红帽全球峰会15.7. Testing the kdump configuration
After configuring kdump, you must manually test a system crash and ensure that the vmcore file is generated in the defined kdump target. The vmcore file is captured from the context of the freshly booted kernel. Therefore, vmcore has critical information for debugging a kernel crash.
Do not test kdump on active production systems. The commands to test kdump will cause the kernel to crash with loss of data. Depending on your system architecture, ensure that you schedule significant maintenance time because kdump testing might require several reboots with a long boot time.
If the vmcore file is not generated during the kdump test, identify and fix issues before you run the test again for a successful kdump testing.
If you make any manual system modifications, you must test the kdump configuration at the end of any system modification. For example, if you make any of the following changes, ensure that you test the kdump configuration for an optimal kdump performances for:
- Package upgrades.
- Hardware level changes, for example, storage or networking changes.
- Firmware upgrades.
- New installation and application upgrades that include third party modules.
- If you use the hot-plugging mechanism to add more memory on hardware that support this mechanism.
-
After you make changes in the
/etc/kdump.confor/etc/sysconfig/kdumpfile.
Prerequisites
- You have root permissions on the system.
-
You have saved all important data. The commands to test
kdumpcause the kernel to crash with loss of data. - You have scheduled significant machine maintenance time depending on the system architecture.
Procedure
Enable the
kdumpservice:# kdumpctl restartCheck the status of the
kdumpservice with thekdumpctl:# kdumpctl status kdump:Kdump is operationalOptionally, if you use the
systemctlcommand, the output prints in thesystemdjournal.Start a kernel crash to test the
kdumpconfiguration. Thesysrq-triggerkey combination causes the kernel to crash and might reboot the system if required.# echo c > /proc/sysrq-triggerOn a kernel reboot, the
address-YYYY-MM-DD-HH:MM:SS/vmcorefile is created at the location you have specified in the/etc/kdump.conffile. The default is/var/crash/.
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