I am looking for a way to get environment variable in data section of configmap. In the below yml configuration, I have assigned $NODE_NAME which didn't help me. Is there any way to get this work
apiVersion: v1
kind: ConfigMap
metadata:
name: config
namespace: kube-system
data:
test.conf: |
{
"push": 5,
"test": $NODE_NAME
}
One way to achieve this would be by using the envsubst as following:
$ export NODE_NAME=my-node-name
$ cat << EOF | envsubst | kubectl apply -f-
apiVersion: v1
kind: ConfigMap
metadata:
name: config
namespace: kube-system
data:
test.conf: |
{
"push": 5,
"test": $NODE_NAME
}
EOF
But sth tells me that you want to use this in a pod and populate config with environment variable.
Have a look at this example:
apiVersion: v1
kind: ConfigMap
metadata:
name: config
namespace: kube-system
data:
test.conf: |
{
"push": 5,
"test": $NODE_NAME
}
---
apiVersion: v1
kind: Pod
metadata:
labels:
run: example-pod
name: example-pod
spec:
initContainers:
- args:
- sh
- -c
- cat /test.conf | envsubst > /data/test.conf
image: bhgedigital/envsubst
name: envsubst
env:
- name: NODE_NAME
valueFrom:
fieldRef:
fieldPath: spec.nodeName
volumeMounts:
- mountPath: /data
name: data-volume
- mountPath: /test.conf
subPath: test.conf
name: config-volume
containers:
- image: busybox
name: busybox
args:
- sleep
- "1000"
volumeMounts:
- mountPath: /data
name: data-volume
volumes:
- name: data-volume
emptyDir: {}
- name: config-volume
configMap:
name: config
when you apply the above yaml you can check if the file was substituted correctly as following:
$ kubectl exec -it example-pod -- cat /data/test.conf
{
"push": 5,
"test": minikube
}
As you can see I was testing it in minikube (hence nodeName = minikube in my case)
I don't think it's possible to do in any way that you get out of the box. ConfigMap is just injected into your Pod as it is.
What you can do though is to create an Init Container with a custom script to modify the file injected from ConfigMap. In your script you can use sed or envsubst tools.
