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Chapter 12. Installing kdump
kdump service is installed and activated by default on the new Red Hat Enterprise Linux installations. The following sections explain what
kdump is and how to install
kdump when it is not enabled by default.
12.1. 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.
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.
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.
12.2. 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.
Go to the
kdumpif not already enabled.
Define how much memory should be reserved for
12.3. 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.
- An active RHEL subscription
- The kexec-tools package
Fulfilled requirements for
kdumpconfigurations and targets. For details, see Supported kdump configurations and targets.
kdumpis installed on your system:
# rpm -q kexec-tools
Output if the package is installed:
Output if the package is not installed:
package kexec-tools is not installed
kdumpand other necessary packages by:
# dnf install kexec-tools
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.