Red Hat Training

A Red Hat training course is available for RHEL 8

Chapter 14. Installing kdump

The kdump service is installed and activated by default on the new Red Hat Enterprise Linux installations. Learn about kdump and how to install kdump when it is not enabled by default.

14.1. What is kdump

kdump is a service which provides a crash dumping mechanism. The service enables you to save the contents of the system memory for analysis. kdump uses the kexec system call to boot into the second kernel (a capture kernel) without rebooting; and then captures the contents of the crashed kernel’s memory (a crash dump or a vmcore) and saves it into a file. The second kernel resides in a reserved part of the system memory.

Important

A kernel crash dump can be the only information available in the event of a system failure (a critical bug). Therefore, operational kdump is important in mission-critical environments. Red Hat advise that system administrators regularly update and test kexec-tools in your normal kernel update cycle. This is especially important when new kernel features are implemented.

You can enable kdump for all installed kernels on a machine or only for specified kernels. This is useful when there are multiple kernels used on a machine, some of which are stable enough that there is no concern that they could crash.

When kdump is installed, a default /etc/kdump.conf file is created. The file includes the default minimum kdump configuration. You can edit this file to customize the kdump configuration, but it is not required.

14.2. Installing kdump using Anaconda

The Anaconda installer provides a graphical interface screen for kdump configuration during an interactive installation. The installer screen is titled as KDUMP and is available from the main Installation Summary screen. You can enable kdump and reserve the required amount of memory.

Procedure

  1. Go to the Kdump field.

  2. Enable kdump if not already enabled.

    Enable kdump during RHEL installation

  3. Define how much memory should be reserved for kdump.

    Kdump Memory Reservation

14.3. Installing kdump on the command line

Some installation options, such as custom Kickstart installations, in some cases do not install or enable kdump by default. If this is your case, follow the procedure below.

Prerequisites

Procedure

  1. Check whether kdump is installed on your system: 

    # rpm -q kexec-tools

    Output if the package is installed: 

    kexec-tools-2.0.17-11.el8.x86_64

    Output if the package is not installed: 

    package kexec-tools is not installed

  2. Install kdump and other necessary packages by: 

    # dnf install kexec-tools
Important

Starting with kernel-3.10.0-693.el7 the Intel IOMMU driver is supported with kdump. For prior versions, kernel-3.10.0-514[.XYZ].el7 and earlier, it is advised that Intel IOMMU support is disabled, otherwise the capture kernel is likely to become unresponsive.