the last env file is considered

6. Create configmaps from literal values

  • in this we define key-value pair from terminal itself as follows
hadoop@k8s-00:~$ kubectl create configmap special-config --from-literal=company.what=admatic --from-literal=skills.how=impeccable
configmap "special-config" created
  • let's describe the configmap as follows
hadoop@k8s-00:~$ kubectl get configmaps special-config -o yaml
apiVersion: v1
data:
  company.what: admatic
  skills.how: impeccable
kind: ConfigMap
metadata:
  creationTimestamp: 2018-06-18T14:16:48Z
  name: special-config
  namespace: default
  resourceVersion: "48468"
  selfLink: /api/v1/namespaces/default/configmaps/special-config
  uid: 3cc94fe0-7302-11e8-ad8d-76fd51353592

7. Define Pod environment variables using ConfigMap data

  • create a pod configmap-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: config
spec:
  containers:
    - name: test-container
      image: k8s.gcr.io/busybox
      command: [ "/bin/sh", "-c", "env" ]
      env:
        - name: SPECIAL_LEVEL_KEY
          valueFrom:
            configMapKeyRef:
              name: special-config
              key: company.what
  restartPolicy: Never
  • run it as follows
hadoop@k8s-00:~$ kubectl create -f configmap-pod.yaml --validate=false
pod "podtestingconfig" created

hadoop@k8s-00:~$ kubectl describe configmaps special-config
Name:         special-config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
company.what:
----
admatic
skills.how:
----
impeccable
Events:  <none>

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