Are Dockerfiles holding us back?

Containers revolutionized software deployment by making it easier to test, deploy, and scale applications consistently. However, as containers have become central to modern workflows, their foundational tool—Dockerfiles—has shown its limitations. Could we do better?

The Promise of Containers

Containers have become the gold standard for deploying software, offering:

  • Consistent environments across development, staging, and production
  • Minimal performance overhead compared to VMs
  • Seamless integration with modern orchestration tools like Kubernetes
  • Improved resource utilization and scaling capabilities
  • Faster deployment cycles and easier rollbacks

However, the tools for creating and managing containers, particularly Dockerfiles, have not kept pace with these advancements.

What Did Containers Replace?

Before containers, infrastructure management often relied on:

  1. Brittle Bash Scripts: Early deployments were plagued by hard-to-maintain scripts. Errors like foo = bar (instead of foo=bar) or unhandled edge cases could wreak havoc.
  2. Configuration Management Tools: Tools like Ansible emerged, providing:
    • Abstraction over OS-level differences
    • Reusable playbooks and event-driven automation
    • Integration with CI/CD pipelines
    • Idempotent operations
    • Detailed logging and error handling

Ansible and similar tools allowed operations teams to confidently manage fleets of servers. Changes could be deployed consistently, and rollback mechanisms were built in.

Enter Docker and the Rise of Dockerfiles

Docker promised a middle ground: developers gained autonomy with containers, while operations retained oversight of host systems. However, Dockerfiles introduced new challenges:

Common Dockerfile Pitfalls

  1. Using latest Tags:

    # Bad practice
FROM ubuntu:latest

# Better practice - using specific version
FROM ubuntu:22.04

# Best practice - using digest
FROM ubuntu@sha256:cf25d3b6e8e2d2826891f27043c3c4c02e0a2e0b9f3f2be4f47fda3d7b3c8b9a

  2. Inefficient Layer Caching:

    # Bad practice - breaking cache unnecessarily
COPY . /app/
RUN pip install -r requirements.txt

# Better practice - leveraging cache
COPY requirements.txt /app/
RUN pip install -r requirements.txt
COPY . /app/

  3. Security Issues:

    # Bad practice - running as root
CMD ["python", "app.py"]

# Better practice - using non-root user
RUN useradd -r -s /bin/false appuser
USER appuser
CMD ["python", "app.py"]

  4. Multi-stage Builds:

    # Better practice - using multi-stage builds
FROM node:16 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

FROM nginx:alpine
COPY --from=builder /app/dist /usr/share/nginx/html

  5. Dependency Management:

    # Bad practice - no version pinning
RUN apt-get update && apt-get install python3 nginx

# Better practice - version pinning
RUN apt-get update && apt-get install python3=3.9.7-1ubuntu0.2 nginx=1.18.0-0ubuntu1.2

Where Do Dockerfiles Fall Short?

Dockerfiles reintroduced many of the brittleness and risks that modern tools like Ansible had mitigated:

  • Lack of versioning for OS-level changes
  • Poor support for testing and validation
  • Limited safeguards against common mistakes
  • No built-in security scanning
  • Difficult dependency management
  • Limited support for complex build workflows

While tools like Hadolint (a Dockerfile linter) help, they don’t address deeper structural issues.

Modern Alternatives to Dockerfiles

1. Cloud Native Buildpacks

Cloud Native Buildpacks provide a higher-level abstraction:

pack build myapp --builder paketobuildpacks/builder:base

Benefits:

  • Automated dependency management
  • Built-in security patches
  • Standardized build process
  • Language-specific optimizations

2. Dockerfiles + Ansible

Use Ansible to define the container environment:

FROM debian:bullseye-slim
COPY ansible /ansible
RUN apt-get update && apt-get install -y python3 ansible && \
    ansible-playbook -c local /ansible/playbook.yml && \
    apt-get remove -y ansible && apt-get autoremove -y

3. BuildKit

BuildKit enhances Dockerfile builds:

# syntax=docker/dockerfile:1.4
FROM base
RUN --mount=type=cache,target=/var/cache/apt \
    apt-get update && apt-get install -y python3
COPY --chmod=755 <<EOF /usr/local/bin/script.sh
#!/bin/sh
echo "Hello, BuildKit!"
EOF

4. Kaniko

Kaniko enables secure builds in Kubernetes:

apiVersion: v1
kind: Pod
metadata:
  name: kaniko
spec:
  containers:
  - name: kaniko
    image: gcr.io/kaniko-project/executor:latest
    args:
    - "--dockerfile=Dockerfile"
    - "--context=git://github.com/my-org/my-project.git"
    - "--destination=gcr.io/my-project/image"

5. Buildah

Buildah provides script-based container builds:

#!/bin/bash
container=$(buildah from debian:bullseye-slim)
buildah run $container apt-get update
buildah run $container apt-get install -y nginx
buildah commit $container my-nginx-image

The Future of Container Building

  1. GitOps Integration:

    • Version-controlled build definitions
    • Automated testing and validation
    • Integrated security scanning

  2. AI-Assisted Building:

    • Automated dependency updates
    • Security vulnerability detection
    • Build optimization suggestions

  3. Cross-Platform Solutions:

    • Better support for multi-architecture builds
    • Improved handling of platform-specific dependencies
    • Seamless integration with various container runtimes

What We Need

  • Declarative APIs: A Terraform-like interface for containers
  • Built-in Security: Automated vulnerability scanning and fixes
  • Smart Caching: Intelligent layer management and build optimization
  • Cross-Platform Support: Better handling of architecture-specific builds
  • Integration with Modern Tools: Native support for GitOps and CI/CD

Conclusion

While Dockerfiles served as a crucial stepping stone in the container revolution, modern applications demand more sophisticated build tools. The future lies in declarative, secure, and intelligent build systems that can handle the complexity of modern containerized applications. Whether through Cloud Native Buildpacks, BuildKit, or emerging technologies, the evolution beyond basic Dockerfiles is not just beneficial—it’s necessary for building robust, secure, and maintainable containerized systems.

Consider exploring alternatives like Cloud Native Buildpacks or BuildKit for your next project, especially if you’re dealing with complex build requirements or need enhanced security features. The container ecosystem is rapidly evolving, and staying current with these tools can significantly improve your development workflow and application security.