Lab Information
There are some applications that need to be deployed on Kubernetes cluster and these apps have some pre-requisites where some configurations need to be changed before deploying the app container. Some of these changes cannot be made inside the images so the DevOps team has come up with a solution to use init containers to perform these tasks during deployment. Below is a sample scenario that the team is going to test first.
Create a Deployment named as ic-deploy-devops.
Configure spec as replicas should be 1, labels app should be ic-devops, template's metadata lables app should be the same ic-devops.
The initContainers should be named as ic-msg-devops, use image fedora with latest tag and use command '/bin/bash', '-c' and 'echo Init Done - Welcome to xFusionCorp Industries > /ic/blog'. The volume mount should be named as ic-volume-devops and mount path should be /ic.
Main container should be named as ic-main-devops, use image fedora with latest tag and use command '/bin/bash', '-c' and 'while true; do cat /ic/blog; sleep 5; done'. The volume mount should be named as ic-volume-devops and mount path should be /ic.
Volume to be named as ic-volume-devops and it should be an emptyDir type.
Note: The kubectl utility on jump_host has been configured to work with the kubernetes cluster.
Lab Solutions
Step 1: Create the Deployment YAML File
Create a file named ic-deploy-devops.yaml with the following content:
apiVersion: apps/v1
kind: Deployment
metadata:
name: ic-deploy-devops
spec:
replicas: 1
selector:
matchLabels:
app: ic-devops
template:
metadata:
labels:
app: ic-devops
spec:
initContainers:
- name: ic-msg-devops
image: fedora:latest
command: ['/bin/bash', '-c', 'echo Init Done - Welcome to xFusionCorp Industries > /ic/blog']
volumeMounts:
- name: ic-volume-devops
mountPath: /ic
containers:
- name: ic-main-devops
image: fedora:latest
command: ['/bin/bash', '-c', 'while true; do cat /ic/blog; sleep 5; done']
volumeMounts:
- name: ic-volume-devops
mountPath: /ic
volumes:
- name: ic-volume-devops
emptyDir: {}
Step 2: Apply the Deployment
Deploy the configuration to your Kubernetes cluster:
kubectl apply -f ic-deploy-devops.yaml
Step 3: Verify the Deployment
Check if the deployment was created successfully:
kubectl get deployment ic-deploy-devops
Step 4: Check the Pod Status
Monitor the pod creation and init container execution:
kubectl get pods -l app=ic-devops
Step 5: Verify Init Container Execution
Check the init container logs to ensure it ran successfully:
# Get the pod name first
POD_NAME=$(kubectl get pods -l app=ic-devops -o jsonpath='{.items[0].metadata.name}')
# Check init container logs
kubectl logs $POD_NAME -c ic-msg-devops
Step 6: Verify Main Container Operation
Check the main container logs to see the continuous output:
kubectl logs $POD_NAME -c ic-main-devops
The main container should be printing the message every 5 seconds.
Step 7: Detailed Verification
Let's verify all components are correctly configured:
# Check the deployment details:
kubectl describe deployment ic-deploy-devops
# Check the pod details:
kubectl describe pod $POD_NAME
# Verify the volume mount:
kubectl exec $POD_NAME -c ic-main-devops -- ls -la /ic/
# Check the file content directly:
kubectl exec $POD_NAME -c ic-main-devops -- cat /ic/blog
Output
thor@jumphost ~$ kubectl describe deployment ic-deploy-devops
Name: ic-deploy-devops
Namespace: default
CreationTimestamp: Fri, 31 Oct 2025 13:43:39 +0000
Labels: <none>
Annotations: deployment.kubernetes.io/revision: 1
Selector: app=ic-devops
Replicas: 1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 25% max unavailable, 25% max surge
Pod Template:
Labels: app=ic-devops
Init Containers:
ic-msg-devops:
Image: fedora:latest
Port: <none>
Host Port: <none>
Command:
/bin/bash
-c
echo Init Done - Welcome to xFusionCorp Industries > /ic/blog
Environment: <none>
Mounts:
/ic from ic-volume-devops (rw)
Containers:
ic-main-devops:
Image: fedora:latest
Port: <none>
Host Port: <none>
Command:
/bin/bash
-c
while true; do cat /ic/blog; sleep 5; done
Environment: <none>
Mounts:
/ic from ic-volume-devops (rw)
Volumes:
ic-volume-devops:
