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Distroless images exist to reduce attack surface: they contain the application binary and its runtime dependencies, and nothing else. No shell, no package manager, no curl, no strace. When a distroless container crashes or misbehaves, the standard debugging reflex—docker exec -it <container> /bin/sh—fails because there is no shell to execute . The ephemeral container pattern…

Docker images do not store the original Dockerfile. The image is a stack of layers, and each layer records the instruction that created it, but the full build context—the files that were copied, the arguments passed to docker build—is not preserved in a form that can be reconstructed exactly . Reverse engineering a Dockerfile is…

The CIS Docker Benchmark is a vendor-neutral hardening standard published by the Center for Internet Security, currently at version 1.6.0, with over 100 recommendations organized into seven sections covering the host, daemon, configuration files, images, runtime, operations, and Swarm . Auditors for SOC 2 Type II, PCI DSS 4.0, and FedRAMP accept CIS Docker scores…

High-throughput Docker workloads fail at the host layer before they reach the application layer. The default Linux kernel is configured for balanced desktop and general-purpose server use, not for tens of thousands of concurrent connections. The three parameters that most often become the bottleneck are the file descriptor limit, the ephemeral port range, and the…

The OCI specification defines two independent standards that are often confused: the Runtime Specification describes how to configure and execute a container (the config.json and the lifecycle), and the Image Specification describes how to package a filesystem and its metadata. Building a custom runtime means implementing the former; building a custom image means producing the…

Zero-downtime deployment is not a single technique but a family of patterns that share one requirement: the old version must keep serving traffic until the new version is proven ready. The two patterns that matter most in Docker environments are rolling updates, which replace replicas incrementally, and blue-green, which runs two complete environments and switches…

This chapter traces a single TCP SYN packet from the moment it arrives on the host’s physical network interface to the moment it is delivered to the application listening inside a container. The path is not a straight line. It crosses the host’s network stack, passes through the Netfilter framework where Docker’s NAT rules rewrite…

A quick-reference for Docker commands, concepts, and internals. Organized for lookup, not for reading. Container Lifecycle Command Purpose docker run <image> Create + start container docker run -d <image> Detached (background) docker run -it <image> sh Interactive with TTY docker run –rm <image> Auto-remove on exit docker run –name foo <image> Named container docker start…