Container Security & Best Practices
Our DevOps consultants build optimized, secure container images and CI/CD pipelines for production workloads.
What Is a Dockerfile
A Dockerfile is a text file containing sequential instructions that Docker uses to build a container image. Each instruction creates a layer in the image, and Docker caches layers to speed up subsequent builds. Dockerfiles define the operating system base, application dependencies, source code, configuration, and startup commands for containerized applications.
Writing efficient, secure Dockerfiles is a core DevOps skill. Poorly constructed Dockerfiles produce bloated images with security vulnerabilities, slow build times, and runtime issues. This tool generates Dockerfiles following current best practices for common application stacks.
Key Dockerfile Instructions
| Instruction | Purpose | Example |
|---|---|---|
| FROM | Set the base image | FROM node:20-alpine |
| WORKDIR | Set the working directory | WORKDIR /app |
| COPY | Copy files from build context | COPY package*.json ./ |
| RUN | Execute commands during build | RUN npm ci --production |
| ENV | Set environment variables | ENV NODE_ENV=production |
| EXPOSE | Document the container port | EXPOSE 3000 |
| USER | Set the runtime user | USER node |
| CMD | Default runtime command | CMD ["node", "server.js"] |
| ENTRYPOINT | Fixed runtime executable | ENTRYPOINT ["python"] |
| HEALTHCHECK | Define health check | HEALTHCHECK CMD curl -f http://localhost/ |
Common Use Cases
- Application containerization: Generate Dockerfiles for Node.js, Python, Go, Java, Ruby, and .NET applications with correct base images and build steps
- Multi-stage builds: Create optimized images that separate build dependencies from runtime, reducing final image size by 50-90%
- CI/CD pipeline images: Build custom images for CI runners with specific tool versions and configurations
- Development environments: Create consistent development containers that eliminate "works on my machine" issues
- Microservice deployment: Generate standardized Dockerfiles for microservice architectures with consistent patterns
Best Practices
- Use multi-stage builds — Separate build and runtime stages. Copy only the compiled output into the final stage, leaving build tools, source code, and dev dependencies behind.
- Use specific base image tags — Pin base images to specific versions (node:20.11-alpine) rather than :latest. This ensures reproducible builds and prevents unexpected breaking changes.
- Run as non-root — Add a USER instruction to run the application as a non-root user. Running containers as root is a significant security risk.
- Order instructions for cache efficiency — Copy dependency files (package.json, requirements.txt) before source code. Dependencies change less frequently, so Docker can cache those layers.
- Use .dockerignore — Exclude node_modules, .git, local configs, and other unnecessary files from the build context to reduce image size and build time.
- Minimize layers — Combine related RUN commands with && to reduce the number of layers. Each layer adds overhead to the image.
Frequently Asked Questions
Common questions about the Dockerfile Generator
Multi-stage builds use multiple FROM statements to separate build and runtime stages. Build dependencies stay in build stages, while only runtime artifacts go into the final image. This dramatically reduces image size and attack surface.