Date: Wed, 28 Apr 1999 20:03:19 -0700 (PDT) From: papowell@astart4.astart.com To: freebsd-small@FreeBSD.ORG, sverzunov@netscaler.com Subject: Re: Flash based system dump Message-ID: <199904290303.UAA07892@astart4.astart.com>
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> From owner-freebsd-small@FreeBSD.ORG Wed Apr 28 10:39:37 1999 > Date: Wed, 28 Apr 1999 10:31:10 -0700 > From: Sergey Verzunov <sverzunov@netscaler.com> > To: freebsd-small@FreeBSD.ORG > Subject: Flash based system dump > > Hi. > > Is there any method for dumping crashed kernel somewhere, when BSD works > from small (24MB) flash > disk. > Did somebody face with such a problem? > > Thanks a lot. > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-small" in the body of the message > This is usually a nasty problem, solved in different manners on different systems. If a system 'goes down' due to a panic, you can usually generate a core dump in a simple way - 1. Pass 1 - find out how big it is. 2. Pass 2 - write out starting at the top end of memory - 4 bytes 3. Put the length into the last 4 bytes. When you reboot your system, you use /dev/kmem (or whatever it is today) to go to the end of memory, pick up the length, go to where the start looks reasonable, and then copy the file to file. The good news is that if you have LOTS and LOTS of memory, this works fine. The bad news is that some UNIX systems INSIST on using the high memory for a work area, system area, etc. Been there more times than I want to think about. Patrick To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-small" in the body of the message
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