podman build throws an Error: no FROM statement found

I have following Dockerfile to build mysql image under /opt/docker/mysql/Dockerfile.

FROM mysql:5.7
...

And here is db.yml file that uses above file under /opt/docker/db.yml.

# mysql/db yaml
version: '3.7'

volumes:
  foodb: {}

services:
  db:
    build:
      context: ./mysql
      network: host
      args:
        - app_dir=foo
    expose:
       - "3306"
    ports:
       - "3306:3306" # For dev debugging
    volumes:
      - "foodb:/var/lib/mysql"

I launched following podman cmd to build its image.

podman build -f ./db.yml

Then it threw Error: no FROM statement found. From my quick research, I ran into a few saying using old podman may cause this error however I have pretty recent podman and podman-compose installed on rhel 8 server.

podman-compose version: 1.0.6
['podman', '--version', '']
using podman version: 4.4.1

I have to say I was able to build docker image just fine with docker however once I switched to podman I ran into this problem.

I'd greatly appreciate someone can explain to me what causes this error.

You are running podman build command with compose file. You probably need to run podman-compose build instead.

You can run either to use the compose file

podman-compose -f db.yml build

Or you should run build directly using the Dockerfile.

podman build -f mysql/Dockerfile