Believe it or not, today Linux is right at the core of Microsoft Azure's infrastructure, on the very nodes that run all those fancy virtual machines. Getting there was not easy, and a lot of work was needed to meet the very stringent security and performance goals that were set. We built a custom distribution, added several security features such as signed dm-verity and kernel-enforced code integrity, came up with a way to keep state alive across kexec with PMEM, and implemented the stackable Portable Services image model that ultimately became sysexts and confexts. And much more! This talk will walk through this effort, starting with a peek under the cover at the hardware that powers it and what it enables, passing through the custom OS and ending up at all the features we added to systemd and elsewhere that you all can enjoy as well.