Host file not found: inventory/local

[marcelloromani]

Hi,
I feel I must be missing something obvious, but I'm not able to make ansible see the inventory I have in a local file.
I'm using the image like this:

docker run --rm -it williamyeh/ansible:ubuntu16.04 ansible -m ping -i inventory/local all

The response I get is:

 [WARNING]: Host file not found: inventory/local

 [WARNING]: provided hosts list is empty, only localhost is available

 [WARNING]: No hosts matched, nothing to do

The inventory I'm referencing is:

cat ./inventory/local
[mysql]
localhost ansible_port=2222

[jira]
localhost ansible_port=2222

[confluence]
localhost ansible_port=2222

What am I doing wrong?

Thank you