Tutorials covering the tools that developers use every day — version control, editors, build systems, package managers, containers, and the command-line utilities that make work faster. Each chapter is standalone, built around real examples and verified commands.
A CI pipeline for Docker images is not a single build step. It is a sequence of decisions: build the image without pushing, run the container to verify it starts, check a health endpoint, then rebuild with the same cache and push the tested artifact. GitHub Actions provides the primitives for this sequence through Docker’s…
The difference between a Docker CI pipeline that finishes in thirty seconds and one that takes four minutes is almost never the code. It is whether the layer cache survived from the previous run. GitHub-hosted runners are ephemeral: every job starts with an empty filesystem, and BuildKit’s local cache—the default mechanism that makes local builds…
The choice between DinD and DooD is a choice about where the Docker daemon lives and who controls it. Docker-in-Docker runs a nested daemon inside the CI job container, giving each job its own isolated Docker environment with its own image cache, network, and storage. Docker-outside-of-Docker mounts the host’s Docker socket into the job container,…
GitOps is a deployment model in which the desired state of the infrastructure is stored in a Git repository, and a controller continuously reconciles the running state with the committed state. The model has two implementations that are often confused: pull-based reconciliation, where an in-cluster agent watches Git and applies changes, and image-update automation, where…
Traefik is a reverse proxy that discovers Docker containers through the Docker socket and routes traffic to them based on labels attached to the container itself. The routing configuration is not a separate file that must be edited when a service is added; it is a set of traefik.http.routers.* and traefik.http.services.* labels on the container,…
Docker’s persistence model creates a specific backup problem: named volumes and bind mounts hold the data that matters, but the container’s writable layer is disposable, and the image is reproducible from a registry. A backup strategy that copies the entire /var/lib/docker directory is fragile and often inconsistent; a strategy that stops the stack and tars…
A packet that leaves a container and reaches the internet passes through at least four distinct processing stages, and each stage is implemented by a different kernel subsystem. The veth pair is the virtual cable between the container’s network namespace and the host’s. The Linux bridge is the switch that connects the host-side veth to…
Docker networking issues are difficult to diagnose from the host because each container has its own isolated network namespace. The eth0 interface, routing table, and socket state that belong to the container are invisible from the host’s default namespace. The tools that solve this problem are nsenter, which lets you enter the container’s network namespace…
Container storage performance is not the same as host storage performance. The storage driver, the writable layer, and the volume configuration all sit between the application and the disk, and each can become the bottleneck that limits throughput or inflates latency. The diagnostic challenge is that the bottleneck is often not the disk itself: a…
Container system call tracing is complicated by two facts that are easy to overlook. First, minimal container images—the ones most likely to be deployed in production—often exclude strace and other debugging tools precisely because they increase the attack surface . Second, strace relies on the ptrace system call, which requires the CAP_SYS_PTRACE capability that Docker…