Deploying a Web Application on Linux using Docker and Kubernetes
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(Technology is always updating,
changing at a very fast pace, depending on when you are reading this in future,
the codes and steps shown here might not be working. Always find a recent
tutorial. There are video links for 4 good Docker and Kubernetes tutorials,
please watch them too and again always find the latest tutorials.)
Containerization and
orchestration have revolutionized the way we deploy and manage web
applications. Docker and Kubernetes are two powerful tools that, when combined,
provide an efficient and scalable way to deploy web applications on Linux
servers. In this comprehensive guide, we will walk you through the step-by-step
process of deploying a web application using Docker and Kubernetes, enabling
you to harness the full potential of these cutting-edge technologies.
Prerequisites
Before we dive into the deployment
process, make sure you have the following prerequisites:
1. A Linux server or virtual
machine with Docker and Kubernetes installed.
2. A web application
containerized using Docker.
3. A basic understanding of
Docker and Kubernetes concepts.
Part 1: Containerizing the Web
Application with Docker
If your web application is not
containerized yet, the first step is to create a Docker image that encapsulates
your application and its dependencies. This allows for consistent and portable
deployment across different environments.
Step 1: Dockerfile
Create a `Dockerfile` in the root
directory of your web application. The `Dockerfile` contains instructions for
building the Docker image.
Here's a basic example of a
`Dockerfile` for a Node.js web application:
```Dockerfile
# Use a base image with Node.js
pre-installed
FROM node:14
# Set the working directory
inside the container
WORKDIR /app
# Copy package.json and
package-lock.json to the container
COPY package*.json ./
# Install application dependencies
RUN npm install
# Copy the rest of the
application files to the container
COPY . .
# Expose the port that the web
application listens on
EXPOSE 3000
# Start the web application
CMD ["npm",
"start"]
```
Step 2: Build the Docker Image
Use the following command to
build the Docker image:
```bash
docker build -t
your-app-name:latest .
```
Replace `your-app-name` with a
meaningful name for your application.
Step 3: Test the Docker Image
You can test the Docker image
locally by running it as a container:
```bash
docker run -d -p 3000:3000
your-app-name:latest
```
Open a web browser and navigate
to `http://localhost:3000` to ensure that your web application is running
correctly inside the Docker container.
Part 2: Deploying with Kubernetes
Now that your web application is
containerized with Docker, let's move on to deploying it with Kubernetes.
Step 1: Set Up Kubernetes
Cluster
If you don't already have a
Kubernetes cluster, you can set up a local development cluster using Minikube
or use a managed Kubernetes service like Google Kubernetes Engine (GKE), Amazon
Elastic Kubernetes Service (EKS), or Microsoft Azure Kubernetes Service (AKS).
Step 2: Define Kubernetes
Deployment
Create a Kubernetes deployment
configuration file, such as `deployment.yaml`, to define how Kubernetes should
run your application:
```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: your-app-deployment
spec:
replicas: 3 # Adjust the number of replicas as needed for your
application
selector:
matchLabels:
app: your-app
template:
metadata:
labels:
app: your-app
spec:
containers:
- name: your-app-container
image: your-app-name:latest
ports:
- containerPort: 3000
```
Step 3: Apply the Deployment
Use `kubectl` to apply the
deployment configuration and create the deployment:
```bash
kubectl apply -f deployment.yaml
```
Step 4: Expose the Deployment
Next, you need to expose your
application to the internet by creating a Kubernetes Service. This allows
external traffic to reach your web application pods.
Create a Service configuration
file, such as `service.yaml`:
```yaml
apiVersion: v1
kind: Service
metadata:
name: your-app-service
spec:
selector:
app: your-app
ports:
- protocol: TCP
port: 80
targetPort: 3000
type: LoadBalancer
```
Apply the Service configuration:
```bash
kubectl apply -f service.yaml
```
Step 5: Verify Deployment
Verify that your application is
running and accessible:
```bash
kubectl get deployments
kubectl get pods
kubectl get services
```
You should see your application's
deployment, pods, and service listed.
Part 3: Scaling and Updating
the Application
One of the major benefits of
using Kubernetes is its ability to scale and update applications easily.
### Scaling the Application
To scale the application, you can
adjust the number of replicas in the deployment configuration:
```bash
kubectl scale deployment
your-app-deployment --replicas=5
```
This command increases the number
of replicas to 5, effectively scaling your application horizontally.
Updating the Application
If you make changes to your web
application's code, rebuild the Docker image with a new tag, and then update
the Kubernetes deployment:
```bash
docker build -t
your-app-name:new-version .
kubectl set image
deployment/your-app-deployment your-app-container=your-app-name:new-version
```
This updates the application to
the new version without downtime.
Conclusion
Deploying a web application on
Linux using Docker and Kubernetes provides a scalable, reliable, and
maintainable solution. With Docker, you can containerize your web application,
ensuring consistency across different environments. Kubernetes takes care of
managing the deployment, scaling, and updating of your application
effortlessly.
By following the steps in this
guide, you've learned how to containerize your web application with Docker,
deploy it on a Kubernetes cluster, and leverage Kubernetes' powerful features
for scaling and updating your application seamlessly. This powerful combination
of Docker and Kubernetes empowers developers and operators to build and manage
robust, cloud-native web applications with ease.
Ref:
1. Docker Crash Course for
Absolute Beginners:
https://www.youtube.com/watch?v=pg19Z8LL06w
2. Docker Tutorial for Beginners
[FULL COURSE in 3 Hours]
https://www.youtube.com/watch?v=3c-iBn73dDE
3. Docker Containers and
Kubernetes Fundamentals – Full Hands-On Course
https://www.youtube.com/watch?v=kTp5xUtcalw
4. Kubernetes Course - Full
Beginners Tutorial (Containerize Your Apps!)
https://www.youtube.com/watch?v=d6WC5n9G_sM
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