Capturing crash with 4.6.0 and above kernel does not work

[Dave Young]

On 08/25/16 at 05:45pm, Himanshu Madhani wrote:
> 
> 
> On 8/25/16, 1:10 AM, "Michal Hocko" <mhocko at kernel.org> wrote:
> 
> >[Let's add kdump people]
> >
> >On Wed 24-08-16 16:38:56, Himanshu Madhani wrote:
> >> Hello list,
> >> 
> >> I am wondering if anybody has issue capturing crash dump with the 4.6.0 and above kenrel.
> >> 
> >> I have a system, when booted in 4.5.7 kernel is able to capture crash dump.
> >> However, when I boot this system in 4.6.4 and 4.7.2 kernel, crash dump is not 
> >> able to capture any crash. 
> >> 
> >> I am still facing same issue with 4.8.0-rc2+ kernel and from the error at the command prompt, 
> >> it seems like kexec is ignoring “crashkenrel” parameter. 
> >> 
> >> I added below information in https://bugzilla.kernel.org/show_bug.cgi?id=119291. 
> >> 
> >> # uname -r
> >> 4.8.0-rc2+
> >> 
> >> # cat /proc/cmdline 
> >> ro root=/dev/mapper/vg_dut4110-lv_root rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=512M rd_LVM_LV=vg_dut4110/lv_swap rd_LVM_LV=vg_dut4110/lv_root rd_NO_DM rhgb quiet
> >> 
> >> # service kdump status
> >> Kdump is not operational
> >> 
> >> # service kdump start
> >> Memory for crashkernel is not reserved
> >> Please reserve memory by passing "crashkernel=X at Y" parameter to the kernel
> >> Starting kdump:                                            [FAILED]
> >
> >It smells like the crash kernel reservation has failed. Could you
> >provide the full kernel log?
> 
> Attached is kernel log from fresh kernel compile of 4.6.5 (linux-stable) tree

Where is the kernel log?

Seems the kernel log in bugzilla is for crashkernel=128M

Thanks
Dave