How to create docker volume device/host path

Question

I believe there is an easy way to copy files into a docker volume that has already been mounted to a container.

docker cp /tmp/my_data/. my_container:/my_data as referenced by How to copy multiple files into a docker data volume

But, how does one create a named volume using docker volume create --name my-volume that already has files in it? I have read that it's not a good idea to cp files into the {{.Mountpoint}}.

I'm new to docker and all of it's nuancies, so apologies if my fundamental understanding of volumes is incorrect.

Answer 1

Approach #1 - COPY

To copy the file from the host to the container

docker cp /path/of/the/file <Container_ID>:/path/of/he/container/folder

Issue with the above approch is, it will not persists the volume or file or dir, as you remove the container it will be lost. This is suggested only for temporary pupose.

Approach #2 - Volume Mounting

Mouting the volume from the host to container

Step1: Create the volume with the custom path

docker volume create --name my_test_volume --opt type=none --opt device=/home/jinna/Jinna_Balu/Test_volume --opt o=bind

Step2 : Mount to the container or swarm service

docker run -d \
  --name devtest \
  --mount source=my_test_volume,target=/app \
  nginx:1.11.8-alpine

We can do both of the above steps with below .yaml files

version: '3'
services:
  nginx:
    image: nginx:1.11.8-alpine
    ports:
      - "8081:80"
    volumes:
      - my_test_volume:/usr/share/app
volumes:
  my_test_volume:
    driver: local
    driver_opts:
       o: bind
       type: none
       device: /home/jinna/Jinna_Balu/Test_volume

RUN the above yml with docker-compose

docker-compose up -d

NOTE: create the folder path before you do docker-compose.

Good practice to have files mouted to maintain the persistency.