DEV Community: Dechen Tshering

🚀 Understanding Kubernetes Services: ClusterIP, NodePort, LoadBalancer + Manual Scheduling

Dechen Tshering — Sun, 04 May 2025 16:04:00 +0000

Hey everyone! 👋
As part of my DevOps learning in public, I’ve been diving deep into Kubernetes and exploring how Services work—particularly how to expose applications inside and outside the cluster using different service types.

In this blog, I’ll walk you through my experiments using ClusterIP, NodePort, and LoadBalancer, along with a quick intro to manual pod scheduling on specific nodes.

Let’s go! 🚀

⚙️ Step 1: Create a ReplicaSet

First, I created a simple ReplicaSet using the following YAML:

# myapp.yml
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: webapp
spec:
  replicas: 5
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: mycontainer
        image: nginx

Apply it:

kubectl apply -f myapp.yml

Demo 1: ClusterIP

ClusterIP is the default service type and is only accessible within the cluster.

# cip.yml
apiVersion: v1
kind: Service
metadata:
  name: mysvc
spec:
  type: ClusterIP
  ports:
  - targetPort: 80     # container port
    port: 5000         # service port
  selector:
    app: web

Or expose it using the CLI:

kubectl expose rs webapp --target-port=80 --port=5000 --name=mysvc

Access It:

Get the service IP:

kubectl get svc

Get any node name:

kubectl get nodes -o wide

Start a debug pod on that node:

kubectl debug node/<NODE_NAME> -it --image=nginx

Inside the pod:

apt-get update -y && apt-get install curl -y
curl <SERVICE_IP>:5000

Demo 2: NodePort

NodePort allows you to access your service externally on a static port on any worker node.

# nodeport.yml
apiVersion: v1
kind: Service
metadata:
  name: web-node-port
spec:
  type: NodePort
  ports:
  - targetPort: 80
    port: 80
    nodePort: 30002
  selector:
    app: web

Or use:

kubectl expose rs webapp --target-port=80 --port=80 --type=NodePort

Access It:

Get the node IP:

kubectl get nodes -o wide

Curl from a debug pod:

curl <NODE_IP>:30002

Demo 3: LoadBalancer

LoadBalancer is commonly used in cloud environments to expose services publicly using an external IP.

# lb.yml
apiVersion: v1
kind: Service
metadata:
  name: mysvc
spec:
  type: LoadBalancer
  ports:
  - targetPort: 80
    port: 80
  selector:
    app: web

Or via CLI:

kubectl expose rs webapp --target-port=80 --port=80 --type=LoadBalancer

Access It:

kubectl get svc
# Use the external IP shown to access your app in the browser

Note: This works on cloud providers like GCP, AWS, or Azure. On Minikube or bare metal, you may need MetalLB or another load balancer.

Bonus: Manual Scheduling

I also tried manually scheduling a pod to a specific node. This can be helpful when testing specific node configurations or behavior.

# pod.yml
apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
spec:
  containers:
  - name: nginx-container
    image: nginx
  nodeName: <NODE_NAME>

Just replace with a real node name from:

kubectl get nodes

Apply it:

kubectl apply -f pod.yml

Key Learnings

ClusterIP: Great for internal communication between services.
NodePort: Exposes apps on every node's IP at a static port.
LoadBalancer: Best for public access when running on cloud providers.
Manual scheduling gives control, but use it with caution in production. _

If you're also learning Kubernetes, let’s connect and grow together! 🌱
Drop a comment if this was helpful or if you’ve got tips of your own 🙌

Learning Kubernetes: ReplicationController vs ReplicaSet

Dechen Tshering — Sun, 27 Apr 2025 19:14:17 +0000

As I dive deeper into Kubernetes, I’ve been exploring the concepts of ReplicationControllers and ReplicaSets—two core constructs used to ensure high availability and scalability of pods in a Kubernetes cluster.

In this post, I’ll share what I learned, along with sample YAML definitions and key commands. Hopefully, it helps anyone else navigating this space too!

What is a ReplicationController?

A ReplicationController (RC) ensures that a specified number of pod replicas are running at any given time. While it’s considered a bit old-school now (ReplicaSet and Deployments have largely replaced it), it’s still a fundamental concept worth understanding.

