It may not be what fly.io does but there's a walkthrough of the basic idea here https://iximiuz.com/en/posts/from-docker-container-to-bootable-linux-disk-image/

It may not be what fly.io does but there's a walkthrough of the basic idea here https://iximiuz.com/en/posts/from-docker-container-to-bootable-linux-disk-image/ https://iximiuz.com/en/posts/from-docker-container-to-bootab...