This article describes how to generate a crashdump from an unresponsive XenServer 7.

If XenServer crashes, the running kernel can migrate into a special memory area which is based on kexec functions that loads a special kernel without the need for a server cold restart. This new kernel attempts to gather as much details about the crash as possible (memory dumps, process list) and save it into the /var/crash directory.

In some instances, XenServer hangs and does not reboot after a crash. In this situation, the server is unresponsive but still running and only a reboot of the server can resolve the issue. This could cause a situation where no crashdumps are available on the server, that is, no dump in the /var/crash directory and the xe host-crashdump-list contains no information about the crash.

In this situation, you can force a crashdump that saves information about the crash which can then be analyzed.

Requirements

• Citrix XenServer 7 or later.
• Serial console access (real or emulated)

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Instructions

To generate a crashdump file from an unresponsive XenServer 7 or later version, complete the following procedure:

1. If you are not using COM1 on your server, edit /etc/grub.cfg file as follows:

• Locate the append line below label 'XenServer (Serial)'.

  menuentry 'XenServer (Serial)' {
          search --label --set root root-qeexyy
          multiboot2 /boot/xen.gz com1=115200,8n1 console=com1,vga dom0_mem=2048M,max:2048M watchdog ucode=scan dom0_max_vcpus=8 crashkernel=128M@256M
          module2 /boot/vmlinuz-4.4-xen root=LABEL=root-qeexyy ro nolvm hpet=disable console=tty0 xencons=hvc console=hvc0
          module2 /boot/initrd-4.4-xen.img
  }

• Edit the values of com1 and com<n>, where <n> represents your COM port number.

2. Reboot the XenServer host.
3. From the menu, select XenServer (Serial) and press Enter. 4. XenServer starts with serial console support and customers can connect Microsoft's HyperTerminal (or a similar terminal emulator) to the serial console.
5. Press Ctrl + A thrice. 6. Press h to display all available operation to check if the configuration is valid.
7. Wait until XenServer hangs.
8. Repeat step 5 through 6, then press Shift + C (capital C character) to trigger a crashdump. 9. Wait until XenServer reboots itself and save all data on a local file system.
10. Check for the new crash dump on the server: