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Linux Kernel Crashdumps: HOW?

... and links to lots of unofficial kernel patches

From Sachin

Answered By Jim Dennis

Hi All,

How do we configure dump device on linux( SuSE 7.1 ) so that when system panics I can get kernel crash dump.I have two scsi disks and want to use one of the scsi disk as dump device.

Thanks,
Sachin

[JimD] Linux doesn't crash. (Well, not very often, anyway).

More to the point, the canonical Linux kernel doesn't include "crashdump" support (where a kernel panic dumps the system core state to the swap partitions or some other device). Linus doesn't consider this to be a sufficiently compelling feature to offset the increased code complexity that it entails. (Linux also doesn't panic as easily as some other UNIX kernels --- it will log an "Oops" for those hardware errors or device driver bugs that are considered "recoverable").

However, if you really want this feature, you can apply the "lkcd" (Linux Kernel Crash Dump) kernel patches from SGI's OSS (Open Source Software) web site at:

http://oss.sgi.com/projects/lkcd

You'll also want to grab the suite of utilities that goes with the kernel patch. The vmdump command configures the kernel to use its dump feature (telling it which swap partition to use for example) and another vmdump directive is normally used to detect and save dumps. (If your familiar with the 'savecore' command in some other forms of UNIX, then this will make sense to you).

There's also an 'lcrash' utility which is used to help perform crashdump analysis.

Note that there are a number of other "unofficial" kernel patches like this one. For example there are interactive kernel debuggers that you can compile into your system's kernel.

You can read about some of them at:

http://oss.sgi.com/projects

... and find more at:

Rock Projects Collection (takes over where Linux Mama left off)

http://linux-patches.rock-projects.com

LinuxHQ http://www.linuxhq.com/kernel (Look for the links like "Unofficial kernel patches").

IBM ("Big Blue")

http://oss.software.ibm.com/developer/opensource/linux/patches/kernel.php

(Mostly small, deep performance tweaks and bugfixes, and simple feature enhancements).

Ibiblio (formerly Metalab, formerly Sunsite.unc.edu) http://www.ibiblio.org/pub/Linux/kernel/patches!INDEX.html (Mostly very old).

Adrea Arcangeli (et al)'s In Kernel Debugger:

ftp://e-mind.com/pub/andrea/ikd

The International/Crypto Support Patch

http://www.kerneli.org

FreeS/WAN IPSec (includes some patches which aren't at kerneli)

http://www.freeswan.org

Solar Designer's Security Features Patches

http://www.openwall.com/linux

... and some additions to that from "Hank":

http://www.doutlets.com/downloadables/hap.phtml

... and the "Linux Intrusion Defense/Detection System"

http://www.lids.org

(which mostly incorporates and builds upon the Openwall patches and lots more)

U.S. National Security Agency's "Security Enhanced" Linux

http://www.nsa.gov/selinux/download.html

(Yes, you read that right! The secretive "no such agency" has released a set of open source Linux patches. Everybody's getting into the Linux kernel security patch game!)

... and even more

http://www1.informatik.uni-erlangen.de/tree/Persons/bauer/new/linux-patches.html

(Links with some duplicates to the list I've created here).

I've deliberately left out all of the links to "real-time" kernel patches. (I think I created a link list for an answer that related to various forms of "real-time" Linux (RTLinux, RTAI, KURT, TimeSys.com et al) within the last couple of months. (Search the back issues for it, if you need more on that).

So, obviously there are alot of unofficial kernel patches out there.

One reason I went to the bother of list all these sites, is that I'm guessing that you might be doing kernel development work. Linux kernels just don't crash very often in production use so that seems like the mostly likely reason for anyone to need crash dump support. (Besides, it'll amuse the rest of my readership).

Among these many patches you may find good examples and useful code that you can incorporate into your work.

This page edited and maintained by the Editors of Linux Gazette Copyright © 2001
Published in issue 67 of Linux Gazette June 2001

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