With IBM's mainframe the reason it's possible is because there is the underlying IBM OS running underneath.
See: http://linuxtoday.com/news_story.php3?ltsn=2002-08-27-014-26-NW-HE-SV Hugh McColl wrote: > David Kirk wrote: > >>> >>> (btw, I once heard of some people trying to change the running kernel >>> without >>> rebooting... and I think there was some discussion on it on here a >>> while ago? >>> if anyone knows more I'd be interested :) >> >> > I recall a recent discussion were someone mentioned replacing a kernel > without rebooting on an IBM Z-Series. Is that the one? > > It's my understanding that on a Z-Series (or s390) you can run an > instance of a Linux O/S in a native LPAR (logical partition) or multiple > instances as VMs (Virtual Machines) in an LPAR. And you can partition a > machine into multiple LPARS etc. and of course each O/S instance can be > a different version (or even a different distro) . So sure you can > replace and restart instances of linux without 'rebooting' the physical > machine. > If we are talking about dynamically replacing an instance of a running > [linux] kernel while allowing services and applications it's hosting to > continue running (slight pause allowed), then I suspect that will be a > tricky one to pull off :-) I too would be interested in hearing more on > this subject.. > > > > >
