3.15. Configuring kdump for Microsoft Azure instances

Procedure

1. Install kdump and other necessary packages:

   # dnf install kexec-tools kdump-utils makedumpfile

2. Verify that the default location for crash dump files is set in the kdump configuration file and that the /var/crash file is available:

   # grep -v "#" /etc/kdump.conf
   
   path /var/crash
   core_collector makedumpfile -l --message-level 7 -d 31

3. Based on the RHEL VM size and version, check if you need a vmcore target with more free space, such as /mnt/crash:

   Expand

   表 3.3. Virtual machine sizes that have been tested with GEN2 VM on Azure

   RHEL Version	Standard DS1 v2 (1 vCPU, 3.5GiB)	Standard NV16as v4 (16 vCPUs, 56 GiB)	Standard M416-208s v2 (208 vCPUs, 5700 GiB)	Standard M416ms v2 (416 vCPUs, 11400 GiB)
   RHEL 9.4 - RHEL 10	Default	Default	Target	Target

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   • Default indicates that kdump works as expected with the default memory and the default kdump target. The default kdump target is the /var/crash file.
   • Target indicates that kdump works as expected with the default memory. However, you might need to assign a target with more free space.

4. To assign a target with free space, such as /mnt/crash, edit the /etc/kdump.conf file and replace the default path:

   $ sed s/"path /var/crash"/"path /mnt/crash"

   The option path /mnt/crash represents the path to the file system where kdump saves the crash dump file.

   For details, such as writing the crash dump file to a different partition, directly to a device or storing it to a remote machine, see Configuring the kdump target.

5. Increase the crash kernel size to the sufficient size for kdump to capture the vmcore by adding the relative boot parameter if the instance required:

   For example, for a Standard M416-208s v2 VM, the sufficient size is 512 MB, so the boot parameter would be crashkernel=512M.

   1. Open the GRUB configuration file and add crashkernel=512M to the boot parameter line:

      # vi /etc/default/grub
      
      GRUB_CMDLINE_LINUX="console=tty1 console=ttyS0 earlyprintk=ttyS0 rootdelay=300 crashkernel=512M"

   2. Update the GRUB configuration file:

      # grub2-mkconfig -o /boot/grub2/grub.cfg --update-bls-cmdline

6. Reboot the VM to allocate separate kernel crash memory to the VM.