Docker Build Process: Dockerfile to Image to Container

# Layer 1: Base image
FROM node:18-alpine

# Layer 2: Set working directory
WORKDIR /app

# Layer 3: Copy package files
COPY package*.json ./

# Layer 4: Install dependencies
RUN npm install --production

# Layer 5: Copy application code
COPY . .

# Layer 6: Expose port (metadata only)
EXPOSE 3000

# Layer 7: Set environment variable
ENV NODE_ENV=production

# Layer 8: Define startup command (metadata only)
CMD ["node", "app.js"]

# ========== Build Stage ==========
FROM golang:1.21-alpine AS builder

WORKDIR /build

# Copy go mod files
COPY go.mod go.sum ./
RUN go mod download

# Copy source code
COPY . .

# Build the application
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o main .

# ========== Runtime Stage ==========
FROM alpine:latest

# Install ca-certificates for HTTPS
RUN apk --no-cache add ca-certificates

WORKDIR /app

# Copy only the binary from build stage
COPY --from=builder /build/main .

# Create non-root user
RUN addgroup -g 1000 appuser && \
    adduser -D -u 1000 -G appuser appuser && \
    chown -R appuser:appuser /app

USER appuser

EXPOSE 8080

CMD ["./main"]

FROM node:18-alpine
WORKDIR /app
# Copies everything, invalidates cache on any change
COPY . .
RUN npm install
CMD ["node", "app.js"]

FROM node:18-alpine
WORKDIR /app

# Copy dependency files first (changes rarely)
COPY package*.json ./
RUN npm install --production

# Copy source code last (changes frequently)
COPY . .

CMD ["node", "app.js"]

# Build an image
docker build -t myapp:v1.0 .
docker build -t myapp:v1.0 -f Dockerfile.prod .

# List images
docker images
docker image ls

# Run a container
docker run -d -p 8080:3000 --name myapp-container myapp:v1.0
docker run -it --rm myapp:v1.0 /bin/sh  # Interactive shell

# List containers
docker ps        # Running containers
docker ps -a     # All containers

# View logs
docker logs myapp-container
docker logs -f myapp-container  # Follow logs

# Execute command in running container
docker exec -it myapp-container /bin/sh

# Stop and remove
docker stop myapp-container
docker rm myapp-container

# Remove image
docker rmi myapp:v1.0

# Clean up
docker system prune -a  # Remove unused images, containers, networks
docker volume prune     # Remove unused volumes

# ❌ Bad: Version can change
FROM node:latest

# ✅ Good: Specific version
FROM node:18.17.0-alpine3.18

# Create and use non-root user
RUN addgroup -g 1001 -S nodejs && \
    adduser -S nodejs -u 1001

USER nodejs

node_modules
npm-debug.log
.git
.env
*.md
.vscode

# ❌ Bad: Multiple RUN commands
RUN apk add --no-cache git
RUN apk add --no-cache curl
RUN apk add --no-cache vim

# ✅ Good: Single RUN command
RUN apk add --no-cache \
    git \
    curl \
    vim