🛠️ Understanding the Dockerfile

Dockerfile

is a script that contains a set of instructions used to build a Docker image. Each instruction adds a layer to the image, helping define the runtime environment for your application.

🔧 Common Dockerfile Instructions

```
FROM
```
: Sets the base image for the container.
```
WORKDIR
```
: Sets the working directory inside the image.
```
COPY
```
/
```
ADD
```
: Copies files from the host into the container.
```
RUN
```
: Executes commands in the image during build (e.g., install dependencies).
```
CMD
```
/
```
ENTRYPOINT
```
: Sets the default command to run in the container.
```
EXPOSE
```
: Documents the port on which the container will listen.
```
ENV
```
: Sets environment variables.
```
ARG
```
: Defines build-time variables.
```
VOLUME
```
: Creates mount points for external volumes.
```
LABEL
```
: Adds metadata to the image.
```
USER
```
: Specifies which user the container runs as.

🧪 Example Dockerfile (Node.js)

Below is a simple Dockerfile to containerize a Node.js application.

# Use an official Node.js runtime as the base image
FROM node:18

# Set the working directory inside the container
WORKDIR /usr/src/app

# Copy dependency definitions
COPY package*.json ./

# Install dependencies
RUN npm install

# Copy the rest of the application
COPY . .

# Expose the app port
EXPOSE 3000

# Run the application
CMD ["npm", "start"]

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