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From: pcg@aber-cs.UUCP (Piercarlo Grandi)
Newsgroups: comp.unix.wizards
Subject: Re: "Check pointing" on BSD Unix (or Ultrix)
Summary: Checkpoint: undump, or an Olivetti work...
Keywords: gcore checkpoint dbx
Message-ID: <1487@aber-cs.UUCP>
Date: 10 Nov 89 19:42:43 GMT
Reply-To: pcg@cs.aber.ac.uk (Piercarlo Grandi)
Organization: Dept of CS, UCW Aberystwyth
	(Disclaimer: my statements are purely personal)
Lines: 33

In article <1326@utkcs2.cs.utk.edu> battle@alphard.cs.utk.edu (David Battle) writes:
    Does anyone out there know of any way to "check point" a process
    under BSD unix?  In particular I am interested in a way to do it on
    a Ultrix VAX and possibly on a DECStation 3100.
    
    What I would like to be able to do would be to stop a running process,
    save it's core image to a file (similar to what gcore(1) does), kill
    the original process, and then later (like, say, after rebooting)
    restart the process from the saved core image.

You have two choices; one is the famous undump program, that comes with TeX,
that is used to produces restartable, loaded images for programs that take a
long time to initialize. What you get with undump is the ability to restart
a program with memory as it was when it was stopped. Every other resource
must be reinitialized by the program itself (e.g., files must be reopened and
repositioned, etc...).

A more complete approach is described in some EUUG Bulletin, has been done
by people at Olivetti (?), and is a virtually full checkpoint/restart
facility.

If you want more information, I can dig up the exact reference, but I am
pretty sure it is not a product, just a demonstration of concept, and you
will have some difficulty laying your hands on it.

A full checkpoint restart facility is difficult to do under Unix, because a
process has a lot of relationships to other entities, and checkpointing them
all is hard, not to speak of restarting them (from open files to pipes to
socket connections, child process, etc...).
-- 
Piercarlo "Peter" Grandi           | ARPA: pcg%cs.aber.ac.uk@nsfnet-relay.ac.uk
Dept of CS, UCW Aberystwyth        | UUCP: ...!mcvax!ukc!aber-cs!pcg
Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk