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[Cs-gon <1555103@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

To debug kernel crashes, I have installed and configured the kernel
crash dumps on a 14.04 system (with Wily HWE Stack, but the problem
exist with older an newer kernels too).

I have used the following documentation:

https://wiki.ubuntu.com/Kernel/CrashdumpRecipe
https://help.ubuntu.com/lts/serverguide/kernel-crash-dump.html

The default kernel option is:

crashkernel=384M-:128M

The output of kdump-config show:

# kdump-config show
USE_KDUMP:        1
KDUMP_SYSCTL:     kernel.panic_on_oops=1
KDUMP_COREDIR:    /var/crash
crashkernel addr: 0x24000000
current state:    ready to kdump

kexec command:
  /sbin/kexec -p --command-line="BOOT_IMAGE=/vmlinuz-4.2.0-30-generic root=/dev/mapper/VolGroup00-rootlv ro quiet splash vt.handoff=7 irqpoll maxcpus=1 nousb" --initrd=/boot/initrd.img-4.2.0-30-generic /boot/vmlinuz-4.2.0-30-generic


When using the "echo c > /proc/sysrq-trigger" to induce a crash, nothing happens after the Oops gets printed on the console. I have to manually turn the system off an on again, and of course, no crash dump is found in /var/crash.


After raising the reserved memory to 256MB (crashkernel=384M-:256M), and triggering the crash using the sysrq, the new kernel gets started shortly after the Oops,  and after the following reboot the crash dump is in /var/crash, as expected.

The system is a Lenovo T450s with amd64 installation.

** Affects: kexec-tools (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1555103

Title:
  kdump: does not generate a dump on 14.04, because the reserved memory
  is too low

Status in kexec-tools package in Ubuntu:
  New

Bug description:
  To debug kernel crashes, I have installed and configured the kernel
  crash dumps on a 14.04 system (with Wily HWE Stack, but the problem
  exist with older an newer kernels too).

  I have used the following documentation:

  https://wiki.ubuntu.com/Kernel/CrashdumpRecipe
  https://help.ubuntu.com/lts/serverguide/kernel-crash-dump.html

  The default kernel option is:

  crashkernel=384M-:128M

  The output of kdump-config show:

  # kdump-config show
  USE_KDUMP:        1
  KDUMP_SYSCTL:     kernel.panic_on_oops=1
  KDUMP_COREDIR:    /var/crash
  crashkernel addr: 0x24000000
  current state:    ready to kdump

  kexec command:
    /sbin/kexec -p --command-line="BOOT_IMAGE=/vmlinuz-4.2.0-30-generic root=/dev/mapper/VolGroup00-rootlv ro quiet splash vt.handoff=7 irqpoll maxcpus=1 nousb" --initrd=/boot/initrd.img-4.2.0-30-generic /boot/vmlinuz-4.2.0-30-generic

  
  When using the "echo c > /proc/sysrq-trigger" to induce a crash, nothing happens after the Oops gets printed on the console. I have to manually turn the system off an on again, and of course, no crash dump is found in /var/crash.

  
  After raising the reserved memory to 256MB (crashkernel=384M-:256M), and triggering the crash using the sysrq, the new kernel gets started shortly after the Oops,  and after the following reboot the crash dump is in /var/crash, as expected.

  The system is a Lenovo T450s with amd64 installation.

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