Re: Switching Kernels without Rebooting?

[Kai Henningsen]

[e-mail] (Rik van Riel)  wrote on 11.07.01 in <[e-mail]>:

> One thing which always surprises me in this discussion
> (it comes up about once a year, it seems) is that
> nobody participating in this discussion ever starts
> writing any code for it.
>
> Is this a feature which is only wanted by people who
> don't want to code, or is this just a signal that the
> amount of trouble involved just isn't worth it?

Maybe it's a sign that the people who *would* be able to contribute have  
all looked at the problem already (surely most people are annoyed how a  
reboot interrupts everything), and have already concluded for themselves  
that it's not possible with reasonable effort ... but there is a steady  
influx of new people who don't understand enough of the problem and have  
to ask.

What I'd *really* like (but don't see how to get there) would be a "save  
system state, shutdown, change kernel and/or hardware, reboot, restore  
state" system (where state is like "I'm logged in on this console, in this  
current directory, and under X I have Netscape running and this page  
displayed" but I don't care about the exact state of Squid or even if my  
ISDN line is dialled in, because those "fix themselves").

I suspect to do this right would need a means of storing per-process state  
controlled by the process (because only that process knows what needs to  
be saved, and what can easily be reconstructed - for example, open file  
descriptors to a place where we store cookies don't need to be saved, just  
routinely reopened), and then every user-visible non-transient program  
needs to implement it - and I don't see *that* happen in the next ten  
years.

But it *does* have the advantage of not needing to save kernel-internal  
state.

MfG Kai