Failed to get CA_CONTAINER_ID

[makotonakai]

When I executed ./create_secret_ca.sh, I failed to copy the secrets from the container to my local environment.

"docker cp" requires exactly 2 arguments.
See 'docker cp --help'.

Usage:  docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH|-
	docker cp [OPTIONS] SRC_PATH|- CONTAINER:DEST_PATH

Copy files/folders between a container and the local filesystem
"docker cp" requires exactly 2 arguments.
See 'docker cp --help'.

Usage:  docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH|-
	docker cp [OPTIONS] SRC_PATH|- CONTAINER:DEST_PATH

It turned out that this error was caused by the fact that export CA_CONTAINER_ID=$(docker ps -a --filter name=ca -q) returned more than one IDs, because it retrieved all the containers whose names include "ca".