[CALUG] Saving/restoring process states

[James Ewing Cottrell 3rd]

junekis at comcast.net wrote:

>What you are wanting to do is often refered to as checkpoint/restore
>
>It was a practice that was common back when computers were slow and unreliable and processes ran for a long time before completing.
>
>Checkpoint/restore let a user recover part of the work that had been done in the event of a machine crash.
>  
>
Right. The old OSs were rather monolithic. With the advent of minis and 
micros, the OS was often minimal, and such things were left out. But 
UNIX/Linux has grown, and with the advent of multiprocessing rearing its 
head, virtual machines, process migration and such, interest has been 
renewed.

>Try these utilities:
>
>http://mantis.lbl.gov/blcr/doc/html/BLCR_Users_Guide.html
>
>http://www.ncl.cs.columbia.edu/research/migrate/crak.html
>  
>
Interesting.

>JRU
>  
>
JIM

> -------------- Original message ----------------------
>From: "Jason C. Miller" <jason.c.miller at gmail.com>
>  
>
>>My questions are rarely simple...and here's another one.  ;)
>>
>>Does anybody know of a method (or backdoor hack) that would allow a user 
>>to dump the current state of a process and then restore it later?  Kind of  
>>analogous doing a <ctrl>-Z and then an 'fg' later when you want to 
>>unsuspend the proc except, in my instance, the process would be kill()ed 
>>for later resurection.  Kinda like high-level context switch.  
>>
>>If you're still confused as to what I mean, here's the example that 
>>started me wondering...
>>
>>I was using a game emulator that doesn't have a "save/restore game state" 
>>function.  I figured it wouldn't behoove me too terribly much to try to 
>>come up with something on my own.  Say I've been playing for hours and I'm 
>>tired.  I really don't want to use the game's actual "Save" utility 
>>because it might start me at some predetermined checkpoint the next time I 
>>started the game (eg: metroid, zelda).  So, I'd use this magical utility 
>>that I would like to save the current state of the process somewhere on 
>>non-volatile storage.  Later (after so many days and so many reboots), I 
>>restore that process and continue exactly where I left off.  
>>
>>Questions:
>>1. Does UNIX already have a method for doing this that I don't know about?
>>2. My OS fundamentals are rusty.  Any reason why an OS wouldn't be able to 
>>   support this? (waiting for the OS profs out there to chime in on this 
>>   one).  I understand that register values and such would be a problem, 
>>   but if the process was suspended first, would that make a difference?
>>3. Any ideas anyone?
>>
>>                                    -jason
>>
>>
>>
>>
>>-- 
>>
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