[SOLVED] WARN[0000] The "MYSQL_USER" variable is not set. Defaulting to a blank string

[rimelek (Ákos Takács)]

@bluenobly is right. If you need even more details, I found three topics where I explained the different ways to pass variables (compose --env-file, .env file, env_file in compose files)

• Specifying buildtime envars for docker-compose with multitiple files - #3 by rimelek
• Combining docker-compose override files with mutliple .env files - #2 by rimelek
• Passing command line arguments in Docker Compose - #2 by rimelek
  This one is just a use case for multiple .env files.