Glossary

Bind mount — a container path mapped to a path on your machine (./html:/usr/share/nginx/html). You edit the files; the container reads them. See Volumes and Bind Mounts.

Build context — the directory sent to Docker when building an image (build: .). Keep it small; a .dockerignore file excludes the junk.

Compose file — the YAML file (compose.yaml) describing your stack. The thing this whole guide is about.

Container — a running instance of an image. The process, isolated.

depends_on — declares start order between services. Order only — not readiness (that's what healthchecks are for). See Depends-On and Healthchecks.

Environment variable — a KEY=value setting passed into a container. Configuration without rebuilding. See Environment Variables.

Healthcheck — a command Compose runs inside a container to decide if it's actually ready (pg_isready, curl -f .../health). Makes depends_on meaningful.

Image — the frozen template a container starts from (postgres:16). Built from a Dockerfile or pulled from a registry.

Interpolation — ${VAR} in the compose file, filled in from the shell or .env at load time. With :-default and :?error modifiers.

Named volume — Docker-managed persistent storage (pgdata:/var/lib/postgresql/data), declared in the top-level volumes: block. Survives down; deleted by down -v.

Network — virtual LAN for your project's containers. Compose makes one per project; services find each other by service name. See Networks.

Orchestration — running containers across many machines (Kubernetes, Swarm). Compose is not this; Compose is one machine, well.

Port publishing — mapping a container port to a host port ("8080:80") so the outside world can reach in. See Ports.

Profile — an opt-in label on a service (profiles: [tools]). Profiled services only start with --profile or COMPOSE_PROFILES. See Profiles.

Project — everything in one compose file, managed as a unit. Named after the directory by default (override with --project-name / COMPOSE_PROJECT_NAME).

Recreate — Compose's update mechanism: stop the old container, start a new one from the current file/image. Data in volumes is untouched.

Restart policy — what happens when a container exits (unless-stopped, on-failure, always, "no"). See Services.

Service — one container's recipe in the compose file: image/build, ports, volumes, environment, and friends. The hostname other services use to reach it.

YAML — the indentation-based format of the compose file. Two spaces per level, never tabs, quote your port mappings.