Messages in this thread | | | Date | Wed, 27 Sep 2006 14:27:38 +0900 | From | Horms <> | Subject | Re: [Fastboot] Stupid kexec/kdump question... |
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On Tue, Sep 26, 2006 at 10:10:29PM -0700, Andrew Morton wrote: > On Tue, 26 Sep 2006 11:25:06 -0400 > Valdis.Kletnieks@vt.edu wrote: > > > OK, I'm running a Fedora Core 6 (rawhide actually) box with -18-mm1 kernel. > > I've installed kexec-tools and similar, and am trying to get the kernels > > built following the hints in Documentation/kdump/kdump.txt, but a few > > questions arise: > > > > 1) Other than the fact that the Fedora userspace looks for a > > ${kernelvers}kdump kernel, is there any reason the kdump kernel has > > to match the running one, or can an older kernel be used?
The post-crash kernel is not realy dependant on the pre-crash kernel. What is important is that either the kernel is relocatable (which is being worked on for x86 and i386), or it is compiled to run at a non-default address and that address corresponds to the region reserved by the crashkernel command line parameter passed to the pre-crash kernel.
The post-crash kernel will also need CONFIG_CRASH_DUMP and likely CONFIG_PROC_VMCORE
> > 2) I'm presuming that a massively stripped down kernel (no sound support, > > no netfilter, no etc) that just has what's needed to mount the dump location > > is sufficient?
Yes
> > 3) The docs recommend 'crashkernel=64M@16M', but that's 8% of my memory. > > What will happen if I try '16M@16M' instead? Just slower copying due to > > a smaller buffer cache space, or something more evil?
There is a lower bound to how small you can make the space, which is basically how little memory space your post-crash kernel needs. 16M is probably pushing it, but 32M should be more than possible. Experimentation is really the order of the day here.
-- Horms H: http://www.vergenet.net/~horms/ W: http://www.valinux.co.jp/en/
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