Ingress controllers (Nginx, Traefik) in Kubernetes - Commands & Configuration

Introduction

When you run multiple apps inside Kubernetes, you need a way to let users reach them from outside. Ingress controllers like Nginx and Traefik help by managing how external traffic gets routed to your apps safely and easily.

When you want to expose several web apps on the same IP but different URLs or paths.

When you need to manage SSL certificates for your apps automatically.

When you want to control traffic rules like redirects or load balancing inside your cluster.

When you want to monitor and log incoming requests centrally.

When you want to simplify external access without creating many LoadBalancer services.

Config File - ingress.yaml

ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /$2
spec:
  ingressClassName: nginx
  rules:
  - host: example.local
    http:
      paths:
      - path: /app1(/|$)(.*)
        pathType: Prefix
        backend:
          service:
            name: app1-service
            port:
              number: 80
      - path: /app2(/|$)(.*)
        pathType: Prefix
        backend:
          service:
            name: app2-service
            port:
              number: 80

This file defines an Ingress resource that routes traffic based on URL paths to two different services inside the cluster.

metadata.annotations tells Nginx to rewrite the URL path before sending it to the service.

spec.ingressClassName specifies that this Ingress uses the Nginx controller.

spec.rules define the host and paths to route traffic to the right backend services.

Commands

This command creates the Ingress resource in Kubernetes, telling the Ingress controller how to route external traffic to your services.

Terminal

kubectl apply -f ingress.yaml

Expected Output

ingress.networking.k8s.io/example-ingress created

This command checks the status and details of the Ingress resource to confirm it was created and see its rules.

Terminal

kubectl get ingress example-ingress

Expected Output

NAME              CLASS    HOSTS          ADDRESS        PORTS   AGE

example-ingress   nginx    example.local  192.168.99.100 80      10s

This command shows detailed information about the Ingress, including backend services and any events or errors.

Terminal

kubectl describe ingress example-ingress

Expected Output

Name:             example-ingress

Namespace:        default

Address:          192.168.99.100

Default backend:  <none>

Rules:

  Host           Path  Backends

  ----           ----  --------

  example.local

                 /app1(/|$)(.*)   app1-service:80 (10.1.1.10:80)

                 /app2(/|$)(.*)   app2-service:80 (10.1.1.11:80)

Annotations:     nginx.ingress.kubernetes.io/rewrite-target: /$2

Events:

  Type    Reason  Age   From                      Message

  ----    ------  ----  ----                      -------

  Normal  Sync    10s   nginx-ingress-controller  Scheduled for sync

This command verifies that the Nginx Ingress controller pods are running in the cluster namespace where it is installed.

Terminal

kubectl get pods -n ingress-nginx

Expected Output

NAME                                        READY   STATUS    RESTARTS   AGE

nginx-ingress-controller-5d7f9f7d7f-abc12  1/1     Running   0          5m

Key Concept

If you remember nothing else from this pattern, remember: Ingress controllers route external traffic to your Kubernetes services based on rules you define.

Common Mistakes

Not specifying the correct ingressClassName matching the installed controller

The Ingress resource won't be picked up by any controller, so traffic won't route correctly.

Check which ingress controller is installed and use its class name exactly in the Ingress spec.

Forgetting to create or install the Ingress controller before applying Ingress resources

Ingress resources depend on the controller to function; without it, rules have no effect.

Install the Nginx or Traefik Ingress controller first using their official manifests or Helm charts.

Using incorrect path syntax or missing rewrite annotations

Requests may not reach the backend services correctly or cause 404 errors.

Use proper pathType and rewrite-target annotations as per the controller's documentation.

Summary

Create an Ingress resource to define routing rules for external traffic to services.

Use kubectl apply to deploy the Ingress and kubectl get/describe to verify it.

Ensure the Ingress controller (Nginx or Traefik) is installed and running to handle the traffic.

Practice

1. What is the main role of an Ingress controller like Nginx or Traefik in Kubernetes?

easy

A. To monitor pod resource usage

B. To manage Kubernetes cluster nodes

C. To store container images

D. To route external traffic to internal Kubernetes services

Solution

1. Step 1: Understand Ingress controller purpose

   Ingress controllers manage how external users access services inside the Kubernetes cluster.

2. Step 2: Identify correct function

   Nginx and Traefik route incoming traffic to the right service based on rules.

