Docker starting container process caused “exec: \”arg\“: executable file not found in $PATH”: unknown.

Question

My task is to create Dockerfile such that it works the following way:

docker build -t test .
Returns Image named test successfully created

docker run --rm test
Returns Hello world!

docker run --rm test Universe
Returns Hello Universe!

What I have so far:
Dockerfile

FROM ubuntu:14.04

LABEL maintainer="trthhrtz"

CMD if [ $# -eq 0 ]; then echo "Hello world!"; else echo "Hello " + $@ + "!"; fi

It does not work in case of input arguments, the error is:
docker: Error response from daemon: OCI runtime create failed: container_linux.go:348: starting container process caused "exec: \\"Universe\\": executable file not found in $PATH": unknown.
ERRO[0000] error waiting for container: context canceled

Answer 1

It would be easier to:

• define an entrypoint script entrypoint.sh with your command logic scripted in it.
• COPY that file in your Dockerfile
• leave CMD undefined

That way, any additional parameter to your docker run -it --rm myImage arg1 arg2 ... command will be passed to the bash entrypoint.sh script, which will interpret $@ correctly, as illustrated in " What does set -e and exec "$@" do for docker entrypoint scripts? ".
See " Passing arguments from CMD in docker " for more.

Answer 2

Make sure you have a correct order of arguments when you do docker command .

For example:

docker run --name test-ubuntu -it d37f4165b5d2 bash
instead of
docker run --name test-ubuntu d37f4165b5d2 -it bash