CBL-Mariner is an internal Linux distribution for Microsoft’s cloud infrastructure and edge products and services. CBL-Mariner is designed to provide a consistent platform for these devices and services and will enhance Microsoft’s ability to stay current on Linux updates. This initiative is part of Microsoft’s increasing investment in a wide range of Linux technologies, such as SONiC, Azure Sphere OS and Windows Subsystem for Linux (WSL).
Source: GitHub – microsoft/CBL-Mariner: Linux OS for Azure 1P services and edge appliances