Chapter 18. Supported kdump configurations and targets

For kdump to capture a kernel crash dump and save it for further analysis, a part of the system memory should be permanently reserved for the capture kernel. When reserved, this part of the system memory is not available to the main kernel.

The memory requirements vary based on certain system parameters. One of the major factors is the system’s hardware architecture. To identify the exact machine architecture, such as Intel 64 and AMD64, also known as x86_64, and print it to standard output, use the following command:

uname -m

$ uname -m

With the stated list of minimum memory requirements, you can set the appropriate memory size to automatically reserve a memory for kdump on the latest available versions. The memory size depends on the system’s architecture and total available physical memory.

On many systems, kdump is able to estimate the amount of required memory and reserve it automatically. This behavior is enabled by default, but only works on systems that have more than a certain amount of total available memory, which varies based on the system architecture.

The kexec-tools utility can automatically reserve memory for kdump using the crashkernel=auto parameter. This feature requires a minimum amount of system memory, which varies by architecture. If your system memory is below the specified threshold, you must configure the reservation manually.

Upon a kernel crash, the system saves a dump file to a configured target. You can save the dump file to a local device, a file system, or a network location. This reference lists the storage targets supported by kdump.

Reduce dump file size using the makedumpfile core collector to compress data and exclude unnecessary information. By selecting specific filtering levels, such as removing hugepages, you can optimize storage usage. This reference lists the supported filtering levels for kdump.

By default, when kdump fails to create a core dump, the operating system reboots. However, you can configure kdump to perform a different operation in case it fails to save the core dump to the primary target.

When kdump succeeds or if kdump fails to save the vmcore file at the configured target, you can perform additional operations like reboot, halt, and poweroff by using the final_action parameter. If the final_action parameter is not specified, reboot is the default response.

The failure_action parameter specifies the action to perform when a dump fails in the event of a kernel crash. The default action for failure_action is reboot that reboots the system.

The parameter recognizes the following actions to take: