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Chapter 22. Using early kdump to capture boot time crashes

Early kdump captures vmcore files when crashes occur during early boot phases before system services start. It loads the crash kernel and initramfs earlier in memory to preserve troubleshooting information that would otherwise be lost.

22.1. Enabling early kdump
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The early kdump feature sets up the crash kernel and the initial RAM disk image (initramfs) to load early enough to capture the vmcore information for an early crash. This helps to eliminate the risk of losing information about the early boot kernel crashes.

Prerequisites

  • An active Red Hat Enterprise Linux subscription.
  • A repository containing the kexec-tools, kdump-utils, and makedumpfile packages for your system CPU architecture.
  • Fulfilled kdump configuration and targets requirements. For more information see, Supported kdump configurations and targets.

Procedure

  1. Verify that the kdump service is enabled and active: 

    # systemctl is-enabled kdump.service && systemctl is-active kdump.service
enabled
active

    If kdump is not enabled and running, set all required configurations and verify that kdump service is enabled.

  2. Rebuild the initramfs image of the booting kernel with the early kdump functionality: 

    # dracut -f --add earlykdump

  3. Add the rd.earlykdump kernel command line parameter: 

    # grubby --update-kernel=/boot/vmlinuz-$(uname -r) --args="rd.earlykdump"

  4. Reboot the system to reflect the changes: 

    # reboot

Verification

  • Verify that rd.earlykdump is successfully added and early kdump feature is enabled: 

    # cat /proc/cmdline
     
    BOOT_IMAGE=(hd0,msdos1)/vmlinuz-6.12.0-55.9.1.el10_0.x86_64 root=/dev/mapper/rhel-root ro crashkernel=2G-64G:256M,64G-:512M resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet rd.earlykdump
     
    # journalctl -x | grep early-kdump
     
    Sep 13 15:46:11 redhat dracut-cmdline[304]: early-kdump is enabled.
Sep 13 15:46:12 redhat dracut-cmdline[304]: kexec: loaded early-kdump kernel

    See the /usr/share/doc/kdump-utils/early-kdump-howto.txt file for more information.

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