How to Troubleshoot Linux Kernel Panics?
Problem Description:
Kernel panics on Linux are hard to identify and troubleshoot. Troubleshooting kernel panics often requires reproducing a situation that occurs rarely and collecting data that is difficult to gather.
Solution Summary:
This document outlines several techniques that will help reduce the amount of time necessary to troubleshoot a kernel panic.
Technical Discussion:
What is a kernel panic?
As the name implies, the Linux kernel gets into a situation where it doesn’t know what to do next. When this happens, the kernel gives as much information as it can about what caused the problem, depending on what caused the panic.
There are two main kinds of kernel panics:
- Hard Panic – also known as Aieee!
- Soft Panic – also known as Oops
What can cause a kernel panic?
Only modules that are located within kernel space can directly cause the kernel to panic. To see what modules are dynamically loaded, do lsmod – this shows all dynamically loaded modules (Dialogic drivers, LiS, SCSI driver, filesystem, etc.). In addition to these dynamically loaded modules, components that are built into the kernel (memory map, etc.) can cause a panic.
Since hard panics and soft panics are different in nature, we will discuss how to deal with each separately.
How to Troubleshoot a Hard Kernel Panic
Hard Panics – Symptoms:
- Machine is completely locked up and unusable.
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