Chapter 19. 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

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 kdump-utils utility automatically reserves memory for kdump using the crashkernel parameter. However, this requires a minimum amount of system memory, which varies by architecture. If your system’s memory is below the threshold, you must configure the reservation manually.

When a kernel crash occurs, the operating system saves the dump file on the configured or default target location. You can save the dump file either directly to a device, store as a file on a local file system, or send the dump file over a network. With the following list of dump targets, you can know the targets that are currently supported or not supported by kdump.

To reduce dump file size, kdump uses makedumpfile to compress data and exclude unwanted information. See the table for supported filtering levels, such as excluding hugepages.

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.

To perform operations such as reboot, halt, or poweroff after kdump succeeds or fails, use the final_action parameter. The default action is reboot.

To specify the action when a crash dump fails, use the failure_action parameter. The default action is reboot.

The parameter recognizes the following actions to take: