8.2.2.5 Anonymous Dev Pitfalls

Anonymous dev pitfalls describes how anonymous volumes can cause specific confusion during local development, particularly the surprising persistence of stale data across container recreations when a developer assumes a fresh container also means fresh data.

The Common Confusion Scenario

A developer recreating a container, expecting a completely fresh start, may be surprised to find old data still present, because an anonymous volume from a previous run persisted and was reattached.

docker run -d --name dev-db postgres:16
docker exec dev-db psql -c "INSERT INTO test_table VALUES ('old data')"
docker rm dev-db
docker run -d --name dev-db postgres:16
docker exec dev-db psql -c "SELECT * FROM test_table"

Surprisingly, this might return the previously inserted "old data" row, despite the container itself having been entirely removed and recreated — an anonymous volume from the original container may have lingered and been picked up again, or this behavior might otherwise appear inconsistent depending on exact removal flags used.

Why This Is Confusing Specifically During Development

During iterative development and testing, an expectation of starting fresh with each container recreation is common — anonymous volume persistence violating this expectation, without any explicit indication of why, can lead to confusing, hard-to-diagnose test results.

docker rm -v dev-db

Explicitly including the -v flag when removing ensures any associated anonymous volumes are also removed, more reliably achieving the "fresh start" a developer might be expecting.

Establishing a More Predictable Development Pattern

Using --rm for development containers, combined with explicit named volumes only where persistence is genuinely intended, produces more predictable, easier-to-reason-about behavior during iterative development.

docker run -d --rm --name dev-db postgres:16

Why Awareness of Anonymous Dev Pitfalls Matters

Recognizing this specific source of confusing, inconsistent-seeming behavior during development helps developers correctly interpret unexpected data persistence (or its absence), and informs better habits — explicit volume naming, deliberate use of -v during removal — that produce more predictable local development behavior.