Production deployment

The default docker compose up is the production stack: built images behind Caddy, with PostgreSQL, Redis, and MinIO. Going live is mostly configuration.

1. Configure .env

cp .env.example .env

Set at minimum:

Variable	Set it to
SITE_ADDRESS	Your domain, e.g. ctf.example.com. Caddy obtains and renews TLS automatically once ports 80/443 are reachable.
PUBLIC_ORIGIN	The browser-facing origin, e.g. https://ctf.example.com. Baked into the frontend at source-build time (release images are same-origin and don’t need the rebuild), and it’s what OIDC redirect URIs and SAML ACS/metadata URLs are built from — so it must be exact if you configure SSO.
JWT_SECRET	A long random value. (Left unset, the app derives a strong per-install secret and persists it — fine for a single host, but set it explicitly for production and always for multi-host.)
POSTGRES_PASSWORD	A real password — generate with openssl rand -hex 24.
MINIO_ROOT_USER / MINIO_ROOT_PASSWORD	Real credentials, same treatment. The backend refuses to start if it finds MinIO’s published defaults on a deployment that looks reachable (non-local PUBLIC_ORIGIN, or MINIO_PUBLIC_ENDPOINT set) — default credentials there mean world read/write on every attachment, outside RBAC entirely.
MINIO_PUBLIC_ENDPOINT	A browser-reachable MinIO host for signed attachment downloads (see below).

Note that MINIO_ROOT_* initialise the MinIO server rather than reconfigure it: changing them after first boot needs docker compose up -d --force-recreate minio, and rotating credentials on a stack that already holds data must also be done inside MinIO.

Full variable semantics: Configuration reference.

2. Open the ports

Map 80 and 443 to the Caddy service (the compose file already declares them; your firewall/cloud rules must allow them). Caddy serves the app on your domain with automatic HTTPS and redirects.

3. Build and start

docker compose up --build -d

On boot the backend applies migrations and seeds the built-in roles; Caddy waits for its health check before routing traffic. Then open your domain and run the setup wizard.

Attachments and MINIO_PUBLIC_ENDPOINT

Challenge files download via pre-signed URLs directly from MinIO, so the browser must be able to reach the MinIO S3 port. Since v1.4.0 the compose binds it to loopback (127.0.0.1:9000) — right for a single-host deploy where everything shares the box. If competitors must reach MinIO on a different host, deliberately publish the port (a compose override changing the binding to 9000:9000, with real MinIO credentials) or front MinIO with its own TLS proxy, and point MINIO_PUBLIC_ENDPOINT at the browser-reachable host:port (e.g. files.example.com:9000) — a non-loopback value also activates the default-credential boot guard. If competitors can’t download attachments, this variable is almost always why.

Upgrades

Prefer pinned release images — every release publishes ghcr.io/tbcsec/flagpost-{backend,frontend}:vX.Y.Z, so upgrading is a tag bump instead of a source rebuild. Building from source (git pull && docker compose build && docker compose up -d) still works. Either way, migrations run automatically on start; take a platform export and a pg_dump first — cheap insurance.

The full story — image overrides, version reporting, release notes, security advisories, and the update check — is on Releases & upgrades.

Scaling expectations

The backend runs as a single process by default (WEB_CONCURRENCY=1): in-process WebSocket broadcast, no Redis needed for realtime, the one-command deploy unchanged. A single decent VM comfortably runs typical CTFs — in published load tests, one worker on 4 vCPU held ~200 concurrent users.

Since v1.4.0, a busy event on a multi-core host can scale out to multiple worker processes on the same box: set WEB_CONCURRENCY>1 in .env and the entrypoint starts that many workers, switches the real-time layer to a Redis-backed cross-worker relay and presence store, splits a fixed DB connection budget across workers, and runs the time-trigger scheduler as a single sidecar. In the 1,500-user A/B, four workers took steady-state 502s from 30–45% to 0%. Multi-machine replicas remain unsupported. The full story — when it helps, how to enable it, and the tuning knobs — is on Scaling for large events; for very large events, rehearse with realistic load first.

Health and monitoring

GET /api/health returns 200 when the app is up (the same check the compose healthcheck and Caddy’s start-up gating use) — point your uptime monitoring at it through the front door: https://ctf.example.com/api/health.