Here’s a sample YAML to create a ReplicationController:

apiVersion: v1
kind: ReplicationController
metadata: 
  name: myrc
spec: 
  replicas: 5
  template:
    metadata:
      labels: 
        app: web
    spec:
      containers:
      - name: c1
        image: nginx

Basic ReplicationController Commands

List all RCs:

kubectl get rc or kubectl get replicationcontroller

Delete an RC:

kubectl delete rc <rc-name>

Scale the RC:

kubectl scale --replicas=<number> rc/<rc-name>

What is ReplicaSet?

A ReplicaSet (RS) is the next-gen version of RC, introduced with better support for label selectors, including set-based ones. It ensures that a specified number of pod replicas are maintained and is mostly used under the hood by Deployments.

Example 1: Equality-Based Selector:

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: mywebapp
spec:
  replicas: 5
  selector:
    matchLabels: 
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: c1
        image: nginx

Example 2: Set-Based Selector:

apiVersion: apps/v1
kind: ReplicaSet
metadata: 
  name: webdata
spec:
  replicas: 4
  selector:
    matchExpressions:
    - key: app
      operator: In
      values:
        - nginx
        - web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: c1
        image: nginx

Basic Replica Set Commands:

List all ReplicaSets

kubectl get rs

This shows all the ReplicaSets in your current namespace.

Describe a ReplicaSet

kubectl describe rs <replicaset-name>

Provides detailed information including events, pod template, and selector.

Delete a ReplicaSet

kubectl delete rs <replicaset-name>

Deletes the ReplicaSet

Scale a ReplicaSet

kubectl scale rs/<replicaset-name> --replicas=3

Adjusts the number of desired pod replicas.

Edit a ReplicaSet

kubectl edit rs <replicaset-name>

Opens the ReplicaSet manifest in your default editor so you can make changes on the fly.

Apply from a YAML file

kubectl apply -f webrs.yml

Creates or updates a ReplicaSet from a manifest file.

View pods managed by a ReplicaSet

kubectl get pods -l app=web

Use label selectors to filter pods created by the ReplicaSet.

Key difference between ReplicationController and ReplicaSet:

Feature	ReplicationController (RC)	ReplicaSet (RS)
API Version	`v1`	`apps/v1`
Label Selector Support	Equality-based only	Equality & set-based
Usage	Legacy / older systems	Modern replacement for RC
Used by Deployment	No	Yes
Flexibility	Less flexible	More flexible
Community Support	Deprecated	Actively supported

After getting comfortable with Replication Controllers and Replica Sets, I’ve realized they’re just the beginning. Now, I’m excited to dive into Deployments—the real game-changer for managing apps in Kubernetes!

🚀 Kubernetes Pod Commands & YAML Guide – Quick Reference for Devs & DevOps

Dechen Tshering — Sun, 27 Apr 2025 18:19:14 +0000

Whether you're new to Kubernetes or want a clean reference sheet, here’s a quick guide to working with Kubernetes Pods using the CLI and YAML definitions.
This post includes essential commands, how to access pods and containers and how to create pods using YAML.

Essential kubectl Commands for Pods.

Create a pod

kubectl run --image=

List all pods

kubectl get pods

List pods with extended details (IP address, node, etc.)

kubectl get pods -o wide

Access a running pod shell

kubectl exec -it -- bash

Access a specific container inside a multi-container pod

kubectl exec -it -c -- bash

Describe pod details

kubectl describe pod

Get detailed node information (container runtime, etc.)

kubectl get nodes -o wide

Delete a pod

kubectl delete pod

** Create a Pod Using YAML**

vim pod.yaml

apiVersion: v1
kind: Pod
metadata:
name: abc
spec:
containers:

name: c1 image: nginx
name: c2 image: redis

Commands:

Create resources from YAML

kubectl create -f pod.yaml

Delete resources from YAML

kubectl delete -f pod.yaml

Access Shell Inside Pod/Container

Access the shell of a pod

kubectl exec -it -- sh

Access a specific container in a pod

kubectl exec -it -c -- sh

If this helped you or you'd like to keep a quick reference around, feel free to bookmark or share this post! 🚀
Let’s keep growing together in the world of Cloud Native, Kubernetes, and DevOps.

