Kdump (Linux)

kdump is a feature of the Linux kernel that creates crash dumps in the event of a kernel crash. When triggered, kdump exports a memory image (also known as vmcore) that can be analyzed for the purposes of debugging and determining the cause of a crash. The dumped image of main memory, exported as an Executable and Linkable Format (ELF) object, can be accessed either directly through /proc/vmcore during the handling of a kernel crash, or it can be automatically saved to a locally accessible file system, to a raw device, or to a remote system accessible over network.

In the event of a kernel crash, kdump preserves system consistency by booting another Linux kernel, which is known as the dump-capture kernel, and using it to export and save a memory dump. As a result, the system boots into a clean and reliable environment instead of relying on an already crashed kernel that may cause various issues, such as causing file system corruption while writing a memory dump file. To implement this "dual kernel" layout, kdump uses kexec for booting into the dump-capture kernel immediately after the kernel crash, using kexec's ability to boot "over" the currently running kernel while avoiding the execution of a bootloader and hardware initialization performed by the system firmware (BIOS or UEFI). A dump-capture kernel can be either a separate Linux kernel image built specifically for that purpose, or the primary kernel image can be reused on architectures that support relocatable kernels.

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