Type: EmptyDir (a temporary directory that shares a pod's lifetime)
Medium:
SizeLimit: <unset>
Node-Selectors: <none>
Tolerations: <none>
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet: ic-deploy-devops-68789fbb69 (1/1 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 3m55s deployment-controller Scaled up replica set ic-deploy-devops-68789fbb69 to 1
thor@jumphost ~$ kubectl describe pod $POD_NAME
Name: ic-deploy-devops-68789fbb69-n46fh
Namespace: default
Priority: 0
Service Account: default
Node: kodekloud-control-plane/172.17.0.2
Start Time: Fri, 31 Oct 2025 13:43:39 +0000
Labels: app=ic-devops
pod-template-hash=68789fbb69
Annotations: <none>
Status: Running
IP: 10.244.0.5
IPs:
IP: 10.244.0.5
Controlled By: ReplicaSet/ic-deploy-devops-68789fbb69
Init Containers:
ic-msg-devops:
Container ID: containerd://fda2d6a406793fce4784b97fbd48e04fc4562a26b6153f877bedff8460ffa44e
Image: fedora:latest
Image ID: docker.io/library/fedora@sha256:aa7befe5cfd1f0e062728c16453cd1c479d4134c7b85eac00172f3025ab0d522
Port: <none>
Host Port: <none>
Command:
/bin/bash
-c
echo Init Done - Welcome to xFusionCorp Industries > /ic/blog
State: Terminated
Reason: Completed
Exit Code: 0
Started: Fri, 31 Oct 2025 13:43:46 +0000
Finished: Fri, 31 Oct 2025 13:43:46 +0000
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/ic from ic-volume-devops (rw)
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-mqkwp (ro)
Containers:
ic-main-devops:
Container ID: containerd://dbc7396b61602a895278a5ebf5eb61bc231ef702bd607c39237866dd6c5a5b5a
Image: fedora:latest
Image ID: docker.io/library/fedora@sha256:aa7befe5cfd1f0e062728c16453cd1c479d4134c7b85eac00172f3025ab0d522
Port: <none>
Host Port: <none>
Command:
/bin/bash
-c
while true; do cat /ic/blog; sleep 5; done
State: Running
Started: Fri, 31 Oct 2025 13:43:47 +0000
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/ic from ic-volume-devops (rw)
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-mqkwp (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
ic-volume-devops:
Type: EmptyDir (a temporary directory that shares a pod's lifetime)
Medium:
SizeLimit: <unset>
kube-api-access-mqkwp:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 4m3s default-scheduler Successfully assigned default/ic-deploy-devops-68789fbb69-n46fh to kodekloud-control-plane
Normal Pulling 4m2s kubelet Pulling image "fedora:latest"
Normal Pulled 3m57s kubelet Successfully pulled image "fedora:latest" in 5.558670958s (5.558686183s including waiting)
Normal Created 3m57s kubelet Created container ic-msg-devops
Normal Started 3m56s kubelet Started container ic-msg-devops
Normal Pulling 3m56s kubelet Pulling image "fedora:latest"
Normal Pulled 3m55s kubelet Successfully pulled image "fedora:latest" in 144.822007ms (144.841997ms including waiting)
Normal Created 3m55s kubelet Created container ic-main-devops
Normal Started 3m55s kubelet Started container ic-main-devops
thor@jumphost ~$ kubectl exec $POD_NAME -c ic-main-devops -- ls -la /ic/
total 12
drwxrwxrwx 2 root root 4096 Oct 31 13:43 .
drwxr-xr-x 1 root root 4096 Oct 31 13:43 ..
-rw-r--r-- 1 root root 46 Oct 31 13:43 blog
thor@jumphost ~$ kubectl exec $POD_NAME -c ic-main-devops -- cat /ic/blog
Init Done - Welcome to xFusionCorp Industries
Step 8: Continuous Monitoring
To see the real-time output from the main container:
kubectl logs $POD_NAME -c ic-main-devops -f
Press Ctrl+C to exit the continuous log view.
Explanation of the Solution
Init Container (ic-msg-devops):
Runs before the main container starts
Creates a file /ic/blog with the welcome message
Uses the shared volume ic-volume-devops
Main Container (ic-main-devops):
Starts after the init container completes successfully
Reads the file created by the init container every 5 seconds
Shares the same volume mount
Volume (ic-volume-devops):
emptyDir type creates a temporary directory that survives container restarts
Shared between init container and main container
Data persists for the lifetime of the pod
Workflow:
Init container writes message to file → Init container completes → Main container starts → Main container reads file repeatedly
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