Kexec and Kdump

Contents

• 18.1. Introduction

• 18.2. Required Packages

• 18.3. Kexec Internals

• 18.4. Basic Kexec Usage

• 18.5. How to Configure Kexec for Routine Reboots

• 18.6. Basic Kdump Configuration

• 18.7. Analyzing the Crash Dump

• 18.8. Advanced Kdump Configuration

• 18.9. For More Information

Kexec is a tool to boot to another kernel from the currently running one.  You can perform faster system reboots without any hardware initialization.  You can also prepare the system to boot to another kernel if the system  crashes.

18.1. Introduction¶

With Kexec, you can replace the running kernel with another without a   hard reboot. The tool is useful for several reasons:

• Faster system rebooting

  If, for any reasons, you have to reboot the system frequently, Kexec     can save you significant time.

• Avoiding unreliable firmware and hardware

  Nowadays, computer hardware is complex and serious problems may occur     during the system start-up. You cannot always replace unreliable     hardware immediately. Kexec boots the kernel to a controlled     environment with the hardware already initialized. The risk of     unsuccessful system start is minimized.

• Saving the dump of a crashed kernel

  Kexec preserves the contents of the physical memory. After the     production kernel fails, the capture kernel, which runs in a reserved     memory, saves the state of the failed kernel. The saved image can help     you with the subsequent analysis.

• Booting without GRUB or LILO configuration

  When the system boots a kernel with Kexec, it skips the boot loader     stage. Normal booting procedure can fail due to an error in the boot     loader configuration. With Kexec, you do not depend on a working boot     loader configuration.

18.2. Required Packages¶

If you aim to use Kexec on openSUSE® to speed up reboots or avoid   potential hardware problems, you need to install the   kexec-tools package.

The package kexec-tools contains a script called   kexec-bootloader. It reads the boot loader   configuration and runs Kexec with the same kernel options as the normal   boot loader does. kexec-bootloader -h   gives you the list of possible options.

To set up an environment that helps you obtain useful debug information   in case of a kernel crash, you need to install   makedumpfile in addition.

The preferred method to use Kdump in the SUSE environment is through   the YaST Kdump module. Install the package   yast2-kdump by entering zypper install   yast2-kdump in the command line as root.

Continue?

http://doc.opensuse.org/documentation/html/openSUSE_114/opensuse-tuning/cha.tuning.kexec.html