I have a configmap where I have defined the following key-value mapping in the data section:
apiVersion: v1
kind: ConfigMap
metadata:
namespace: test
name: test-config
data:
TEST: "CONFIGMAP_VALUE"then in the definition of my container (in the deployment / statefulset manifest) I have the following:
env:
- name: TEST
value: "ANOTHER_VALUE"
envFrom:
- configMapRef:
name: test-configWhen doing this I was expecting that the value from the configmap (TEST="CONFIGMAP_VALUE") will override the (default) value specified in the container spec (TEST="ANOTHER_VALUE"), but this is not the case (TEST always gets the value from the container spec). I couldn't find any relevant documentation about this - is it possible to achieve such env variable value overriding?
From Kubernetes api refernece : https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.13/#container-v1-core
envFrom: List of sources to populate environment variables in the container. The keys defined within a source must be a C_IDENTIFIER. All invalid keys will be reported as an event when the container is starting. When a key exists in multiple sources, the value associated with the last source will take precedence. Values defined by an Env with a duplicate key will take precedence. Cannot be updated.
So above clearly states the env will take precedence than envFrom.
When a key exists in multiple sources, the value associated with the last source will take precedence.
So, for overriding see below:
apiVersion: v1
kind: ConfigMap
metadata:
namespace: default
name: test-config
data:
TEST: "CONFIGMAP_VALUE"
---
apiVersion: v1
kind: Pod
metadata:
name: busy
namespace: default
spec:
containers:
- name: busybox
image: busybox
env:
- name: TEST
value: "DEFAULT_VAULT"
- name: TEST
valueFrom:
configMapKeyRef:
name: test-config
key: TEST
command:
- "sh"
- "-c"
- >
while true; do
echo "$(TEST)";
sleep 3600;
doneCheck:
kubectl logs busy -n default
CONFIGMAP_VALUE