Messages in this thread |  | | From | (Alan Cox) | Subject | Re: Core dumps & restarting | Date | Tue, 29 Oct 1996 22:14:49 +0000 (GMT) |
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> What about the system save-state that SCO uses to recover from UPS initiated > shutdown? They write out the machine state into the swap partition. > When you restart your system, it picks up right where it left off. Nice.
Thats an application of the "process can do is own shutdown logic", just applied to the kernel. You swap everything out (SCO guarantees it will all fit - we'd have to keep an extra reserve for that as we handle swap differently). You write out the entire kernel memory image, all the ram the lot. When you boot you pick up the log, load the entire image except for a small workspace area you always keep (remember the kernel code segment is constant), recover the registers and continue. That kind of trick isnt hard to do (people were doing it with game 'backup' utilities on 8bit micros).
People take that further at the high end continous running systems as you install a kernel upgrade, save the entire system state to swap, switch to the new kernel and recover it - with no down time and not even dropping network connections.
Alan
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