[Bug 785394] Re: Hard-coded crashkernel=... memory reservation in /etc/grub.d/10_linux is insufficient

[Andy Whitcroft]

It is possible to change the initramfs used for kexec relatively easy,
see kdump.init.d in the source.  We could therefore consider building an
initrd with MODULES=dep, for my machine here that drops the initrd by
10MB compressed and nearly 30MB uncompressed:

  $ zcat /boot/initrd.img-2.6.39-3-generic | wc -c
  36718592
  $ zcat /boot/initrd.img-2.6.39-3-generic.dep | wc -c
  7216640

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https://bugs.launchpad.net/bugs/785394

Title:
  Hard-coded crashkernel=... memory reservation in /etc/grub.d/10_linux
  is insufficient

Status in “grub2” package in Ubuntu:
  New
Status in “kexec-tools” package in Ubuntu:
  In Progress

Bug description:
  Binary package hint: grub-pc

  This concerns grub-pc 1.99~rc1-13ubuntu3 in Ubuntu Natty.

  The /etc/grub.d/10_linux file contains this snippet:

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

  I am on a system with 2GB of RAM (reported as 2038MB), and according
  to the kernel startup messages, 64MB is reserved for the crash kernel.

  Unfortunately, this does not appear to be enough memory for the
  regular Ubuntu kernel to boot. I am attaching a kernel log obtained
  via serial cable; it shows the initial boot, a crash in the kernel's
  video-driver-related code, the subsequent crashkernel boot, and then
  an apparent "out of memory" kernel panic. (A side effect of the
  "double crash" is that the system is left unresponsive, requiring a
  manual reset instead of rebooting itself automatically.)

  If I double the memory numbers in the crashkernel=... argument, so
  that the reservation is 128MB, the system correctly goes on to attempt
  a vmcore dump and reboot.