How is kdump able to capture a crash dump?
In order for kdump to be able to capture a kernel crash dump and save it for further analysis, a part of the system memory has to be permanently reserved for the capture kernel. When reserved, this part of the system memory is not available to main kernel.
Where can I find kernel crash dump data?
Crash dump data can be obtained from the context of a newly started kernel, rather than from the context of an already crashed kernel. Lkcd (Linux kernel crash dump), netdump and diskdump have been included in LDPs (Linux documen station project) kernel.
How does kdump boot into a second kernel?
The crash dumps are captured from the context of a freshly booted kernel; not from the context of the crashed kernel. Kdump uses kexec to boot into a second kernel whenever the system crashes.
How to enable or disable kdump in Linux?
To enable Kdump by using the Kernel Dump Configuration GUI. Enter the following command. The Kernel Dump Configuration GUI starts. If Kdump is currently disabled, the green Enable button is selectable and the Disable button is greyed out. Click Enable to enable Kdump.
How to enable multiple CPUs in kdump kernel?
With CONFIG_SMP=y, usually nr_cpus=1 need specified on the kernel command line when loading the dump-capture kernel because one CPU is enough for kdump kernel to dump vmcore on most of systems. However, you can also specify nr_cpus=X to enable multiple processors in kdump kernel.
How to dump vmcore in kdump by default?
(CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.) On i386, enable high memory support under “Processor type and features”: With CONFIG_SMP=y, usually nr_cpus=1 need specified on the kernel command line when loading the dump-capture kernel because one CPU is enough for kdump kernel to dump vmcore on most of systems.
Can a kdump dump be read with Elf?
By default, makedumpfile makes a DUMPFILE in the kdump-compressed format. The kdump-compressed format can be read only with the crash utility, and it can be smaller than the ELF format because of the compression support.