Labs on Nerdsid.com

The Kubernetes Pod That Refused to Die

Wed, 19 Aug 2026 12:00:00 +0000

The last task asks you to delete a pod. kubectl delete pod says success. Then the pod comes back. A kubelet is reading a manifest from disk. Find that file, and you find the answer.

Environment - Kubernetes v1.35.0 on Ubuntu 22.04.5

Tested 2026-08-18 on KodeKloud’s two-node CKA playground: Kubernetes v1.35.0 installed by kubeadm, containerd 1.7.22, flannel CNI. Throughout this post k is an alias for kubectl.

Kubernetes DaemonSets

Mon, 17 Aug 2026 10:00:00 +0000

DaemonSet runs exactly one Pod per matching node, and it schedules onto new nodes automatically as they join the cluster. That’s why CNI plugins, log shippers and node exporters are almost always DaemonSets rather than Deployments.

Five short tasks below: three about reading an existing cluster, two about building a DaemonSet from scratch. Everything assumes the usual alias:

alias k=kubectl

Task 1: How many DaemonSets exist cluster-wide?

The trap is the default namespace scoping — you have to ask for all namespaces explicitly:

Kubernetes Resource Limits

Mon, 17 Aug 2026 09:15:00 +0000

Resource limits look trivial on a slide and then bite you at 3 AM when a container keeps restarting with exit code 137. This lab walks through five short tasks on Pod requests and limits — reading them, diagnosing a crash caused by them, and changing them on a live cluster.

Everything below assumes the usual alias:

alias k=kubectl

Task 1: Identify the CPU requirements on the `rabbit` Pod

A Pod called rabbit is running in the default namespace. The question asks for its CPU requirement — which means the request, not the limit.

Using Shell Variables to Avoid Errors

Wed, 12 Aug 2026 00:00:00 +0000

Task

Create two files (release.txt, owner.txt) under a directory release-packages/northwind-api. The goal is to avoid typos by storing the path once in a variable.

Approach

Store the repeated path in a shell variable (TARGET_DIR), then reference it for both directory creation and file writes.

Solution

file.sh

#!/bin/bash
set -euo pipefail
TARGET_DIR=release-packages/northwind-api
mkdir -p "$TARGET_DIR"
echo 'release=2026.06.09' > "$TARGET_DIR/release.txt"
echo 'owner=platform' > "$TARGET_DIR/owner.txt"

Now run the script using chmod +x file.sh, then ./file.sh.

Verification

Cat file contents

$ cat release-packages/northwind-api/release.txt 
release=2026.06.09
$ cat release-packages/northwind-api/owner.txt
owner=platform

Verification isn’t just a formality. For example, a typo in the path or quoting can fail silently (e.g. create a wrongly named file) instead of throwing an error. So always confirm output rather than trusting the script ran correctly.

Container Cpu Limit Configuration

Wed, 01 Jul 2026 13:30:50 +0000

Introduction

In this lab, you’ll limit the CPU usage of a Docker container that consumes excessive CPU resources.

Scenario

A container named cpu_test is running from the myapp:cpu image and performs CPU-intensive computations. When monitored with docker stats, the container regularly consumes 150–200% CPU, utilizing multiple CPU cores and impacting other services on the host.

Task

Recreate the container with a CPU limit of 500m CPU so that docker stats reports CPU usage consistently below 60% during validation.

Docker Compose Basic

Wed, 01 Jul 2026 11:38:29 +0000

Introduction

In this lab, you’ll first deploy an application by setting up network, multiple containers individually. Then you will clean up resources, and deploy the same application using Docker Compose.

Task 1: Create a Bridge Network

Create a bridge network named clicknet.

docker network create --driver bridge clicknet

Verify

list docker networks

$ docker network ls
NETWORK ID NAME DRIVER SCOPE
5aa54ade2dcc bridge bridge local
fc40bfcbce91 clicknet bridge local
238b23f4e2a9 host host local
59b9cbf97489 none null local

Task 2: Run a Redis Container

Create a background container named redis using the redis:alpine image and attach it to the clicknet network.

Practical Grep: Filtering Errors and Patterns in Log Files

Tue, 30 Jun 2026 11:41:54 +0000

Introduction

This walkthrough covers using grep to search and filter log files for errors, specific requests, and multi-pattern matches.

Tasks

Find all ERROR messages in system.log and count how many there are.
Find all lines containing POST requests in access.log.
Find all lines in application.log that contain both WARNING and query (case-insensitive).
Search for all user authentications (containing User authenticated) across all log files.

