ERROR: In file ‘docker-compose.yaml’ must be a mapping not an array

General
1

Hi

I have a code line in my .yaml file:

services:
    volumes:
        - ./data/postgres:/var/lib/postgresql/data

When I attempt to docker compose the file, I get the following error message:

## ERROR: In file ‘./joplin-docker-compose.yaml’, service ‘volumes’ must be a mapping not an array.

I read from another thread that the syntax is wrong:

services:
    volumes:
        - myVolume: {}

Did not work, however:

services:
    volumes:
        myVolume: {}

this worked.

When I attempt that syntax with my file:

services:
    volumes:
        ./data/progress:/var/lib/postgresql/data

I get the following error message:

## ERROR: In file ‘./joplin-docker-compose.yaml’, service ‘volumes’ must be a mapping not a string.

I believe my formatting is correct: ‘volumes:’ is indented by four spaces, ‘-./data/postgres:/var/lib/postgresql/data’ is indented by 8 spaces.

I do not know what is wrong with either my syntax or my data. Does anyone have an idea of what the issue is, and can somebody give me a link in the documentation for the compose .yaml file structure and requirements?

2

That could hardly be called “service”. You have to define a service and volumes are defined fo the service.

Assuming this was just a code snippet and you have defined an image as well:

services:
  postgres:
    volumes:
      - ./data/postgres:/var/lib/postgresql/data
    # rest of the parameters
3

I have rewritten my compose file:


version: ‘3.0’

services:
    db:
        image: postgres:latest
    volumes:
        - todo-postgres-data:/var/lib/postgresql/data
    ports:
        - “5432:5432”
    restart: always
    environment:
        - POSTGRES_PASSWORD=secret
        - POSTGRES_USER=joplin-user
        - POSTGRES_DB=joplindb
    app:
        image: joplin/server:latest
    container_name: joplin-server
    depends_on:
        - db
    ports:
        - “8080:8080”
    restart: always
    environment:
        - APP_PORT=8080
        - APP_BASE_URL=https://localhost
        - DB_CLIENT=pg
        - POSTGRES_PASSWORD=secret
        - POSTGRES_DATABASE=joplindb
        - POSTGRES_USER=joplin-user
        - POSTGRES_PORT=5432
        - POSTGRES_HOST=db
volumes:
    todo-postgres-data

However, this fails with a similar error:

parsing joplin-docker-compose.yaml: yaml: line 18: block sequence entries are not allowed in this context

The command I am using to run my compose file is:

docker compose -f joplin-docker-compose.yaml up
4

Again, it’s pretty obvious that only the first line was indented under the services.

5

The compose specification is always a good starting point in case something is unclear: https://docs.docker.com/compose/compose-file/