How to fix MountVolume.SetUp failed for volume "config": configmaps "app-config" not found in Kubernetes

KubernetesBEGINNERHIGH

A pod references a ConfigMap that doesn't exist or is in a different namespace. ConfigMaps are namespace-scoped; pods can only access ConfigMaps in their own namespace. Fix by creating the ConfigMap in the correct namespace or marking the reference as optional to allow pod startup.

What this error means

ConfigMaps are Kubernetes configuration objects that store non-sensitive configuration data as key-value pairs. When a pod spec references a ConfigMap for environment variables or volume mounts, Kubernetes expects to find that ConfigMap in the pod's namespace. ConfigMaps are namespace-scoped resources—there is no built-in cross-namespace access mechanism. If the ConfigMap doesn't exist or is in a different namespace, the kubelet cannot mount the config volume or inject the environment variables. The error blocks pod startup entirely unless the ConfigMap reference is marked as optional.

How to fix "MountVolume.SetUp failed for volume "config": configmaps "app-config" not found"

1Verify ConfigMap exists in pod's namespace

List all ConfigMaps in the namespace:

bash

kubectl get configmap -n <pod-namespace>
kubectl describe configmap <configmap-name> -n <pod-namespace>

The ConfigMap name and namespace must match exactly. If missing, move to the next step.

2Check the pod spec for ConfigMap reference

Examine how the pod references the ConfigMap:

bash

kubectl get pod <pod-name> -n <pod-namespace> -o yaml | grep -A10 configMap

Look for:
- volumeMounts[].name and volumes[].configMap.name (for config volumes)
- env[].valueFrom.configMapKeyRef.name (for environment variables)
- envFrom[].configMapRef.name (for bulk env import)

Verify the referenced ConfigMap name matches exactly (case-sensitive).

3Create the missing ConfigMap in the correct namespace

Create the ConfigMap using YAML or kubectl:

Using kubectl with individual values:

bash

kubectl create configmap app-config \
  --from-literal=DATABASE_HOST=localhost \
  --from-literal=DATABASE_PORT=5432 \
  --from-literal=APP_ENV=production \
  -n <pod-namespace>

Using kubectl from a file:

bash

kubectl create configmap app-config \
  --from-file=config.properties \
  -n <pod-namespace>

Using YAML manifest:

yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
  namespace: production
data:
  DATABASE_HOST: localhost
  DATABASE_PORT: "5432"
  APP_ENV: production
  config.ini: |
    [database]
    host=localhost
    port=5432

Apply the manifest:

bash

kubectl apply -f configmap.yaml

Verify creation:

bash

kubectl get configmap -n <pod-namespace>
kubectl describe configmap app-config -n <pod-namespace>

4If ConfigMap is in different namespace, copy or move it

ConfigMaps cannot be referenced across namespaces. You must either copy or move it:

Copy to pod's namespace:

bash

kubectl get configmap <name> -n <source-namespace> -o yaml | \
  sed 's/namespace: <source-namespace>/namespace: <pod-namespace>/' | \
  kubectl apply -f -

Verify:

bash

kubectl get configmap -n <pod-namespace>

Alternative: Move pod to ConfigMap's namespace (if appropriate)

Edit the pod namespace in its manifest and redeploy.

5Verify pod can now access the ConfigMap

After creating the ConfigMap, the pod should start automatically:

bash

kubectl get pod <pod-name> -n <pod-namespace>
kubectl describe pod <pod-name> -n <pod-namespace>

Pod status should transition from Pending to Running. Check logs:

bash

kubectl logs <pod-name> -n <pod-namespace>

Verify ConfigMap environment variables were injected:

bash

kubectl exec <pod-name> -n <pod-namespace> -- env | grep -i config

6Mark ConfigMap reference as optional if appropriate

If ConfigMap is optional (not critical for startup), mark it as optional to allow pod startup even if ConfigMap is missing:

For environment variables:

yaml

env:
- name: CONFIG_SETTING
  valueFrom:
    configMapKeyRef:
      name: app-config
      key: config-setting
      optional: true  # Pod starts even if ConfigMap or key is missing

For bulk import:

yaml

envFrom:
- configMapRef:
    name: app-config
    optional: true

For volume mounts:

yaml

volumes:
- name: config
  configMap:
    name: app-config
    optional: true  # Mount proceeds even if ConfigMap is missing

When optional is true, the pod starts without the ConfigMap data. Environment variables won't be set, and volume mount paths may be empty.

7Check volume mount and environment variable names

Ensure ConfigMap keys match what the application expects:

View ConfigMap keys:

bash

kubectl get configmap app-config -n <pod-namespace> -o yaml

Verify environment variable names:

bash

kubectl exec <pod-name> -n <pod-namespace> -- env | sort

Check volume mount:

bash

kubectl exec <pod-name> -n <pod-namespace> -- ls -la /etc/config/

If using envFrom, invalid environment variable names (e.g., with hyphens or spaces) are silently skipped. Check pod events:

bash

kubectl describe pod <pod-name> -n <pod-namespace> | grep -A5 Events

How to fix MountVolume.SetUp failed for volume "config": configmaps "app-config" not found in Kubernetes

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How to fix "MountVolume.SetUp failed for volume "config": configmaps "app-config" not found"

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