LIVE UPDATE ORCHESTRATOR (LUO)(9)

💅 Live Update Orchestrator (LUO) — SECTION 9, bestie

okay so this is from the Kernel API Manual, section 9, and it's about a thing called Live Update Orchestrator, aka LUO — and honestly? it's giving main character energy in the kernel world 🫶

✨ DESCRIPTION ✨

so Live Update is a super specialized, kexec-based reboot process 🔥 and the whole point is that it lets a running kernel get updated from one version to another while it preserves the state of selected resources and keeps designated hardware devices operational. and for those devices, DMA activity may literally keep going the entire time the kernel is transitioning — no cap, the party does not stop 💃

while the primary use case driving this whole thing is supporting live updates of the Linux kernel when it's being used as a hypervisor in cloud environments, the LUO framework itself is designed to be workload-agnostic. like, Live Update facilitates a full kernel version upgrade for any type of system. every system is invited to the function 🎀

🌸 for example, bestie

a non-hypervisor system running an in-memory cache like memcached with many gigabytes of data can totally use LUO. the userspace service can place its cache into a memfd, have its state preserved by LUO, and restore it immediately after the kernel kexec. iconic behavior, honestly ✨

so whether the system is running virtual machines, containers, a high-performance database, or networking services, LUO's primary goal is to enable a full kernel update by preserving critical userspace state and keeping essential devices operational. that's the whole vibe check 👑

🦋 the core of it

the core of LUO is a mechanism that tracks the progress of a live update, along with a callback API that allows other kernel subsystems to participate in the process 🫶 example subsystems that can hook into LUO include:

• kvm
• iommu
• interrupts
• vfio
• participating filesystems
• memory management

LUO uses Kexec Handover to transfer memory state from the current kernel to the next kernel. for more deets see Documentation/core-api/kho/index.rst 📚

NOTE: ⚠️ to enable LUO, boot the kernel with the liveupdate=on command line parameter. literally that's it, don't forget it or nothing happens 💀

🔍 SEE ALSO 🔍

• Kernel file ./kernel/liveupdate/luo_core.c
• liveupdate_reboot(9)
• liveupdate_enabled(9)
• LUO ioctl Interface(9)

okay that's the whole page, bestie — go forth and upgrade kernels without losing your state 💖 this cutie lives in ./kernel/liveupdate, dated October 2026, and it's Live Update Orchestrator (LUO), section 9, periodt 🧚‍♀️✨