Deployment status and history in Kubernetes - Commands & Configuration

Introduction

When you update your app in Kubernetes, you want to see if the new version is running well and check past updates. Deployment status and history help you track these changes and fix problems quickly.

When you want to confirm that your app update was successful and is running without errors.

When you need to see what changes were made in previous app versions to understand issues.

When you want to roll back to a previous version after a bad update.

When you want to monitor how many times your app has been updated and when.

When you want to check if Kubernetes is still updating your app or if it finished.

Commands

This command shows the current status of the deployment named 'my-app'. It tells you if the update is complete or still in progress.

Terminal

kubectl rollout status deployment/my-app

Expected Output

deployment "my-app" successfully rolled out

This command lists the history of all updates made to the 'my-app' deployment, showing revision numbers and change causes if available.

Terminal

kubectl rollout history deployment/my-app

Expected Output

deployment.apps/my-app

REVISION  CHANGE-CAUSE

1         Initial deployment

2         Updated image to v2

This command shows details of the first revision of the 'my-app' deployment, helping you see what was changed in that update.

Terminal

kubectl rollout history deployment/my-app --revision=1

Expected Output

deployment.apps/my-app with revision #1

Pod Template:

  Containers:

    my-app:

      Image: my-app-image:v1

      Ports:

        - 80/TCP

→

--revision - Shows details for a specific revision number

This command rolls back the 'my-app' deployment to the previous working version if the current update has problems.

Terminal

kubectl rollout undo deployment/my-app

Expected Output

deployment.apps/my-app rolled back

This command shows the current state of the 'my-app' deployment including how many pods are ready and available.

Terminal

kubectl get deployment my-app

Expected Output

NAME     READY   UP-TO-DATE   AVAILABLE   AGE

my-app   3/3     3            3           10m

Key Concept

If you remember nothing else from this pattern, remember: use 'kubectl rollout status' to check if your app update finished successfully and 'kubectl rollout history' to see past changes.

Common Mistakes

Running 'kubectl get pods' only to check deployment status

This shows pod states but not if the deployment update is complete or rolled out correctly.

Use 'kubectl rollout status deployment/my-app' to get accurate deployment update status.

Not specifying the deployment name correctly in commands

Commands fail or show no results if the deployment name is wrong or missing.

Always use the exact deployment name, for example 'my-app', in rollout commands.

Trying to view rollout history without any revisions

If the deployment has never been updated, history will be empty or show only initial deployment.

Make sure the deployment has at least one update before checking history.

Summary

Use 'kubectl rollout status deployment/my-app' to check if your deployment update finished successfully.

Use 'kubectl rollout history deployment/my-app' to see all past updates and their revision numbers.

Use 'kubectl rollout undo deployment/my-app' to roll back to the previous working version if needed.

Practice

1. What does the command kubectl rollout status deployment/myapp do in Kubernetes?

easy

A. It shows if the deployment named 'myapp' is successfully running or still updating.

B. It deletes the deployment named 'myapp' from the cluster.

C. It creates a new deployment named 'myapp'.

D. It lists all pods running in the cluster.

Solution

1. Step 1: Understand the command purpose

   The command kubectl rollout status checks the current status of a deployment rollout.

2. Step 2: Apply to the specific deployment

   Using deployment/myapp targets the deployment named 'myapp' to see if it is running or updating.

3. Final Answer:

   It shows if the deployment named 'myapp' is successfully running or still updating. -> Option A

4. Quick Check:

   Rollout status = Deployment running status [OK]

Hint: Use rollout status to check deployment health quickly [OK]

Common Mistakes:

• Confusing rollout status with deployment creation
• Thinking it deletes or lists pods
• Using wrong resource type after rollout status

2. Which of the following is the correct syntax to view the rollout history of a deployment named 'webapp'?

easy

A. kubectl get rollout history webapp

B. kubectl describe rollout webapp

C. kubectl rollout status deployment/webapp

D. kubectl rollout history deployment/webapp

Solution

1. Step 1: Identify the correct command for rollout history

   The command to view rollout history is kubectl rollout history.

2. Step 2: Use correct resource type and name

   Appending deployment/webapp specifies the deployment named 'webapp'.

3. Final Answer:

   kubectl rollout history deployment/webapp -> Option D

4. Quick Check:

   Rollout history syntax = kubectl rollout history deployment/name [OK]

Hint: Remember: rollout history shows past changes, rollout status shows current state [OK]

Common Mistakes:

• Using 'get' or 'describe' instead of 'rollout history'
• Omitting 'deployment/' prefix
• Confusing rollout status with rollout history

3. Given the command output:

deployment "frontend" successfully rolled out

What command was most likely run to get this output?

medium

A. kubectl get pods -l app=frontend

B. kubectl rollout history deployment/frontend

C. kubectl rollout status deployment/frontend

D. kubectl describe deployment frontend

Solution

1. Step 1: Analyze the output message

   The message says the deployment "frontend" was successfully rolled out, indicating a status check.

2. Step 2: Match output to command

   kubectl rollout status shows this success message, while history or describe commands show different outputs.

3. Final Answer:

   kubectl rollout status deployment/frontend -> Option C

4. Quick Check:

   Success rollout message = rollout status command [OK]

Hint: Success message means rollout status was checked [OK]

Common Mistakes:

• Confusing rollout history output with status output
• Assuming pod listing shows rollout success
• Using describe which shows detailed info, not status message

4. You ran kubectl rollout history deployment/api but got an error: error: deployments.apps "api" not found. What is the most likely cause?

medium

A. The Kubernetes cluster is down.

B. The deployment named 'api' does not exist in the current namespace.

C. You need to add '--all-namespaces' to see the deployment.

D. The command syntax is incorrect; 'rollout history' is invalid.

Solution

1. Step 1: Understand the error message

   The error says deployment "api" not found, meaning Kubernetes can't find that deployment in the current namespace.

2. Step 2: Check command and context

   The command syntax is correct, and cluster down would cause different errors. Missing deployment is the most likely cause.

3. Final Answer:

   The deployment named 'api' does not exist in the current namespace. -> Option B

4. Quick Check:

   Deployment not found error = deployment missing [OK]

Hint: Check deployment name and namespace if 'not found' error appears [OK]

Common Mistakes:

• Assuming syntax error when command is correct
• Forgetting namespace context
• Blaming cluster status without checking deployment

5. You want to rollback your deployment 'backend' to the previous version after a failed update. Which sequence of commands correctly checks the history and rolls back?

hard

A. kubectl rollout history deployment/backendkubectl rollout undo deployment/backend

B. kubectl rollout status deployment/backendkubectl delete deployment/backend

C. kubectl get pods -l app=backendkubectl rollout history deployment/backend

D. kubectl rollout undo deployment/backendkubectl rollout history deployment/backend

Solution

1. Step 1: Check rollout history

   Use kubectl rollout history deployment/backend to see past versions and confirm rollback target.

2. Step 2: Rollback to previous version

   Use kubectl rollout undo deployment/backend to revert to the last successful deployment.

3. Final Answer:

   kubectl rollout history deployment/backend followed by kubectl rollout undo deployment/backend -> Option A

4. Quick Check:

   History then undo = safe rollback steps [OK]

Hint: Always check history before undoing a rollout [OK]

Common Mistakes:

• Deleting deployment instead of rolling back
• Undoing before checking history
• Confusing status command with rollback