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What's current best practice to capture full kernel stack traces on a Linux system (RHEL 5.x, kernel 2.6.18) that occasionally panics in a device driver?

I'm used to the "old" SunOS way of doing things - crash dumps get written to swap, and on reboot the dump gets retrieved in the local file system. man 8 crash refers to diskdump, but that appears to be unsupported. and/or deprecated.

I've played with kdump, but it's unclear whether I can get a stack trace from that. Triggering a panic via Magic SysRq didn't create one. It also seems wasteful to reserve so much memory (128MB) just for a kexec crash recovery kernel.

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The last time I did any of this (2.6.18 era, actually) I used a serial-console configuration to get crash-dump data. That's useless in a VM context these days as nearly every VM system doesn't so serial. No idea if that's latest, though. – sysadmin1138 Sep 15 '10 at 20:06
@sysadmin1138: both VirtualBox and QEMU KVM have support for serial ports. – Cristian Ciupitu Sep 15 '10 at 20:39
@cristian Hooray! VMWare doesn't, and that's what I have in front of me. – sysadmin1138 Sep 15 '10 at 21:31
@sysadmin1138: well, at least VMWare 3.2 had support for serial ports :-) – Cristian Ciupitu Sep 15 '10 at 22:04
@sysadmin1138: Funny, I'm trying to think of a VM solution that doesn't do serial. And wondering why you would use such a solution. – Matthew Iselin Sep 15 '10 at 23:56

If you are looking to log output in case of a kernel panic with Linux, kdump is the way to go. This is what Red Hat trains people to use and what I have known to be the standard approach.

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Maybe the stack trace makes it through a netconsole (/usr/src/linux/Documentation/networking/netconsole.txt). Worth a try, since it's almost no effort.

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netconsole.txt link for the lazy ones. – Cristian Ciupitu Sep 16 '10 at 0:36
Thanks. SO should link stuff like that automatically ;-) – al. Sep 16 '10 at 12:22

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