3. Final Answer:

   To route external traffic to internal Kubernetes services -> Option D

4. Quick Check:

   Ingress controller = traffic router [OK]

Hint: Ingress controllers route external traffic inside Kubernetes [OK]

Common Mistakes:

• Confusing ingress controller with node management
• Thinking ingress stores images
• Mixing ingress with monitoring tools

2. Which annotation correctly specifies the use of the Nginx ingress controller in a Kubernetes Ingress resource?

easy

A. kubernetes.io/ingress.class: "nginx"

B. ingress.kubernetes.io/controller: "traefik"

C. kubernetes.io/controller: "nginx"

D. ingress.class: "nginx-controller"

Solution

1. Step 1: Recall correct annotation key for ingress class

   The standard annotation to specify ingress controller is kubernetes.io/ingress.class.

2. Step 2: Match correct value for Nginx

   The value for Nginx ingress controller is "nginx".

3. Final Answer:

   kubernetes.io/ingress.class: "nginx" -> Option A

4. Quick Check:

   Annotation key = kubernetes.io/ingress.class [OK]

Hint: Use kubernetes.io/ingress.class: "nginx" for Nginx [OK]

Common Mistakes:

• Using wrong annotation keys
• Mixing Traefik and Nginx values
• Omitting quotes around values

3. Given this Ingress YAML snippet using Traefik:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
  annotations:
    kubernetes.io/ingress.class: "traefik"
spec:
  rules:
  - host: example.com
    http:
      paths:
      - path: /app
        pathType: Prefix
        backend:
          service:
            name: app-service
            port:
              number: 80

What happens when a user visits http://example.com/app/page?

medium

A. Traffic goes to default backend ignoring /app path

B. Traffic is blocked because pathType is incorrect

C. Traffic is routed to the app-service on port 80

D. Ingress controller returns 404 error

Solution

1. Step 1: Analyze ingress rule for host and path

   The rule matches host example.com and path prefix /app, so /app/page matches.

2. Step 2: Check backend service and port

   Requests matching the path are sent to app-service on port 80.

3. Final Answer:

   Traffic is routed to the app-service on port 80 -> Option C

4. Quick Check:

   Path prefix match routes traffic correctly [OK]

Hint: Path prefix routes all subpaths to backend service [OK]

Common Mistakes:

• Assuming pathType Prefix is invalid
• Ignoring host match requirement
• Thinking default backend handles matched paths

4. You deployed an Nginx ingress controller but your Ingress resource is not routing traffic. Which fix is most likely correct?

medium

A. Add annotation kubernetes.io/ingress.class: "nginx" to the Ingress resource

B. Change service port to 8080 in the Ingress backend

C. Remove all annotations from the Ingress resource

D. Restart the Kubernetes API server

Solution

1. Step 1: Identify cause of routing failure

   Ingress controller routes traffic only to Ingress resources with matching ingress.class annotation.

2. Step 2: Apply correct annotation for Nginx

   Adding kubernetes.io/ingress.class: "nginx" tells Nginx controller to manage this Ingress.

3. Final Answer:

   Add annotation kubernetes.io/ingress.class: "nginx" to the Ingress resource -> Option A

4. Quick Check:

   Ingress class annotation enables controller routing [OK]

Hint: Add ingress.class annotation matching controller [OK]

Common Mistakes:

• Changing service port without checking actual port
• Removing annotations disables routing
• Restarting API server does not fix ingress routing

5. You want to expose two services, webapp and api, on the same domain using Traefik ingress. The webapp should respond on / and api on /api. Which Ingress configuration correctly achieves this?

hard

A. Create two Ingresses with same host but no annotations

B. Use one Ingress with two paths: / to webapp and /api to api service, with annotation kubernetes.io/ingress.class: "traefik"

C. Use one Ingress with only /api path to api service, and no path for webapp

D. Create one Ingress with annotation kubernetes.io/ingress.class: "nginx" for Traefik

Solution

1. Step 1: Understand routing requirements

   Both services share the same domain; webapp on root path /, api on /api path.

2. Step 2: Configure single Ingress with multiple paths and correct annotation

   One Ingress resource with two paths and annotation kubernetes.io/ingress.class: "traefik" directs traffic properly.

3. Final Answer:

   Use one Ingress with two paths: / to webapp and /api to api service, with annotation kubernetes.io/ingress.class: "traefik" -> Option B

4. Quick Check:

   Multiple paths in one Ingress with correct class [OK]

Hint: One Ingress, multiple paths, correct ingress.class annotation [OK]

Common Mistakes:

• Using wrong ingress.class annotation for Traefik
• Creating multiple Ingresses without annotations
• Missing path for root service