# Slim — Optimize Docker Containers with Automatic Minification

> Slim (formerly DockerSlim) automatically analyzes and optimizes container images, shrinking them up to 30x by removing unnecessary files, packages, and layers.

## Install

Save in your project root:

# Slim — Optimize Docker Containers with Automatic Minification

## Quick Use
```bash
# Install Slim
curl -sL https://raw.githubusercontent.com/slimtoolkit/slim/master/scripts/install-slim.sh | sudo bash

# Minify a Docker image
slim build my-app:latest

# Inspect an image without changing it
slim xray my-app:latest
```

## Introduction
Slim (formerly DockerSlim) is an open-source tool that automatically shrinks container images by analyzing what your application actually needs at runtime. Instead of manually crafting multi-stage builds or stripping packages by hand, Slim instruments your container, observes which files and libraries are accessed, and produces a minimal image with only those components. The result is dramatically smaller, faster, and more secure images.

## What Slim Does
- Analyzes container images using static analysis and dynamic probing to identify used files
- Produces minified images that are 5-30x smaller than the originals
- Removes unused packages, shell utilities, and OS files that expand attack surface
- Generates AppArmor and Seccomp security profiles automatically
- Supports Dockerfile-less optimization of any existing image from any registry

## Architecture Overview
Slim works by launching your container in an instrumented sandbox that monitors file system access, network calls, and process execution using kernel-level sensors (ptrace, seccomp-bpf, fanotify). After the probing phase completes, Slim builds a dependency graph of every file and library your application touched. It then constructs a new minimal image containing only those artifacts, preserving the original entrypoint and environment configuration.

## Self-Hosting & Configuration
- Install the slim binary on your CI runner or developer machine via the install script
- Run slim build <image> to produce an optimized variant tagged with .slim suffix
- Use --http-probe=true to automatically probe HTTP endpoints during analysis
- Add --include-path to manually include extra files or directories the probe might miss
- Integrate into CI/CD pipelines by running slim after docker build for automatic optimization

## Key Features
- Zero-config optimization that works on most Docker images without modification
- Built-in HTTP probing that exercises web applications during the analysis phase
- Automatic security profile generation (AppArmor and Seccomp) for hardened containers
- Image xray command provides a detailed breakdown of layers, files, and wasted space
- Works with any container runtime and registry including Docker Hub, ECR, GCR, and GHCR

## Comparison with Similar Tools
- **Multi-stage Docker builds** — require manual effort to select and copy only needed artifacts
- **Distroless images (Google)** — provide minimal base images but require rebuilding your app on top
- **Alpine Linux** — smaller base but still includes unused packages and needs manual pruning
- **Dive** — excellent for inspecting image layers but does not actually optimize or shrink them
- **crane** — manipulates image layers efficiently but has no runtime analysis or auto-minification

## FAQ
**Q: Will Slim break my application by removing needed files?**
A: Slim uses runtime probing to detect dependencies. For most apps the defaults work. If a file is missed, use --include-path to add it and rebuild.

**Q: Does Slim work with non-HTTP applications?**
A: Yes. You can use --exec to run custom commands during the probing phase, or provide a probe script for databases, CLIs, or background workers.

**Q: How does Slim compare to just using scratch or distroless base images?**
A: Scratch and distroless require you to manually build a static binary. Slim works on any existing image including those based on Ubuntu or Debian.

**Q: Can I use Slim in CI/CD?**
A: Absolutely. Run slim build as a post-build step in GitHub Actions, GitLab CI, or Jenkins to automatically optimize every image before pushing to a registry.

## Sources
- https://github.com/slimtoolkit/slim
- https://slimtoolkit.org/docs

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Source: https://tokrepo.com/en/workflows/bebccaab-3986-11f1-9bc6-00163e2b0d79
Author: AI Open Source