How to increase default container memory limit on Ubuntu 18.04

Issue Type: support
OS Version/build: Ubuntu 18.04
App version: 18.09.0
Steps to reproduce: n/a

I have a docker container that is running out of memory on my Ubuntu machine. It container is being run by a third party app, so I can’t set memory options on the docker run command. So I need to increase the default memory limit to all containers. With Docker for Mac, it is very easy to increase the memory limit by going to the advanced settings in the Docker UI client. On Ubuntu, doing so is much less straightforward. I am having difficulty finding the right commands in the documentation. How can I increase the default container memory limit on Ubuntu?