KDUMP

Feature that allows the creation of a crashdump whenever the dump of a system's kernel memory needs to be taken; for example when the system panics.

Kdump uses kexec to boot a crash kernel that then has access to the old kernel's memory.

Feature includes:

• kdump-tools
• kexec-tools
• makedumpfile

Debian defaults are ok for most usecases. No custom kernel or initrd are used; the current kernel and initrd are reused as crash kernel / crash initrd.

When using Garden Linux images that support in-place updates, the usi feature is enabled, using this kdump feature as-is is not going to work correctly because of the amount of memory reserved for the dump kernel via the crashkernel kernel parameter.

When using a in-place updates enabled image, because the rootfs of the system is actually a EroFS file packaged into the initrd, the size of the initrd will vary greatly depending on the set of features used to build the image so it's hard to make a recommendation on the amount of memory that should be used for the crashkernel. Also, the initrd gets extracted from the UKI and made available to kdump-tools in /var/lib/kdump.

Enabling kdump on a already installed (already running) system is not supported; or experimentally, the following steps should be taken:

• install kdump-tools and makedumpfile
• copy the initrd to /var/lib/kdump using the name initrd.img-$(uname -r)
• modify the kernel cmdline by modifying /etc/kernel/cmdline either directly of via /etc/kernel/cmdline.d to include crashkernel=XXXM option
• regenerate the boot loader entries
• reboot

References:

https://docs.kernel.org/admin-guide/kdump/kdump.htmlhttps://docs.kernel.org/filesystems/erofs.html