SlimToolkit
title: SlimToolkit radar_quadrant: Tools radar_ring: Assess radar_position: inner created: 2026-05-22 last_updated: 2026-05-22 related: ["DockerSecuritySelfHosting", "ContinuousIntegration"]
SlimToolkit (formerly DockerSlim) is a CNCF sandbox tool that minifies Docker container images 10–30x without requiring changes to the Dockerfile or application code. It works by observing what the running container actually accesses at runtime and stripping everything else, then optionally generating Seccomp and AppArmor security profiles from the same observation.
slim build — the core command. Runs the container, observes file system and network access, produces a minified image and optional security profiles:
slim build --target my-app:latestslim xray — analyses image layer contents before and after optimisation; useful for understanding what's inside an image.
slim debug — troubleshoots slimmed containers by temporarily restoring a debug shell, since optimised containers typically have no shell or package manager.
Typical results: 10–30x smaller images. A 200MB Node.js image may slim to 15–20MB; a Python Flask image may slim from 900MB to under 30MB. Results vary by application type and dependencies accessed at runtime.
| Approach | Requires Dockerfile changes | Works on existing images | Security profiles |
|---|---|---|---|
| Multi-stage builds | Yes | No | No |
| Distroless / Alpine base | Yes (new base image) | No | No |
| SlimToolkit | No | Yes | Yes (auto-generated) |
SlimToolkit is complementary to minimal base images — start with Alpine or distroless, then slim further. It is most valuable when rewriting Dockerfiles is impractical (third-party images, large legacy builds).
Add as a post-build step:
docker build -t my-app:fat .
slim build --target my-app:fat --tag my-app:slim
docker push my-app:slimSlimToolkit sits at Tools → Assess inner. Container image size directly affects pull times, storage costs, and attack surface. SlimToolkit requires no code changes and produces both a minified image and Seccomp/AppArmor profiles — two security hardening outputs from one command. CNCF sandbox status indicates community backing. Trial gate: a production image slimmed with verified functionality and the generated security profile reviewed and applied.