My Kubernetes Learning Notes: Image Pull Policy, Labels & Selectors

Dechen Tshering — Sun, 20 Apr 2025 15:18:41 +0000

Hey folks!
As I continue learning Kubernetes, I’ve been digging into some foundational concepts that I think are super important to understand early on — Image Pull Policies, Labels, and Selectors.
Thought I'd share what I’ve learned so far in case it helps anyone else on the same path!

Image Pull Policy in Kubernetes

There are three options:

Always

This will always pull the image from the container registry (like Docker Hub), no matter what. It’s great if you're constantly updating the image and want to make sure the latest version is always used.
IfNotPresent

This will only pull the image if it’s not already available locally on the node. It seems to be the default for tagged images, and it is super useful when you’re trying to avoid unnecessary pulls.
Never

This one won’t pull the image at all. Kubernetes just uses whatever is already there on the node. It’s probably best for air-gapped or strictly controlled environments.

Example of how I used it in a YAML file:


apiVersion: v1
kind: Pod
metadata:
  name: abc
spec:
  containers:
  - name: nginx-pod
    image: nginx
    imagePullPolicy: IfNotPresent

Labels in Kubernetes

Labels are basically key-value pairs that we can attach to pods (or other Kubernetes objects). They’re really helpful for organizing, filtering, and managing resources.


apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    department: hr
spec:
  containers:
  - name: nginx-container
    image: nginx

Some commands I learned:

kubectl get pods --show-labels       # Show labels for all pods
kubectl label pod <pod-name> <key>=<value>  # Add a new label
kubectl label pod <pod-name> <key>-         # Remove a label
kubectl label --overwrite pod <pod-name> <key>=<value> # Overwrite an existing label

Label Selectors — Equality & Set Based

Selectors let you filter pods based on their labels, which is super handy when you have a lot of resources.

Equality-Based Selectors

These use = and != to match specific key/value pairs.


kubectl get pods --selector department=it   # Only pods with department=it
kubectl get pods --selector department!=it  # All pods except department=it
kubectl get pods -l department=hr           # Another way to filter by label

Set-Based Selectors

These are used when you want to filter by multiple values.



kubectl get pods --selector 'department in (hr,prod)'   # Pods with department=hr or department=prod

These might seem like small details at first, but I'm starting to realize how powerful they are when managing pods and organizing deployments at scale.

Still lots to learn, but this felt like a good checkpoint to share what I’ve picked up

If you're also learning Kubernetes, I would love to hear what helped you wrap your head around these topics! Drop tips or corrections if I missed anything!

If you're also learning Kubernetes, I would love to hear what helped you wrap your head around these topics! Drop tips or corrections if I missed anything!
Feel free to connect:
Hashnode - https://hashnode.com/@dechen-tshering-3577
LinkedIn - https://rb.gy/7w546x

I’ll be posting more as I go!

🚀 Kubernetes Pod Commands & YAML Guide – Quick Reference for Devs & DevOps

Dechen Tshering — Sun, 13 Apr 2025 18:20:16 +0000

Essential kubectl Commands for Pods.

Create a pod
kubectl run <pod-name> --image=<image-name>
List all pods
kubectl get pods
List pods with extended details (IP address, node, etc.)
kubectl get pods -o wide
Access a running pod shell
kubectl exec -it <pod-name> -- bash
Access a specific container inside a multi-container pod
kubectl exec -it <pod-name> -c <container-name> -- bash
Describe pod details
kubectl describe pod <pod-name>
Get detailed node information (container runtime, etc.)
kubectl get nodes -o wide
Delete a pod
kubectl delete pod <pod-name>

Create a Pod Using YAML

vim pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: abc
spec:
  containers:
  - name: c1
    image: nginx

Commands:

Create resources from YAML
kubectl create -f pod.yaml
Delete resources from YAML
kubectl delete -f pod.yaml

Access Shell Inside Pod/Container

Access the shell of a pod
kubectl exec -it <pod-name> -- sh
Access a specific container in a pod
kubectl exec -it <pod-name> -c <container-name> -- sh

If this helped you or you'd like to keep a quick reference around, feel free to bookmark or share this post! 🚀
Let’s keep growing together in the world of Cloud Native, Kubernetes, and DevOps.

