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Kdump is a tool used for capturing and analyzing kernel dumps, which proves invaluable in diagnosing the causes of system crashes, commonly known as kernel panics. Employing Kdump on a CentOS 7 system requires several steps to properly configure and utilize it. This article provides a detailed, step-by-step guide on how to configure Kdump and subsequently analyze its outputs to uncover the root causes of issues.

Prerequisites Before installing and configuring Kdump, ensure you have:

• Adequate disk space for storing dumps.
• Administrator (root) privileges to make changes and install packages.

Installing Kdump

1. Package Installation: The first step involves installing Kdump and related tools. This can be achieved using the yum command:

   yum install kexec-tools crash kernel-devel
   ​

2. Enabling Kdump Service: After installation, enable and start the Kdump service using systemctl:

   systemctl enable kdump.service
   systemctl start kdump.service
   ​

Configuring Kdump

1. Editing Configuration File: To configure Kdump, you need to edit the /etc/kdump.conf file. This file specifies where the dump will be saved and how large it should be.
2. Dump Storage: You can specify the target location for the dump (local disk, network storage, etc.). Example configuration for storing on a local disk:

   path /var/crash
   ​

3. Dump Size: In the configuration file, you can also limit the dump size using the core_collector makedumpfile directive. For instance, to reduce the dump size by skipping free memory and cache:

   core_collector makedumpfile -c --message-level 1 -d 31
   ​

Testing Kdump To verify that Kdump is correctly configured and functioning, you can induce an artificial kernel panic. Note that this should only be done on a test system:

echo c > /proc/sysrq-trigger

This command triggers a kernel panic and initiates Kdump to capture the kernel dump.

Analyzing the Dump After rebooting the system, you can find dump files in the configured location (/var/crash). To analyze these dumps, you can use the crash tool. The crash tool can be invoked with the path to the kernel dump and the corresponding system map file, for example:

crash /usr/lib/debug/lib/modules/$(uname -r)/vmlinux /var/crash/2021-01-01-01:01/vmcore

Utilizing Kdump for analyzing kernel panics and system crashes on CentOS 7 is an effective way to identify and address issues related to the operating system kernel. Proper configuration and utilization of this tool can significantly simplify the diagnostic process and enhance the stability and security of the system.