Debugging kernel crashes using kdump
kdump is a service that creates crash dumps when there is a kernel crash. It uses
kexec(8) to boot into a secondary kernel (known as a capture kernel), then exports the contents of the kernel’s memory (known as a crash dump or vmcore) to the filesystem. The contents of vmcore can then be analyzed to root cause the kernel crash.
Configuring kdump requires setting the
crashkernel kernel argument and enabling the kdump systemd service. Memory must be reserved for the crash kernel during booting of the first kernel.
crashkernel=auto generally doesn’t reserve enough memory on Fedora CoreOS, so it is recommended to specify
By default, the vmcore will be saved in
/var/crash. It is also possible to write the dump to some other location on the local system or to send it over the network by editing
/etc/kdump.conf. For additional information, see
kdump.conf(5) and the comments in
- name: kdump.service
Set the crashkernel kernel argument
sudo rpm-ostree kargs --append='crashkernel=300M'
More information on how to modify kargs via
Enable the kdump systemd service.
sudo systemctl enable kdump.service
Reboot your system.
sudo systemctl reboot
It is highly recommended to test the configuration after setting up the
kdump service, with extra attention to the amount of memory reserved for the crash kernel. For information on how to test that kdump is properly armed and how to analyze the dump, refer to the kdump documentation for Fedora and the Linux kernel documentation on kdump.
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