cifs volume without clean password

Hello,

Description

I want to create a docker volume without having the clear password displayed with docker volume inspect ....

In the man pages of mount.cifs is the option credentials=filename specified and it works in the following example.

mount -v -t cifs \ 
    -o credentials=$HOME/.cifs,addr=SERVER_IP \
    //SERVER_NAME/SHARE $HOME/MOUNTPOINT

But it will not work with an 'docker volume', which I create with:

docker volume create \
    --driver local \
    --opt type=cifs \
    --opt o=addr=SERVER_IP,credentials=$HOME/.cifs \
    --opt device=//SERVER_NAME/SHARE\
    VOLUME_NAME

After an attempt to run a container with that volume, I get an error message.

> docker container run -it --rm \
    --mount type=volume,source=VOLUME_NAME,target=/data/MOUNTPOINT \
    python:3.8-alpine /bin/sh

docker: Error response from daemon: error while mounting volume '/tmp/virt/docker/65536.65536/volumes/VOLUME_NAME/_data': \
failed to mount local volume: mount //SERVER_NAME/SHARE:/tmp/virt/docker/65536.65536/volumes/VOLUME_NAME \_data, \ 
data: addr=SERVER_IP,credentials=/home/USER/.cifs: invalid argument.

Creating a docker volume with specifying username and password the mount succeeds and I can access the data from within the container.

Start by reproducing the docker volume create command with type=cifs and credentials=$HOME/.cifs, then run the shown docker container run command and inspect the mount error. Compare this with the working username-and-password configuration. Done means the credentials-file form mounts successfully without exposing the clear password in docker volume inspect.