Resolve "unable to find user nonroot"

This error means the final image references the nonroot user, but the /etc/passwd entry that defines it was not carried into the final build stage. The -dev variants include the nonroot user; distroless runtime variants rely on the entry being present.

Fix A: reference the numeric UID

The nonroot user is UID and GID 65532:

USER 65532:65532

Fix B: carry the passwd entry across stages

COPY --from=builder /etc/passwd /etc/passwd
COPY --from=builder /etc/group /etc/group
USER nonroot

Files copied as root

Files added with COPY default to root ownership. Set ownership explicitly:

COPY --chown=65532:65532 ./app /app

Default user reference

A small number of application-specific images set a different home; check the image's overview page.