Oops! Debugging Kernel Panics
A look into what causes kernel panics and some utilities to help gainmore information.
Working in a Linux environment, how often have you seen a kernel panic?When it happens, your system is left in a crippled state untilyou reboot it completely. And, even after you get your system back into afunctional state, you're still left with the question: why? You may have noidea what happened or why it happened. Those questions can be answeredthough,and the following guide will help you root out the cause of some of the conditionsthat led to the original crash.
Figure 1. A Typical Kernel Panic
Let's start by looking at a set of utilities known askexec and kdump. kexec allows you to boot intoanother kernel from an existing (and running) kernel, andkdump is akexec-based crash-dumping mechanism for Linux.
Installing the Required Packages
First and foremost, your kernel should have the following components statically built in to its image:
CONFIG_RELOCATABLE=yCONFIG_KEXEC=yCONFIG_CRASH_DUMP=yCONFIG_DEBUG_INFO=yCONFIG_MAGIC_SYSRQ=yCONFIG_PROC_VMCORE=y
You can find this in /boot/config-`uname -r`.
Make sure that your operating system is up to date with the latest-and-greatest package versions:
$ sudo apt update && sudo apt upgrade
Install the following packages(I'm currently using Debian, but thesame should and will apply to Ubuntu):
$ sudo apt install gcc make binutils linux-headers-`uname -r` ↪kdump-tools crash `uname -r`-dbg
Note: Package names may varyacross distributions.
During the installation, you will be prompted with questions to enablekexec to handle reboots (answer whatever you'd like, but I answered"no"; see Figure 2).
Figure 2.kexec Configuration Menu
And to enable kdump to run and load at system boot, answer"yes" (Figure 3).
Figure 3.kdump Configuration Menu
Configuring kdump
Open the /etc/default/kdump-tools file, and at the very top,you should see the following: