## What this teaches

How to can't start Marqo on arm64.

## The problem

Issue marqo-ai/marqo#433 (closed, 5 comments): **Describe the bug** Hi there! After successfully testing Marqo on an Intel machine, I'm now trying - but failing - to get Marqo working on an arm64 server. I've followed the [arm64 installation steps](https://github.com/marqo-ai/marqo#m-series-mac-users) in the README, but can't get it to work... **To Reproduce** Start Marqo-OS container: ``` docker rm -f marqo-os;

## What worked (verified answer)

If Marqo starts on arm64 but the container crashes with 'Can't connect to Marqo-os backend' while OpenSearch runs fine, check your host firewall. The reporter's UFW was blocking container-to-container traffic to the OpenSearch container, and adjusting the firewall fixed it.

## Source

gh:marqo-ai/marqo#433 - https://github.com/marqo-ai/marqo/issues/433