🚀 My DevOps Learning Journey – Key Linux Commands 🚀

Dechen Tshering — Sun, 06 Apr 2025 18:57:55 +0000

As I continue my DevOps journey, I’ve been diving into Linux system administration, which is essential for managing infrastructure, automating tasks, and streamlining processes. Here’s a snapshot of some key Linux commands I’ve been mastering that are crucial for any DevOps role:

🔹 File Management

echo: Print text to the screen
ls: List files and folders
cd <dir_name>: Change directory
mkdir <new_directory>: Create a new directory
rm -r <dir>: Remove a directory and its contents
cp -r <source> <destination>: Copy a directory and its contents
mv <source> <destination>: Rename or move files

🔹 User Management
whoami: Show the current user
id: Get user and group info
su : Switch user
sudo : Execute a command with root privileges

🔹 Download Files
curl -O: Download files using curl
wget -O : Download files using wget

🔹 OS Version Check
cat /etc/release: Check the OS version

🔹 Package Management (RPM/YUM)
rpm -i : Install a package
yum install : Install a package using YUM
yum remove : Uninstall a package

🔹 Service Management
systemctl start : Start a service
systemctl stop : Stop a service
systemctl enable : Enable a service at startup
systemctl status : Check service status

These are just a few of the core Linux commands I’ve been mastering to effectively manage systems in a DevOps environment. I’m excited to continue this journey, explore more tools, and learn new technologies along the way!

Special thanks to @savinderpuri for sharing valuable insights and inspiring me throughout this process! 🙏

🚀 Kicking Off My DevOps BootCamp – First Stop: Linux Basics! 🐧

Dechen Tshering — Sun, 06 Apr 2025 18:52:19 +0000

Last week marked the start of my DevOps BootCamp, and I’m super excited to dive into the essential skills needed to thrive in this fast-paced field.

First up: Linux Basics! Since Linux is the backbone of DevOps, I’m focusing on sharpening my command-line skills, mastering file systems, permissions, scripting, and much more. Whether it’s automating tasks or managing servers, a solid foundation in Linux is crucial for any DevOps professional.

I can’t wait to share my progress and key insights along the way. If you’ve been through a similar journey or have any tips to share, I’d love to hear from you in the comments!

DEV Community: Dechen Tshering

🚀 Understanding Kubernetes Services: ClusterIP, NodePort, LoadBalancer + Manual Scheduling

⚙️ Step 1: Create a ReplicaSet

Apply it:

Demo 1: ClusterIP

Or expose it using the CLI:

Access It:

Demo 2: NodePort

Or use:

Access It:

Demo 3: LoadBalancer

Or via CLI:

Access It:

Bonus: Manual Scheduling

Just replace with a real node name from:

Apply it:

Key Learnings

Learning Kubernetes: ReplicationController vs ReplicaSet

What is a ReplicationController?

Here’s a sample YAML to create a ReplicationController:

Basic ReplicationController Commands

List all RCs:

Delete an RC:

Scale the RC:

What is ReplicaSet?

Example 1: Equality-Based Selector:

Example 2: Set-Based Selector:

Basic Replica Set Commands:

List all ReplicaSets

Describe a ReplicaSet

Delete a ReplicaSet

Scale a ReplicaSet

Edit a ReplicaSet

Apply from a YAML file

View pods managed by a ReplicaSet

Key difference between ReplicationController and ReplicaSet:

🚀 Kubernetes Pod Commands & YAML Guide – Quick Reference for Devs & DevOps

Create a pod

List all pods

List pods with extended details (IP address, node, etc.)

Access a running pod shell

Access a specific container inside a multi-container pod

Describe pod details

Get detailed node information (container runtime, etc.)

Delete a pod

vim pod.yaml

Create resources from YAML

Delete resources from YAML

Access the shell of a pod

Access a specific container in a pod

My Kubernetes Learning Notes: Image Pull Policy, Labels & Selectors

Image Pull Policy in Kubernetes

Always

IfNotPresent

Never

Example of how I used it in a YAML file:

Labels in Kubernetes

Some commands I learned:

Label Selectors — Equality & Set Based

Equality-Based Selectors

Set-Based Selectors

🚀 Kubernetes Pod Commands & YAML Guide – Quick Reference for Devs & DevOps

Essential kubectl Commands for Pods.

Create a Pod Using YAML

Commands:

Access Shell Inside Pod/Container

🚀 My DevOps Learning Journey – Key Linux Commands 🚀

🚀 Kicking Off My DevOps BootCamp – First Stop: Linux Basics! 🐧