volumes 

(OPTIONAL)
This is a definition of volumes. Using the variables you can set the path of the container as well as the size. The volume size have to be a multiple of 8.

Example:

{"volumes":[ 
  {
    "container_path":"/var/lib/mysql",
    "size": "8GB"
  }
 ]
}

Learn more about volumes here.

Did this answer your question?