Docker error: invalid reference format: repository name must be lowercase

Question

Ran into this Docker error with one of my projects:

invalid reference format: repository name must be lowercase

What are the various causes for

Answer 1

Replacing image: ${DOCKER_REGISTRY}notificationsapi with image:notificationsapi or image: ${docker_registry}notificationsapi in docker-compose.yml did solves the issue

file with error

  version: '3.4'

services:
  notifications.api:
    image: ${DOCKER_REGISTRY}notificationsapi
    build:
      context: .
      dockerfile: ../Notifications.Api/Dockerfile

file without error

version: '3.4'

services:
 notifications.api:
    image: ${docker_registry}notificationsapi
    build:
      context: .
      dockerfile: ../Notifications.Api/Dockerfile

So i think error was due to non lower case letters it had