How to create and use a compose YAML files for Stacks

The stack file is a YAML file, and is basically the same thing as a Docker Compose file. Both are YAML files that define a Docker base application. Technically, a stack file is a compose file that requires a specific version (or above) of the compose specification. Only the version 3.0 specification and above are supported by Docker stacks. If you have an existing project that uses Docker compose YAML files, and those files are using the version 2 or older specification, then you will need to update the YAML files to the version 3 spec to be able to use them with Docker stacks. It is worth noting that the same YAML file can be used with either Docker stacks or Docker compose (provided it is written using the version 3 specification or higher). However, there are some instructions that will be ignored by one or the other tools...