Dockerfile linting
Definition
Dockerfile linting is the process of analyzing Dockerfiles to ensure they adhere to best practices and security guidelines. This involves checking for common issues such as unnecessary privileges, inefficient layering, and insecure configurations. Linting tools help automate this process, providing feedback and recommendations to improve the security and efficiency of Docker images.
Secure Settings Example
# Use a minimal base image to reduce attack surface
FROM alpine:3.18
# Set a non-root user for running the application
RUN addgroup -S appgroup && adduser -S appuser -G appgroup
USER appuser
# Copy application files
COPY --chown=appuser:appgroup ./app /app
# Use a specific, non-latest tag for dependencies
RUN apk add --no-cache python3=3.10.11-r0
# Specify a health check to ensure the container is running correctly
HEALTHCHECK --interval=30s --timeout=5s CMD curl -f http://localhost/ || exit 1
Insecure Settings Example
# Use a large, generic base image
FROM ubuntu:latest
# Run as root user, increasing risk of privilege escalation
USER root
# Copy application files without setting ownership
COPY ./app /app
# Install dependencies without specifying versions
RUN apt-get update && apt-get install -y python3
# No health check defined