Why is my Portainer Docker Compose creating a new volume - docker

Question

I installed Portainer via Docker Compose. I followed basic directions where I created a portainer_data docker volume:
docker create volume portainer_data
Then I used the following Docker Compose file to setup portainer and portainer agent:
version: '3.3'
services:
portainer-ce:
ports:
- '8000:8000'
- '9443:9443'
container_name: portainer
restart: unless-stopped
command: -H tcp://agent:9001 --tlsskipverify
volumes:
- /var/run/docker.sock:/var/run/docker.sock
- portainer_data:/data
image: 'portainer/portainer-ce:latest'
agent:
container_name: agent
image: portainer/agent:latest
restart: unless-stopped
volumes:
- /var/run/docker.sock:/var/run/docker.sock
- /var/lib/docker/volumes:/var/lib/docker/volumes
ports:
- "9001:9001"
volumes:
portainer_data:
But then I see this inside Portainer when I look at the volumes:
What is wrong in my configuration that it creates a new volume and ignores the one I setup?
Thanks.

Answer 1

docker by default prepends the project name to volume name, this is an expected behaviour https://forums.docker.com/t/docker-compose-prepends-directory-name-to-named-volumes/32835 to avoid this you have two options you can set project name when you run the docker-compose up or update the docker-compose.yml file to use the external volume you created
version: '3.3'
services:
portainer-ce:
ports:
- '8000:8000'
- '9443:9443'
container_name: portainer
restart: unless-stopped
command: -H tcp://agent:9001 --tlsskipverify
volumes:
- /var/run/docker.sock:/var/run/docker.sock
- portainer_data:/data
image: 'portainer/portainer-ce:latest'
agent:
container_name: agent
image: portainer/agent:latest
restart: unless-stopped
volumes:
- /var/run/docker.sock:/var/run/docker.sock
- /var/lib/docker/volumes:/var/lib/docker/volumes
ports:
- "9001:9001"
volumes:
portainer_data:
name: portainer_data
external: false