[Bug 1206691] Re: crashkernel setting rarely works on a system with little memory

[David Medberry]

Hi Louis,

Thanks for the response (and I fully agree and went ahead after I was
convinced.)

My official writeup settled it this way (which works for even the smallest
instance on Azure):

WAS:
  74 # add crashkernel option if we have the required tools
    75 if [ -x "/usr/bin/makedumpfile" ] && [ -x "/sbin/kexec" ]; then
    76     GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA
crashkernel=384M-2G:64M,2G-:128M"

IS:
    74 # add crashkernel option if we have the required tools
    75 if [ -x "/usr/bin/makedumpfile" ] && [ -x "/sbin/kexec" ]; then
    76     GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA
crashkernel=384M-700M:64M,700M-:128M"

The smallest image on Azure is 768M.


On Wed, Aug 14, 2013 at 4:18 AM, Louis Bouchard <
louis.bouchard at canonical.com> wrote:

> AFAIK, this bug may be a duplicate of the following longstanding bug :
>
> https://bugs.launchpad.net/ubuntu/+source/kexec-tools/+bug/785394
>
> I have made a habit of increasing the reserved crashkernel= value to
> 128Mb which is the default in debian though I understand that it may be
> costly on micro instances
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1206691
>
> Title:
>   crashkernel setting rarely works on a system with little memory
>
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-- 
-dave

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https://bugs.launchpad.net/bugs/1206691

Title:
  crashkernel setting rarely works on a system with little memory

Status in “grub2” package in Ubuntu:
  Incomplete

Bug description:
  In the file /etc/grub.d/10_linux

  you will find:

      87	# add crashkernel option if we have the required tools
      88	if [ -x "/usr/bin/makedumpfile" ] && [ -x "/sbin/kexec" ]; then
      89	    GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA crashkernel=384M-2G:64M,2G-:128M"
      90	fi

  However, I've not seen the 384M-2G:64M work since precise. It works
  fine if you bump it up to 128M (or just make it crashkernel=128M)

  It's not clear to me where to make this change:
  medberry at handsofblue:~/work/grub2/grub2$ find . -name 10_linux\* -print0 |xargs --null grep crashkernel
  ./.pc/ubuntu_failed_boot_menu.patch/util/grub.d/10_linux.in:# add crashkernel option if we have the required tools
  ./.pc/ubuntu_failed_boot_menu.patch/util/grub.d/10_linux.in:    GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA crashkernel=384M-2G:64M,2G-:128M"
  ./.pc/ubuntu_gfxpayload_filter.patch/util/grub.d/10_linux.in:# add crashkernel option if we have the required tools
  ./.pc/ubuntu_gfxpayload_filter.patch/util/grub.d/10_linux.in:    GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA crashkernel=384M-2G:64M,2G-:128M"
  ./.pc/ubuntu_linux_quiet.patch/util/grub.d/10_linux.in:# add crashkernel option if we have the required tools
  ./.pc/ubuntu_linux_quiet.patch/util/grub.d/10_linux.in:    GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA crashkernel=384M-2G:64M,2G-:128M"
  ./.pc/ubuntu_recovery_nomodeset.patch/util/grub.d/10_linux.in:# add crashkernel option if we have the required tools
  ./.pc/ubuntu_recovery_nomodeset.patch/util/grub.d/10_linux.in:    GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA crashkernel=384M-2G:64M,2G-:128M"
  ./.pc/ubuntu_vt_handoff.patch/util/grub.d/10_linux.in:# add crashkernel option if we have the required tools
  ./.pc/ubuntu_vt_handoff.patch/util/grub.d/10_linux.in:    GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA crashkernel=384M-2G:64M,2G-:128M"
  ./util/grub.d/10_linux.in:# add crashkernel option if we have the required tools
  ./util/grub.d/10_linux.in:    GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA crashkernel=384M-2G:64M,2G-:128M"

  as it appears so many times but the likeliest place is a new patch
  somewhere. Alternatively, having a way to modify this via something
  akin to grub.d/42_custom may work.

  (This may be considered a Denial of Service as a crash won't work
  without enough memory and may hang booting--but crashing in the first
  place is already a limited DoS....)

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