Red Hat Summit17장. Supported kdump configurations and targets
The kdump mechanism is a feature of the Linux kernel that generates a crash dump file when a kernel crash occurs. The kernel dump file has critical information that helps to analyze and determine the root cause of a kernel crash. The crash can be because of various factors, hardware issues or third-party kernel modules problems, to name a few.
By using the provided information and procedures, you can perform the following actions:
- Identify the supported configurations and targets for your Red Hat Enterprise Linux systems.
- Configure kdump.
- Verify kdump operation.
17.1. Memory requirements for kdump
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.
| Architecture | Available Memory | Minimum Reserved Memory |
|---|---|---|
|
AMD64 and Intel 64 ( | 2 GB to 64 GB | 256 MB of RAM |
| 64 GB and more | 512 MB of RAM | |
| 64-bit ARM (4k pages) | 1 GB to 4 GB | 256 MB of RAM |
| 4 GB to 64 GB | 320 MB of RAM | |
| 64 GB and more | 576 MB of RAM | |
| 64-bit ARM (64k pages) | 1 GB to 4 GB | 356 MB of RAM |
| 4 GB to 64 GB | 420 MB of RAM | |
| 64 GB and more | 676 MB of RAM | |
|
IBM Power Systems ( | 2 GB to 4 GB | 384 MB of RAM |
| 4 GB to 16 GB | 512 MB of RAM | |
| 16 GB to 64 GB | 1 GB of RAM | |
| 64 GB to 128 GB | 2 GB of RAM | |
| 128 GB and more | 4 GB of RAM | |
|
IBM Z ( | 2 GB to 64 GB | 256 MB of RAM |
| 64 GB and more | 512 MB of RAM |
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 automatic configuration of reserved memory based on the total amount of memory in the system is a best effort estimation. The actual required memory might vary due to other factors such as I/O devices. Not using enough memory might cause debug kernel unable to boot as a capture kernel in the case of kernel panic. To avoid this problem, increase the crash kernel memory sufficiently.
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