How to use Docker Volumes? - django

Question

I am completely new to Docker, right now I am using an open-source tool, which is a Docker application, I need to make some changes to the existing application for my requirement and it should reflect the changes, I did a lot of searching, then I found that we can do this with the help of Docker Volumes, but I am unable to follow any of the articles on the web as well as documentation? Any suggestions will be appreciated.
docker-compose.yml:
version: "3.3"
services:
cvat_db:
container_name: cvat_db
image: postgres:10-alpine
networks:
default:
aliases:
- db
restart: always
environment:
POSTGRES_USER: root
POSTGRES_DB: cvat
POSTGRES_HOST_AUTH_METHOD: trust
volumes:
- cvat_db:/var/lib/postgresql/data
cvat_redis:
container_name: cvat_redis
image: redis:4.0-alpine
networks:
default:
aliases:
- redis
restart: always
cvat:
container_name: cvat
image: cvat/server
restart: always
depends_on:
- cvat_redis
- cvat_db
build:
context: .
args:
http_proxy:
https_proxy:
no_proxy: nuclio,${no_proxy}
socks_proxy:
USER: "django"
DJANGO_CONFIGURATION: "production"
TZ: "Etc/UTC"
CLAM_AV: "no"
environment:
DJANGO_MODWSGI_EXTRA_ARGS: ""
ALLOWED_HOSTS: '*'
CVAT_REDIS_HOST: "cvat_redis"
CVAT_POSTGRES_HOST: "cvat_db"
volumes:
- cvat_data:/home/django/data
- cvat_keys:/home/django/keys
- cvat_logs:/home/django/logs
- cvat_models:/home/django/models
cvat_ui:
container_name: cvat_ui
image: cvat/ui
restart: always
build:
context: .
args:
http_proxy:
https_proxy:
no_proxy:
socks_proxy:
dockerfile: Dockerfile.ui
networks:
default:
aliases:
- ui
depends_on:
- cvat
cvat_proxy:
container_name: cvat_proxy
image: nginx:stable-alpine
restart: always
depends_on:
- cvat
- cvat_ui
environment:
CVAT_HOST: localhost
ports:
- "8080:80"
volumes:
- ./cvat_proxy/nginx.conf:/etc/nginx/nginx.conf:ro
- ./cvat_proxy/conf.d/cvat.conf.template:/etc/nginx/conf.d/cvat.conf.template:ro
command: /bin/sh -c "envsubst '$$CVAT_HOST' < /etc/nginx/conf.d/cvat.conf.template > /etc/nginx/conf.d/default.conf && nginx -g 'daemon off;'"
networks:
default:
ipam:
driver: default
config:
- subnet: 172.28.0.0/24
volumes:
cvat_db:
cvat_data:
cvat_keys:
cvat_logs:
cvat_models:

Answer 1

Docker volumes are mostly used as a way to save data outside of your container. If you mount a volume and store data in it, the data will not be erased when the container is destroyed. In order to mount a volume, you have to add -v <directory in your machine>:<directory in your container> to your docker run command. It may fulfill your requirements, but it most likely wont be enough.
If your assignment requires you to change for instance the behaviour of the application, then you have to rebuild the docker image and use it in your docker-compose.yml