David Heinemeier Hansson

ONCE: Run Multi Dockerized Web Apps on Single Server

The video introduces Once, a platform that lets developers run several Docker‑containerized web applications on a single machine—whether a laptop, on‑prem server, or cloud VM. Installation is reduced to a one‑liner curl command that auto‑detects the host OS and pulls Docker if needed, after which users can select from pre‑packaged apps or supply custom images. Key insights include a unified control panel displaying CPU, memory, and disk allocation per app, simple hostname configuration, and built‑in health‑check logic that ensures zero‑downtime rollouts. The demo walks through deploying three stock apps—Campfire (chat), Writebook (manuals), and Fizzy (Kanban)—and shows how to configure external services like SMTP for email‑enabled containers. It also highlights the ability to script custom Go‑based wikis and even a single‑page snake game, pushing images to GitHub Packages for automated CI/CD. Notable examples feature the rapid spin‑up of chat.localhost, the manual adjustment of package visibility to make containers public, and live log streaming from the dashboard. The presenter demonstrates updating an app by editing source code, rebuilding the Docker image, and letting Once replace the running instance without interrupting users, while also exposing troubleshooting steps when health checks fail. The broader implication is that Once abstracts much of the DevOps overhead, enabling AI‑generated or hobby projects to be deployed, monitored, and updated with minimal friction. Small teams and solo developers can consolidate resources, maintain consistent backups, and scale from local testing to production clouds without rewriting deployment pipelines.