Requirements

Use grep for all searches (combining with other commands like wc where needed).
Save each task’s output to its own file: task1_output.txt, task2_output.txt, task3_output.txt, task4_output.txt.
Original log files must not be modified.

Solution

Task 1

grep -c "ERROR" system.log > task1_output.txt

grep -c counts the number of matching lines instead of printing them. Redirecting the output saves the count to task1_output.txt.

Docker Environment Variables and Networking

Tue, 16 Jun 2026 06:50:38 +0000

In this lab, we’ll explore:

Inspecting environment variables in running containers
Passing environment variables at runtime
Deploying MySQL containers
Creating custom Docker networks
Connecting applications and databases across containers

Task 1: Inspect Environment Variables

First, identify the value configured for the APP_COLOR environment variable in a running container.

List the running containers:

$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
cdf886f902d4 kodekloud/simple-webapp "python app.py" 10 minutes ago Up 10 minutes 8080/tcp mystifying_knuth

Inspect the container and look for the Env section:

Custom Resource Definition

Tue, 02 Jun 2026 05:54:03 +0000

Task 1

CRD objects can be either namespaced or cluster-scoped.

Is this statement true or false?

Answer: True

Task 2

What is a custom resource?

Answer: A custom resource is an extension of the Kubernetes API that is not necessarily available in a default Kubernetes installation.

Task 3

We have provided an incomplete Custom Resource Definition (CRD) manifest located at /root/crd.yaml. Complete the file to define a namespaced CRD named internals.datasets.kodekloud.com.

Docker Basic Commands

Mon, 01 Jun 2026 12:33:56 +0000

Task 1

What is the version of the Docker Server Engine running on the host?

Check Docker version

$ docker version

Client:
Version: 25.0.5
API version: 1.44

Server:
Engine:
Version: 25.0.5
API version: 1.44

Answer: 25.0.5

Task 2

How many containers are currently running on this host?

List running containers

$ docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

Answer: 0

Task 3

How many images are available on this host?

Deployments in Kubernetes

Wed, 06 May 2026 15:06:12 +0000

Tasks

Task 1

How many PODs exist on the system?

$ k get po
No resources found in default namespace.

Ans: 0

Task 2

How many ReplicaSets exist on the system?

$ k get rs
No resources found in default namespace.

Task 3

How many Deployments exist on the system?

$ k get deploy
No resources found in default namespace.

Task 4

How many Deployments exist on the system now?

Pods in Kubernetes

Tue, 05 May 2026 16:46:53 +0000

Task

The lab consists of a k8s master node & worker node. You have access to a terminal on the controlplane.

Task 1

How many pods exist on the system?

list pods

$ k get po
No resources found in default namespace.

Ans: 0

Task 2

Create a new pod using the nginx image.

Ans:

$ kubectl run nginx --image=nginx
pod/nginx created

The basic syntax is:

Publishing Ports in Docker

Fri, 01 May 2026 14:37:01 +0000

Task

Solution

Show solution

This is the first paragraph of detailed content. This is the second paragraph of even more detailed content.

You can also include lists
Or other markdown elements

service/networking/network-policy-default-deny-egress.yaml

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
 name: default-deny-ingress
spec:
 podSelector: {}
 policyTypes:
 - Ingress

ls -R /etc/
grep "name" file.txt

name = "God"
greeting = f"Hello {name}"
print(greeting)

Terminal output

Before

Labs on Nerdsid.com

The Kubernetes Pod That Refused to Die

Kubernetes DaemonSets

Task 1: How many DaemonSets exist cluster-wide?

Kubernetes Resource Limits

Task 1: Identify the CPU requirements on the rabbit Pod

Using Shell Variables to Avoid Errors

Task

Approach

Solution

Verification

Container Cpu Limit Configuration

Introduction

Scenario

Task

Docker Compose Basic

Introduction

Task 1: Create a Bridge Network

Verify

Task 2: Run a Redis Container

Practical Grep: Filtering Errors and Patterns in Log Files

Introduction

Tasks

Requirements

Solution

Task 1

Docker Environment Variables and Networking

Task 1: Inspect Environment Variables

Custom Resource Definition

Task 1

Task 2

Task 3

Docker Basic Commands

Task 1

Task 2

Task 3

Deployments in Kubernetes

Tasks

Task 1

Task 2

Task 3

Task 4

Pods in Kubernetes

Task

Task 1

Task 2

Publishing Ports in Docker

Task

Solution

Terminal output

Task 1: Identify the CPU requirements on the `rabbit` Pod