How is Docker Compose version 2 “volumes” syntax supposed to look?

Purpose of the volumes key

It is there to create named volumes.

If you do not use it, then you will find yourself with a bunch of hashed values for your volumes. Example:

$ docker volume ls 
DRIVER              VOLUME NAME
local               f004b95d8a3ae11e9b871074e9415e24d536742abfe86b32ffc867f7b7063e55
local               9a148e167e1c722cbdb67c8edc36f02f39caeb2d276e9316e64de36e7bc2c35d

With named volumes, you get something like the following:

$ docker volume ls
local               projectname_someconf
local               projectname_otherconf

How to create named volumes

The docker-compose.yml syntax is:

version: '2'

services:
    app:
        container_name: app
        volumes_from:
            - appconf
    appconf:
        container_name: appconf
        volumes:
            - ./Docker/AppConf:/var/www/conf

volumes:
    appconf:

networks:
    front:
        driver: bridge

This something like above shown named volumes.

How to remove volumes in bulk

When you have a bunch of hashes, it can be quite hard to clean up. Here’s a one-liner:

docker volume rm $(docker volume ls |awk '{print $2}')

Edit: As @ArthurTacca pointed out in the comments, there’s an easier to remember way:

docker volume rm $(docker volume ls -q)

How to get details about a named volume

Now that you do not have to look up hashes anymore, you can go on it and call them by their … name:

docker volume inspect <volume_name>

# Example:
$ docker volume inspect projectname_appconf

[
    {
        "Name": "projectname_appconf",
        "Driver": "local",
        "Mountpoint": "/mnt/sda1/var/lib/docker/volumes/projectname_appconf/_data"
    }
]

Sidenote: You might want to docker-compose down your services to get a fresh start before going to create volumes.

In case you are using Boot2Docker/ Docker Machine, you will have to docker-machine ssh and sudo -i before doing a ls -la /mnt/… of that volume – you host machine is the VM provisioned by Docker Machine.

EDIT: Another related answer about named volumes on SO.