Slim — Optimize Docker Containers with Automatic Minification

What it is

Slim (formerly DockerSlim) automatically analyzes and optimizes Docker container images. It instruments your container, observes which files and libraries are actually used at runtime, then builds a minified image containing only those files. The result is an image that is up to 30x smaller with a reduced attack surface.

The tool targets DevOps engineers, security teams, and developers who want smaller, faster, and more secure container images without manually writing multi-stage Dockerfiles.

How it saves time or tokens

Manually optimizing Docker images requires identifying unused packages, writing multi-stage builds, and testing that nothing breaks. Slim automates this entire process: run one command and get an optimized image. No Dockerfile changes needed. The smaller images also reduce registry storage costs and container pull times.

How to use

1. Install Slim: brew install slim or download from GitHub releases.
2. Run Slim against your image: slim build my-app:latest.
3. Use the optimized image: my-app.slim:latest.

Example

# Install Slim
brew install slim

# Optimize a Node.js application image
slim build node-api:latest

# Compare sizes
docker images | grep node-api
# node-api        latest   890MB
# node-api.slim   latest    35MB

# Run the optimized image
docker run -p 3000:3000 node-api.slim:latest

# Advanced: keep specific paths and expose HTTP probes
slim build my-app:latest \
  --include-path /app/config \
  --http-probe-cmd /health

Related on TokRepo

• AI Tools for DevOps -- container and infrastructure optimization tools
• MCP Docker Integration -- Docker management for AI agents

Common pitfalls

• Slim removes files not accessed during its probe phase. If your app has code paths not triggered during probing (e.g., error handlers, cron jobs), those files may be removed. Use --include-path to keep them.
• The probe phase runs your container. Ensure the container can start and respond to health checks in the Slim environment.
• Slim works best with server applications that have clear startup and request handling. Batch jobs or CLI tools may need custom probe commands.