Linux Kernel Crash Book Everything you need to know - Original PDF
نویسندگان: Igor Ljubuncic aka Dedoimedo
خلاصه: www.dedoimedo.com all rights reservedPart IIKdump10 IntroductionLinux kernel is a rather robust entity. It is stable and fault-tolerable and usually does notsuffer irrecoverable errors that crash the entire system and require a reboot to restoreto normal production. Nevertheless, these kinds of problems do occur from time totime. They are known as kernel crashes and are of utmost interest and importance toadministrators in charge of these systems. Being able to detect the crashes, collect themand analyze them provides the system expert with a powerful tool in finding the rootcause to crashes and possibly solving critical bugs.In the previous part (I), we have learned how to setup, configure and use Linux KernelCrash Dump (LKCD) utility. However, LKCD, being an older project, exhibited severalmajor limitations in its functionality: LKCD was unable to save memory dumps to localRAID (md) devices and its network capability was restricted to sending memory coresto dedicated LKCD netdump servers only on the same subnet, provided the cores wereunder 4GB in size. Memory cores exceeding the 32-bit size barrier were corrupt upontransfer and thus unavailable for analysis. The same-subnet also proved impractical forlarge-scale operations with thousands of machines.Kdump is a much more flexible tool, with extended network-aware capabilities. It aimsto replace LKCD, while providing better scalability. Indeed, Kdump supports networkdumping to a range of devices, including local disks, but also NFS areas, CIFS sharesor FTP and SSH servers. This makes if far more attractive for deployment in largeenvironments, without restricting operations to a single server per subnet.In this part of the book, we will learn how to setup and configure Kdump for memorycore dumping to local disks and network shares. We will begin with a short overview ofbasic Kdump functionality and terminology. Next, we will review the kernel compilationparameters required to use Kdump. After that, we will go through the configuration fileand study each directive separately, step by step. We will also edit the GRUB menuas a part of the Kdump setup. Lastly, we will demonstrate the Kdump functionality,including manually triggering kernel crashes and dumping memory cores to local andnetwork devices. In the Appendix section (V), you will also be able to learn aboutchanges and new functionality added in later versions of Kdump, plus specific setups foropenSUSE and CentOS