Every article tagged Docker, in one place.
Showing 12 articles
Docker packages an application with everything it needs (runtime, libraries, config) into an image . Running an image creates a container : an isolated process that behaves the same on your laptop, a CI runner and a production server. Images vs containers An i...
A Dockerfile that "works" and one that's good for production differ in image size, build speed, security and how the app shuts down. Here's a solid template. # syntax=docker/dockerfile:1 # ---------- dependencies (all, for building) ---------- FROM node:22-alp...
Docker Compose describes a multi-container setup in one file. One command starts your API, database, cache and anything else the project needs, the same way on every developer's machine. compose.yaml services: api: build: . ports: - "3000:3000" environment: DA...
Smaller images pull faster, start faster, cost less to store and contain fewer packages with vulnerabilities. Going from 1.2 GB to under 200 MB is common. 1. Choose a smaller base image node:22 (Debian full) - large, has build tools. node:22-slim - Debian with...
Most "it can't connect" problems with Docker come from a few networking rules. Once you know them, they're easy to reason about. User-defined bridge networks docker network create appnet docker run -d --name db --network appnet -e POSTGRES_PASSWORD=secret post...
Slow Docker builds usually re-download dependencies that haven't changed. BuildKit, the default builder in modern Docker, has features designed to stop that. 1. Order layers from least to most frequently changed COPY package.json package-lock.json ./ # changes...
Containers isolate processes, but a careless image or run command can undo most of that protection. These practices close the common gaps. 1. Don't run as root RUN addgroup -S app && adduser -S app -G app USER app If an attacker exploits your app, they get the...
A common pipeline: every push to main builds an image, tags it with the commit and pushes it to a registry, ready to deploy. The workflow name: Docker image on: push: branches: [main] tags: ['v*'] permissions: contents: read packages: write # push to ghcr.io j...
A running process isn't necessarily a working one. It might be deadlocked, out of database connections or stuck in a crash loop. Health checks and restart policies help Docker notice and react. HEALTHCHECK in a Dockerfile HEALTHCHECK --interval=30s --timeout=3...
A production FastAPI deployment is usually a container running an ASGI server behind a reverse proxy or load balancer. Dockerfile FROM python:3.13-slim # uv for fast, reproducible installs COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv WORKDIR /...
When a container doesn't behave, work from the outside in: what does it log, how did it exit, what does its configuration look like, and what is happening inside? 1. Logs docker logs api # everything written to stdout/stderr docker logs -f --tail 100 api # fol...
Containers are disposable, but data often isn't. Docker offers three ways to give a container storage beyond its own temporary layer. Named volumes docker volume create pgdata docker run -d -v pgdata:/var/lib/postgresql/data postgres:17 docker volume ls docker...
