Kdump, A Kexec-based Kernel Crash Dumping Mechanism Vivek Goyal Eric W. Biederman Hariprasad Nellitheertha IBM Linux NetworkX IBM
[email protected] [email protected] [email protected] Abstract important consideration for the success of a so- lution has been the reliability and ease of use. Kdump is a crash dumping solution that pro- Kdump is a kexec based kernel crash dump- vides a very reliable dump generation and cap- ing mechanism, which is being perceived as turing mechanism [01]. It is simple, easy to a reliable crash dumping solution for Linux R . configure and provides a great deal of flexibility This paper begins with brief description of what in terms of dump device selection, dump saving kexec is and what it can do in general case, and mechanism, and plugging-in filtering mecha- then details how kexec has been modified to nism. boot a new kernel even in a system crash event. The idea of kdump has been around for Kexec enables booting into a new kernel while quite some time now, and initial patches for preserving the memory contents in a crash sce- kdump implementation were posted to the nario, and kdump uses this feature to capture Linux kernel mailing list last year [03]. Since the kernel crash dump. Physical memory lay- then, kdump has undergone significant design out and processor state are encoded in ELF core changes to ensure improved reliability, en- format, and these headers are stored in a re- hanced ease of use and cleaner interfaces. This served section of memory. Upon a crash, new paper starts with an overview of the kdump de- kernel boots up from reserved memory and pro- sign and development history.