Docker compose always makes a new volume instead of using named ones - docker

Question

My problem is as the title states.
Here are the steps to reproduce. Note I am using docker compose file version 3.3, as I am running this off the apt python version of docker-compose as there is no binary for ARM64.
Create a docker file with these contents:
version: "3.3"
volumes:
owncloud_data:
external: true
owncloud_mysql:
external: true
owncloud_backup:
external: true
owncloud_redis:
external: true
services:
traefik:
image: "traefik"
container_name: "traefik"
restart: "always"
command:
- "--log.level=DEBUG"
- "--api.insecure=true"
- "--providers.docker=true"
- "--providers.docker.exposedbydefault=false"
- "--entrypoints.websecure.address=:443"
- "--certificatesresolvers.myresolver.acme.tlschallenge=true"
#- "--certificatesresolvers.myresolver.acme.caserver=https://acme-staging-v02.api.letsencrypt.org/directory"
# Be sure to have LeGo installed
- "--certificatesresolvers.myresolver.acme.email=<my email>"
- "--certificatesresolvers.myresolver.acme.storage=/letsencrypt/acme.json"
ports:
- "80:80"
- "443:443"
- "8080:8080"
volumes:
- "./letsencrypt:/letsencrypt"
- "/var/run/docker.sock:/var/run/docker.sock:ro"
whoami:
image: "containous/whoami"
container_name: "simple-service"
restart: "always"
labels:
- "traefik.enable=true"
- "traefik.http.routers.whoami.rule=Host(`<my domain>`)"
- "traefik.http.routers.whoami.entrypoints=websecure"
- "traefik.http.routers.whoami.tls.certresolver=myresolver"
owncloud:
image: "owncloud/server"
container_name: "owncloud"
restart: "always"
depends_on:
- db
- redis
environment:
- OWNCLOUD_DOMAIN=owncloud.<my domain>
- OWNCLOUD_DB_TYPE=mysql
- OWNCLOUD_DB_NAME=owncloud
- OWNCLOUD_DB_USERNAME=owncloud
- OWNCLOUD_DB_PASSWORD=owncloud
- OWNCLOUD_DB_HOST=db
- OWNCLOUD_ADMIN_USERNAME=<my username>
- OWNCLOUD_ADMIN_PASSWORD=<my password>
- OWNCLOUD_MYSQL_UTF8MB4=true
- OWNCLOUD_REDIS_ENABLED=true
- OWNCLOUD_REDIS_HOST=redis
healthcheck:
test: ["CMD", "/usr/bin/healthcheck"]
interval: 30s
timeout: 10s
retries: 5
labels:
- "traefik.enable=true"
- "traefik.http.routers.owncloud.rule=Host(`<my domain>`)"
- "traefik.http.routers.owncloud.entrypoints=websecure"
- "traefik.http.routers.owncloud.tls.certresolver=myresolver"
volumes:
- type: volume
source: owncloud_data
target: /owncloud/data
db:
image: webhippie/mariadb:latest
restart: always
environment:
- MARIADB_ROOT_PASSWORD=owncloud
- MARIADB_USERNAME=owncloud
- MARIADB_PASSWORD=owncloud
- MARIADB_DATABASE=owncloud
- MARIADB_MAX_ALLOWED_PACKET=128M
- MARIADB_INNODB_LOG_FILE_SIZE=64M
healthcheck:
test: ["CMD", "/usr/bin/healthcheck"]
interval: 30s
timeout: 10s
retries: 5
volumes:
- type: volume
source: owncloud_mysql
target: /owncloud/mysql
- type: volume
source: owncloud_backup
target: /owncloud/backup
redis:
image: webhippie/redis:latest
restart: "always"
environment:
- REDIS_DATABASES=1
healthcheck:
test: ["CMD", "/usr/bin/healthcheck"]
interval: 30s
timeout: 10s
retries: 5
volumes:
- type: volume
source: owncloud_redis
target: /owncloud/redis
I run this command before I start the containers:
for v in owncloud_data owncloud_mysql owncloud_backup owncloud_redis; do
sudo docker volume create $v
done
I then run sudo docker-compose up.
When I run sudo docker volume ls I get my four (dangling volumes) I created earlier, and 4 more ones that were created from docker compose. What's the deal here? I specified their name explicitly. I'm not sure why the bind for the traefik container works.
I have tried seemingly everything. I put things in quotes. I tried the prepended project name. I tried the short syntax owncloud_data:/owncloud/data. I tried binds, although I don't want to use binds since it's easier to backup a volume.
Thank you, Logan

Answer 1

docker-compose is using the volumes you named, for the binds you specified. However, it is also creating unnamed volumes for each VOLUME declaration on the images you are using and not explicitly binding.
I've made this little script to extract the declared volumes from the images you're using:
images="traefik containous/whoami owncloud/server webhippie/mariadb:latest webhippie/redis:latest"
echo $images | xargs -n1 docker pull
docker inspect $images -f '{{.RepoTags}}, {{.Config.Volumes}}'
The result:
[traefik:latest], map[]
[containous/whoami:latest], map[]
[owncloud/server:latest], map[/mnt/data:{}]
[webhippie/mariadb:latest], map[/var/lib/backup:{} /var/lib/mysql:{}]
[webhippie/redis:latest], map[/var/lib/redis:{}]
None of your binds are binding to the declared volumes, so you're effectively creating new ones and leaving the declared ones empty.