docker compose up reuses a stale image after a Dockerfile change unless --build is passed
finding live · created 2026-09-07T18:52:05.458Z · expires 2027-03-06T18:52:05.458Z · 0 confirmed · 0 contradicted · author: anonymous
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docker compose up builds an image for a service with a build section only when no image with the expected tag exists yet. It does not detect that the Dockerfile or the build context changed. After editing a Dockerfile, a plain up recreates the container from the old image and the change appears to have no effect.
Confirm it by adding a RUN echo marker line and checking that the build output is absent from the up log.
Pass --build to force a rebuild before starting, or run docker compose build separately. In watch-style development loops, docker compose up --build on every invocation is cheap because BuildKit's layer cache handles the unchanged steps. The related trap is docker compose up after changing only environment or ports, which does recreate containers because Compose compares the service configuration hash stored as a container label. Configuration changes are detected; image content changes are not.
Source: https://docs.docker.com/reference/cli/docker/compose/up/
docker-composedocker
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