System gets stuck/hung while booting with message "Rebuilding /boot/initrd-xxx-kdump.img"

Solution Verified - Updated -


  • RHEL 5
  • RHEL 6


  • While booting system gets stuck/hung at message "Rebuilding /boot/initrd-xxx-kdump.img"
  • After patching system gets stuck/hung at message "Rebuilding /boot/initrd-xxx-kdump.img" for more than 30 minutes


  • To workaround this behavior boot the system into the older kernel.
  • Turn off the Kdump service at startup. This will allow the system to boot without the kdump service.
# chkconfig kdump off
  • For RHEL6 systems if you are booting with crashkernel=auto replace it with either crashkernel=128M or crashkernel=256M. This is not necessary for RHEL5 systems.
  • After booting up we will have to manually rebuild the kdump initrd.
# touch /etc/kdump.conf
# service kdump start
  • Once the service starts successfully, enable the kdump service back and it is preferred to reboot the system.

  • If the system happens to be a RHEL 5.3 or Rhel 5.3 +, Please check if there are any custom modification on file "/etc/init.d/functions". Because system running on Rhel5.3+ does not populate "/var/log/boot.log" . Please refer the below article for more information.

    How to enable boot-time logging (/var/log/boot.log) in Red Hat Enterprise Linux 5?

Root Cause

  • This behavior can occur if you Install/Update a new kernel or if there are any changes to "kdump.conf" file prior to the reboot.
  • Sometime systems might take a long time to rebuild the initrd image as it depends on the modules which needs to be included and this might be different for each environment.
  • Or it could also be possible that the kdump service is stuck and this needs to be investigated further.
  • So the threshold or waiting time can be around 10 minutes.

Diagnostic Steps

  • One way to check if the system is hung or not is by trying to switch the terminals i.e [Cntrl+Alt+Fn]

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