Chapter 16. Using early kdump to capture boot time crashes
As a system administrator, you can utilize the
early kdump support of the
kdump service to capture a vmcore file of the crashing kernel during the early stages of the booting process. This section describes what
early kdump is, how to configure it, and how to check the status of this mechanism.
16.1. What is early kdump
Kernel crashes during the booting phase occur when the
kdump service is not yet started, and cannot facilitate capturing and saving the contents of the crashed kernel’s memory. Therefore, the vital information for troubleshooting is lost.
To address this problem, RHEL 8 introduced the
early kdump feature as a part of the
16.2. Enabling early kdump
This section describes how to enable the
early kdump feature to eliminate the risk of losing information about the early boot kernel crashes.
- An active Red Hat Enterprise Linux subscription.
A repository containing the
kexec-toolspackage for your system CPU architecture
kdumpconfiguration and targets requirements.
Verify that the
kdumpservice is enabled and active:
# systemctl is-enabled kdump.service && systemctl is-active kdump.service enabled active
kdumpis not enabled and running, set all required configurations and verify that
kdumpservice is enabled.
initramfsimage of the booting kernel with the
dracut -f --add earlykdump
rd.earlykdumpkernel command line parameter:
grubby --update-kernel=/boot/vmlinuz-$(uname -r) --args="rd.earlykdump"
Reboot the system to reflect the changes
Optionally, verify that
rd.earlykdumpwas successfully added and
early kdumpfeature was enabled:
# cat /proc/cmdline BOOT_IMAGE=(hd0,msdos1)/vmlinuz-4.18.0-187.el8.x86_64 root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet rd.earlykdump # journalctl -x | grep early-kdump Mar 20 15:44:41 redhat dracut-cmdline: early-kdump is enabled. Mar 20 15:44:42 redhat dracut-cmdline: kexec: loaded early-kdump kernel
- What is early kdump support and how do I configure it?
- Enabling and disabling the kdump service