v-b1 — Externalize Resources

New concepts (2): external Docker network; named volume for persistence. init.sql seeding is the how of persistence, not a third concept.

What changed from v-b0

• PGDATA now lives in a named external volume (minbase_pgdata) → survives down.
• The stack runs on an external network (minbasenet) you own.

Prerequisites (create the external resources once)

docker network create minbasenet
docker volume  create minbase_pgdata

Run it

docker compose up -d

"Why" sidebar (junior track)

• init.sql runs only when the data directory is empty (first cold start). Once the volume has data, Postgres skips the entrypoint scripts — that's why re-running up does not duplicate seed rows.
• external: true means Compose references but never creates/destroys the resource. docker compose down leaves your data intact; down -v still won't touch an external volume. You must docker volume rm it deliberately.
• Backup awareness (deferred): now that data persists, a real deployment needs a backup story. pg_dump -U postgres app > backup.sql is the one-liner. Automated backups to S3 are Advanced-tier (v-a5) — but never call a stack "production-ready" with zero backup.

Verification

1. Volume + network exist: docker volume ls | grep minbase_pgdata, docker network ls | grep minbasenet.
2. Persistence works (v-b0's failure is fixed):

   curl -X POST http://localhost:3000/candidates -H "Content-Type: application/json" -d '{"name":"Ginny"}'
   docker compose down
   docker compose up -d
   curl http://localhost:3000/candidates

   Ginny is still there now.
3. init.sql does not re-run: the seed rows are not duplicated after restart.

Secrets policy

Local-only dev defaults. The Basic tier keeps clearly-labelled literals so the lesson runs with no setup: devpassword (postgres superuser, inline in compose.yml). They are teaching values: never reuse them anywhere reachable from a network, and never copy them into a real deployment. Every published port in this variant binds to 127.0.0.1 only. Real, random, per-install secrets start at v-b8 (generated by install.sh) and the Intermediate tier (v-i2…v-i5). A committed .env.secret is never acceptable; only *.example files are tracked.

Raw files

Download or view the raw variant source files:

File	Link	Notes
compose.yml	download	docker-compose manifest
init.sql	download	SQL bootstrap / seed
README.md	download	raw Markdown source

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