In this tutorial i will show you how to install and setup the KDUMP in Redhat 7 / CentOS 7 for analysis KDUMP is a kernel crash dump m...
In this tutorial i will show you how to install and setup the KDUMP in Redhat 7 / CentOS 7 for analysis
KDUMP is a kernel crash dump mechanism that is used to capture the crash dumps when the system crashes.
If a system crashes with kdump enabled , kdump will invoke kexec to boot into second kernel,This second kernel resides in reserved part of the system memory and it is inaccessible to the first kernel
The second kernel main job is to capture the crash dump whenever the system crashes and these logs will be for finding the root cause why the system crashes.
Installation steps:
Step 1: Install the Kexec toolsyum -y install kexec-toolsStep 2: Configure the memory for kdump
To do this we need to edit the grub configuration file /etc/default/grub as root and search for the word GRUB_CMDLINE_LINUX and replace the "auto" option with the amount of memory you want to reserve
Step 3: Regenerate the Grub2 configuration
For BIOS firmware use the below command
grub2-mkconfig -o /boot/grub2/grub.cfgFor UEFI firmware use the below command
grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfgStep 4:Configure the Dump location
If your system crashes, the core dump will be stored in the default location /var/cores, if you want to change you can edit the /etc/kdump.conf file as root and provide the required destination in the path location path /usr/local/cores or you can provide the raw device or nfs location also.
eg: raw /dev/sdc1
Step 5 : Configure the core compression and action
To enable the compression edit the file /etc/kdump.conf as root and look for the core_collector makedumpfile -l --message-level 1 -d 31 and change it to core_collector makedumpfile -c
where -c for compress
For changing the action search for the word default shell and change it to default reboot
Step 6 : Enabling the service
Start the service and also at boot time
systemctl start kdump.service
systemctl enable kdump.service
Check the service is active or dead and then proceed for crashing, if it is dead start and provide the below commands
echo 1 > /proc/sys/kernel/sysrq
echo c > /proc/sysrq-triggerThe above commands will crash the system immediately and after reboot , the dump file will be available under the location mentioned in kdump.conf
Step 8 : Install the crash
To know the exact root cause for the crash we need to analze the crash , for that crash and kernel-debuginfo package need to be installed and for debuginfo package we need to enable the repo Debuginfo.repo
yum -y install crash
debuginfo-install kernelStep 9 : Analyse it
To start the crash utility use the command in the below format
crash /var/crash/<timestamp>/vmcore /usr/lib/debug/lib/modules/<kernel>/vmlinux#crash /var/crash/127.0.0.1-2017-01-11-20:46:57/vmcore /usr/lib/debug/lib/modules/3.10.0-327.el7.x86_64/vmlinux
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