Run nomad task inside existing container from different task (Nomad how to backup database)

I have database task which was run by nomad. I need to backup database periodically. I want to use WAL journal to do this: envdir /etc/wal-e.d/env wal-e --terse backup-push.

So I want to know how to run this command inside existing container with help of periodic nomad’s job?

UPD. I found how this container is named Drivers: Docker | Nomad | HashiCorp Developer, but did not find yet how to fetch that value.