pgadmin4 container install: volume mapping not working

Hi list,

I have been using the docker container install of pgAdmin4 for about a
year and half, during which time I tried several times trying to make
volume mapping work, in vein.

Yes, the docker installation is very clean and simple.  But I just could
not make volume mapping to work so that script file saved can be
accessed easily and server connections or any session related history
etc. can be preserved when updating to use the latest container images. 
I hope someone can provide a pointer or two to help me.

Here is what I used to create the instance

docker run --name "pgadmin4.21" \

-p 5050:80 \

-e 'PGADMIN_DEFAULT_EMAIL=pgadmin(at)example(dot)com' \

-e 'PGADMIN_DEFAULT_PASSWORD=123456' \

-d dpage/pgadmin4 \

-v /opt/pgadmin_session:/var/lib/pgadmin \

-v /opt/pgadmin_config:/pgadmin4

Docker Inspection shows the container having

            "Env": [

                "PGADMIN_DEFAULT_EMAIL=pgadmin(at)example(dot)com",

                "PGADMIN_DEFAULT_PASSWORD=123456",

                "PATH=/usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",

                "LANG=C.UTF-8",

                "GPG_KEY=0D96DF4D4110E5C43FBFB17F2D347EA6AA65421D",

                "PYTHON_VERSION=3.7.7",

                "PYTHON_PIP_VERSION=20.0.2",

                "PYTHON_GET_PIP_URL=https://github.com/pypa/get-pip/raw/d59197a3c169cef378a22428a3fa99d33e080a5d/get-pip.py",

                "PYTHON_GET_PIP_SHA256=421ac1d44c0cf9730a088e337867d974b91bdce4ea2636099275071878cc189e",

                "PYTHONPATH=/pgadmin4"

            ],

            "Cmd": [

                "-v",

                "/opt/pgadmin_session:/var/lib/pgadmin",

                "-v",

                "/opt/pgadmin_config:/pgadmin4"

            ],

Before I start the container instance, I made sure the folders were
accessible

sudo mkdir /opt/pgadmin_session

sudo mkdir /opt/pgadmin_config

sudo chown 5050:5050 /opt/pgadmin_session

sudo chown 5050:5050 /opt/pgadmin_config

sudo chmod -R 777 /opt/pgadmin_session

sudo chmod -R 777 /opt/pgadmin_config

Cheers!

Bo