Rails Learning Lab¶

Date: 2026-08-01 Hostname: docker-host IP address: 192.168.0.110 Location: /opt/rails-lab URL: http://192.168.0.110:3300

A disposable Ruby on Rails 8 + PostgreSQL sandbox used for learning. Not a production service: no reverse proxy, no backups, no Komodo management. The point is a real app to poke at - rails console, migrations, request tracing.

Stack¶

Container	Image	Port	Role
`rails-lab-web`	built from `ruby:3.4-slim`	3300 -> 3000	Rails 8.1.3.1 dev server
`rails-lab-db`	`postgres:17-alpine`	internal 5432	Development database

Named volumes: rails-lab_pgdata (database), rails-lab_bundle (gems). The generated Rails app lives in /opt/rails-lab/app, bind-mounted into the container at /app.

Why port 3300¶

Port 3000 is taken by BentoPDF, and 3001-3006 plus 3008-3009 are taken by Homelable, Homepage, DocuSeal, Form, Dawarich, Kan, Portfolio and Topology. The first deploy failed with Bind for 0.0.0.0:3000 failed: port is already allocated, so the lab moved to 3300.

Rails 8 host authorization¶

Rails blocks non-localhost requests in development mode. The compose file sets:

RAILS_DEVELOPMENT_HOSTS: "192.168.0.110,.local,.lan,.ts.net"

Without this, browsing to the LAN IP returns "Blocked hosts" instead of the app.

Source of truth¶

The compose file, Dockerfile and bootstrap script are not in this repo. They live in the learning workspace on LXC 109:

/root/learning/rails/lab/
  Dockerfile
  compose.yaml
  bootstrap.sh
  README.md

Deployed with scp -r to /opt/rails-lab. Kept out of compose/ because it is throwaway learning infrastructure, not a homelab service - same reasoning as Odysseus being a files_on_host stack outside the repo.

First-time setup¶

scp -i ~/.ssh/id_ed25519 -r /root/learning/rails/lab root@192.168.0.110:/opt/rails-lab
ssh docker-host
cd /opt/rails-lab
./bootstrap.sh      # builds image, runs `rails new`, creates the database
docker compose up -d

bootstrap.sh is idempotent - it exits early if app/Gemfile already exists.

Daily commands¶

cd /opt/rails-lab
docker compose up -d
docker compose logs -f web
docker compose exec web bin/rails console
docker compose exec web bin/rails routes
docker compose exec web bin/rails db:migrate
docker compose exec web irb          # plain Ruby REPL, no Rails
docker compose down -v               # stop and wipe the database

Editing from VS Code¶

VS Code on the Nobara desktop connects over Remote-SSH:

Ctrl+Shift+P -> Remote-SSH: Connect to Host -> docker
Open folder /opt/rails-lab/app

The docker alias already existed in Nobara's ~/.ssh/config. On 2026-08-01 Nobara's public key was appended to /root/.ssh/authorized_keys on docker-host - before that, Remote-SSH failed with Permission denied (publickey).

Rails reloads changed code automatically in development mode, so saving in VS Code is enough - no container restart.

Notes¶

The stack has restart: unless-stopped, so it survives host reboots
Gems install at runtime into a named volume rather than at image build time. Slower first boot, but no rebuild needed when the Gemfile changes
To start over completely: docker compose down -v && rm -rf /opt/rails-lab/app