Where are the mattermost credentials set ???

How can I not find this information ? Seriously, I feel like an idiot asking this but I'm stuck at the login page... Its asking me for login/password.

This is my docker-compose configuration :

version: "2"

services:

  db:
    build: db
    read_only: true
    restart: unless-stopped
    volumes:
      - ./volumes/db/var/lib/postgresql/data:/var/lib/postgresql/data
      - /etc/localtime:/etc/localtime:ro
    environment:
      - POSTGRES_USER=mmuser
      - POSTGRES_PASSWORD=mmuser_password
  app:
    build:
      context: app
      #args:
       #- edition=team
       #- PUID=1000
       #- PGID=1000
    restart: unless-stopped
    volumes:
      - ./volumes/app/mattermost/config:/mattermost/config:rw
      - ./volumes/app/mattermost/data:/mattermost/data:rw
      - ./volumes/app/mattermost/logs:/mattermost/logs:rw
      - ./volumes/app/mattermost/plugins:/mattermost/plugins:rw
      - ./volumes/app/mattermost/client-plugins:/mattermost/client/plugins:rw
      - /etc/localtime:/etc/localtime:ro
    environment:
      # set same as db credentials and dbname
      - MM_USERNAME=mmuser
      - MM_PASSWORD=mmuser_password
      - MM_DBNAME=mattermost
      # in case your config is not in default location
      #- MM_CONFIG=/mattermost/config/config.json

  web:
    build: web
    ports:
      - "8080:80"
      - "8443:443"
    read_only: true
    restart: unless-stopped
    volumes:
      # This directory must have cert files if you want to enable SSL
      - ./volumes/web/cert:/cert:ro
      - /etc/localtime:/etc/localtime:ro
    # Uncomment for SSL
    # environment:
    #  - MATTERMOST_ENABLE_SSL=true

I tried mmuser and mmuser_password as last resort but it didn't work.

Ok, so you don't have to create the users yourself...
My DB was unhealthy and this was preventing the application to redirect me toward the signup page (Instead took me to the login page!).

The following docker-compose is working for me. Hope it can help someone else:

version: "2"

services:

  db:
    build: db
    read_only: true
    restart: unless-stopped
    #volumes:
      #- ./volumes/db/var/lib/postgresql/data:/var/lib/postgresql/data
      #- /etc/localtime:/etc/localtime:ro
    environment:
      - POSTGRES_USER=mmuser
      - POSTGRES_PASSWORD=mmuser_password
      - POSTGRES_DB=mattermost
    # uncomment the following to enable backup
    #  - AWS_ACCESS_KEY_ID=XXXX
    #  - AWS_SECRET_ACCESS_KEY=XXXX
    #  - WALE_S3_PREFIX=s3://BUCKET_NAME/PATH
    #  - AWS_REGION=us-east-1

  app:
    build:
      context: app
      # uncomment following lines for team edition or change UID/GID
      # args:
      #   - edition=team
      #   - PUID=1000
      #   - PGID=1000
    restart: unless-stopped
    #volumes:
      #- ./volumes/app/mattermost/config:/mattermost/config:rw
      #- ./volumes/app/mattermost/data:/mattermost/data:rw
      #- ./volumes/app/mattermost/logs:/mattermost/logs:rw
      #- ./volumes/app/mattermost/plugins:/mattermost/plugins:rw
      #- ./volumes/app/mattermost/client-plugins:/mattermost/client/plugins:rw
      #- /etc/localtime:/etc/localtime:ro
    environment:
      # set same as db credentials and dbname
      - MM_USERNAME=mmuser
      - MM_PASSWORD=mmuser_password
      - MM_DBNAME=mattermost
      # in case your config is not in default location
      #- MM_CONFIG=/mattermost/config/config.json

  web:
    build: web
    ports:
      - "8080:80"
      - "8443:443"
    read_only: true
    restart: unless-stopped
    #volumes:
      # This directory must have cert files if you want to enable SSL
      #- ./volumes/web/cert:/cert:ro
      #- /etc/localtime:/etc/localtime:ro
    # Uncomment for SSL
    # environment:
    #  - MATTERMOST_ENABLE_SSL=true