Just to be clear, is the dependency on kexec only to install kexec-tools?
In other words, the systemd setup on the kexec page is for example for quick reboot, but is not needed for kdump to work. If one wants to just do kdump one may skip the kexec systemd stuff - do I have that right? SanjeevKSharma (talk) 17:20, 27 October 2013 (UTC)
how are others setting up automatic crash dump (no user intervention) then reboot?
For cases where the video is messed up it would be great to just dump the crashed kernel and hard reboot with no keyboard or terminal interaction. So if kexec, kdump and systemd are all working but video/console corruption is hiding it one still gets a dump file.
here are 2 setups that are doing it but they don't specify how exactly - maybe setting off a shell script from the boot parameters in grub or syslinux?
Intel iommu can cause problems
when I manually crashed the machine it just sat there for 5 minutes. Second time I tried I took a shower & when I came back the stack trace screen was still there. I found reports of Intel iommu  causing issues on one of Redhat's kdump pages and a kernel mailing list
I added " intel_iommu=off" to "--append="root=/dev/s..." in kdump.service
 the reports have it as only affecting intel, not AMD iommu.
No crash dump showing up
I manually panic my machine - the stack trace screen shows up then the new kernel comes up ... and there's no /proc/vmcore
I grep'd the kernel source tree I compiled from
grep -r CONFIG_CRASH_ *
CONFIG_DEBUG_INFO is in there too so I assume the kernel built with those CONFIG_ options.
update: I had placed the echoing of the 3 kernel config options close to the bottom of the build() in PKGCONFIG; the options didn't take effect. place that echo @ or near the top of the build. There's a tool, extract-ikconfig, in the kernel source that shows the options - run it against the compiled image or the installed, compressed image
/usr/src/linux-3.11.5-1-ARCH/scripts/extract-ikconfig /home/sam/BAK/KERNEL/core/linux/src/linux-3.11/vmlinux /usr/src/linux-3.11.5-1-ARCH/scripts/extract-ikconfig /boot/vmlinuz-linux-withKDUMP SanjeevKSharma (talk) 00:07, 29 October 2013 (UTC)
And there's file /proc/config.gz, which is just the config file all by itself for the currently running kernel.