What Docker Could Not Execute
Docker started the container, but the configured command or entrypoint was not found in the image PATH or at the specified path.
Fix the container entrypoint or command
Inspect the Dockerfile ENTRYPOINT/CMD and confirm the file exists in the final image, enter the image and check with docker run --rm -it <image> sh then ls -la <path>, and fix permissions in the image build (example with RUN chmod +x /path/to/file).
Manual container debug checklist
Inspect the image entrypoint and command with docker image inspect <image> so you know what Docker is trying to execute.
Start a shell in the image, if possible, and verify the target path exists, has execute permissions, and uses the expected shebang or binary format.
Check whether a bind mount or copied script replaced the original executable with a file that has different permissions or line endings.
Why the Container Could Not Start
Usually this comes down to the binary/script is not present in the image at the expected path, file permissions do not allow execution (chmod +x missing), or the command is correct but depends on a missing runtime/interpreter.
Verify the Container Starts Cleanly
Rebuild the image and re-run the container, and confirm the container process starts and stays running.
How Docker starts containers
This failure happens after Docker has already selected the image and is trying to start the process inside the container. At that point the important questions are whether the entrypoint or command exists at the expected path, whether it is executable, and whether the container filesystem or mounted volume changed what Docker is able to run.
Prevent Container Startup Regressions
To prevent this, add a simple smoke test in CI that runs the image and checks the entrypoint, and prefer absolute paths and ensure scripts have correct line endings and shebang.
Examples
exec: "python": executable file not found in $PATH