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Chapter 14. Installing kdump

The kdump service is installed and activated by default on the new versions of RHEL 8 installations. With the provided information and procedures, learn what kdump is and how to install if kdump is not enabled by default.

14.1. What is kdump

kdump is a service which provides a crash dumping mechanism and generates a dump file, known as crash dump or a vmcore file. The vmcore file has the contents of the system memory that helps in analysis and troubleshooting. kdump uses the kexec system call to boot into the second kernel, a capture kernel without a reboot and then captures the contents of the crashed kernel’s memory and saves it into a file. The second kernel is available in a reserved part of the system memory.

Important

A kernel crash dump can be the only information available if a system failure occur. Therefore, operational kdump is important in mission-critical environments. Red Hat advises to regularly update and test kexec-tools in your normal kernel update cycle. This is especially important when you install new kernel features.

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 you install kdump, a default /etc/kdump.conf file is created. The /etc/kdump.conf file includes the default minimum kdump configuration, which you can edit to customize the kdump configuration.

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. Under the KDUMP field, enable kdump if not already enabled.

    Enable kdump during RHEL installation
  2. Under Kdump Memory Reservation, select Manual` if you must customize the memory reserve.

  3. Under KDUMP field, in Memory To Be Reserved (MB), set the required memory reserve 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

  • An active RHEL subscription.
  • A repository containing the kexec-tools package for your system CPU architecture.
  • Fulfilled requirements for kdump configurations and targets. For details, see Supported kdump configurations and targets.

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

On kernel-3.10.0-693.el7 onward, the Intel IOMMU driver is supported for kdump. For kernel-3.10.0-514[.XYZ].el7 and early versions, you must ensure that Intel IOMMU is disabled to prevent an unresponsive capture kernel.