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The kdump-tools package provides init scripts and configuration files to
use kdump.
It is as automated as can be at this point, but some manual configuration
may still be required. Specifically:
1. Kernel Configuration
You must boot a kernel that was configured with:
CONFIG_KEXEC=y
CONFIG_CRASH_DUMP=y
For ia64, you also need:
CONFIG_SPARSEMEM=y
For the resulting dump to be useful, you probably also want:
CONFIG_DEBUG_INFO=y
If you use CONFIG_DISCONTIG, then you can only use makedumpfile level
1 (omit zero pages).
2. Kdump Kernel
You must have a kdump kernel, which is either relocatable or built to
start at a non-default address (which you must also set in the kernel
command-line parameter, see below). Linux on ia64 is always
relocatable; recent x86, x86_64, and powerpc kernels have an option
for this:
CONFIG_RELOCATABLE=y
If your architecture does not support this option, you must build it
with a non-default CONFIG_PHYSICAL_START option.
If your boot kernel is relocatable, kdump-config will use it as the
kdump kernel. Otherwise, you will have to provide one. Once you
have a relocatable crash kernel, set KDUMP_KERNEL and if necessary
KDUMP_INITRD in the /etc/default/kdump-tools file.
The kdump kernel needs to be configured with:
CONFIG_CRASH_DUMP=y
3. Kernel Command line parameter
You must boot your kernel with a 'crashkernel=' command line parameter,
for example:
crashkernel=128M
That will reserve 128 MB of memory for the kdump kernel to use in case
of a crash. See Documentation/kdump/kdump.txt in the Linux source for
more advanced crashkernel parameter syntax.
You may also want to add 'nmi_watchdog=1' on certain systems.
4. Local Configuration
The /etc/default/kdump-tools file can be modified to reflect your
setup, if automatic detection fails, or if you need specific
architectural settings.
5. Architectural considerations
A) x86 && PAE && memory > 4 Gigabytes
will need to use KDUMP_KEXEC_ARGS="--elf64-core-headers"
B) x86 and x86_64
Some systems can take advantage of the nmi watchdog. Add
nmi_watchdog=panic to the boot commandline to turn on the watchdog.
The nmi interrupt will call panic if activated.
C) ia64
some systems may need KDUMP_KEXEC_ARGS="--noio". Use this
if the system hangs after a panic, but before the kdump kernel
begins to boot.
6. Magic SysRq key can be used to trigger a crash
You can manually trigger a kernel crash by using the magic SysRq
key. SysRq usage is described in details in the kernel documentation
(https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html)
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