I'm sharing this as there's only a single mention of this in the entire AWS ECS documentation; and no hint in the console UI.
If you attempt to run a one-off task in ECS, for example
python manage.py migrate, you might see a cryptic error message like this:
Status reason CannotStartContainerError: API error (404): invalid header field value "oci runtime error: container_linux.go:247: starting container process caused "exec: \"python manage.py migrate\": executable file not found in $PATH"\n"
Command ["python manage.py migrate"]
After searching many unrelated GitHub issues, fiddling with the aws-ecs tool and just attempting to inject likely looking strings into the command field; I eventually stumbled on a single example in the AWS documentation.
For Command override, type the command override to send. If your container definition does not specify an ENTRYPOINT, the format should be a comma-separated list of non-quoted strings.
The trick is to replace spaces (outside of quoted strings) with commas. For example, our earlier command becomes
I suspect the reason for this is that in a Dockerfile the format is:
CMD ["python", "manage.py", "migrate"]. In fact, this is what the command object (as in the example above) is translated to.
Hope this helped!