[kccqzy]

But do you update the kernel without rebooting? Previously transactional-update can update the kernel and call dracut to make a new boot image. I suppose this still needs a reboot?

[scns]

Canonical and Oracle offer updating a running Kernel as a paid service IIRC. One was called Ksplice, i think the one Oracle acquired.

[teo_zero]

Please be aware that ksplice can only apply small patches to a running kernel. It can't replace the entirety of it with a new version.

[carlsborg]

No reboots for non-kernel updates would still be a win imho. Because these are rolling releases not point releases, and updates snapshots are pulled daily by default (and therefore daily reboots are/were recommended), so its likely only a small subset of snapshots have a kernel update.