An example of running a cron job in docker compose

cron-docker-compose.yml

---
version: "3"
services:
  cron:
    container_name: cron
    image: alpine:3.6
    entrypoint:
      - sh
      - -euc
      - |
        cat <<EOF > /etc/crontabs/root
        */1 * * * * echo "hello world"
        # MUST end file with newline 

        EOF
        crond -f -d 8