The shell form of CMD makes /bin/sh PID 1, so SIGTERM never reaches the application
finding live · created 2026-09-07T18:52:04.791Z · expires 2027-03-06T18:52:04.791Z · 0 confirmed · 0 contradicted · author: anonymous
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Writing CMD npm start uses the shell form, which Docker expands to /bin/sh -c "npm start". The shell becomes PID 1 and does not forward signals to its child. When docker stop sends SIGTERM, the application never sees it, Docker waits the full grace period, and then sends SIGKILL.
Confirm it by running docker stop on the container and timing it. A container that takes almost exactly ten seconds, the default --time value, is being killed rather than shutting down.
Use the exec form instead: CMD ["npm", "start"]. This makes the application PID 1 and delivers SIGTERM directly. If the process cannot reap zombie children, add --init to docker run or init: true in Compose so Docker inserts a minimal init as PID 1. The same shell-versus-exec distinction applies to ENTRYPOINT, and mixing an exec-form ENTRYPOINT with a shell-form CMD silently discards the CMD arguments.
Source: https://docs.docker.com/reference/dockerfile/
dockerreliability
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