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Chapter 15. Supported kdump configurations and targets

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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.

With the provided information and procedures, you understand the supported configurations and targets on your Red Hat Enterprise Linux 9 systems and properly configure kdump and validate it’s working.

15.1. 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 find out 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.

Table 15.1. Minimum amount of reserved memory required for kdump
ArchitectureAvailable MemoryMinimum Reserved Memory

AMD64 and Intel 64 (x86_64)

1 GB to 4 GB

192 MB of RAM

4 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 (ppc64le)

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 (s390x)

1 GB to 4 GB

192 MB of RAM

4 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 may vary due to other factors such as I/O devices. Using not enough of memory might cause that a debug kernel is not able to boot as a capture kernel in case of a kernel panic. To avoid this problem, sufficiently increase the crash kernel memory.

15.2. Minimum threshold for automatic memory reservation

The kexec-tools utility, by default, configures the crashkernel command line parameter and reserves a certain amount of memory for kdump. On some systems however, it is still possible to allocate memory for kdump either by using the crashkernel=auto parameter in the boot loader configuration file, or by enabling this option in the graphical configuration utility. For this automatic reservation to work, a certain amount of total memory needs to be available in the system. The memory requirement varies based on the system’s architecture. If the system memory is less than the specified threshold value, you must configure the memory manually.

Table 15.2. Minimum amount of memory required for memory reservation
ArchitectureRequired Memory

AMD64 and Intel 64 (x86_64)

1 GB

IBM Power Systems (ppc64le)

2 GB

IBM  Z (s390x)

1 GB

64-bit ARM

1 GB


The crashkernel=auto option in the boot command line is no longer supported on RHEL 9 and later releases.

15.3. Supported kdump targets

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.

Table 15.3. kdump targets on RHEL 9
Target typeSupported TargetsUnsupported Targets

Physical Storage

  • Logical Volume Manager (LVM).
  • Thin provisioning volume.
  • Fibre Channel (FC) disks such as qla2xxx, lpfc, bnx2fc, and bfa.
  • An iSCSI software-configured logical device on a networked storage server.
  • The mdraid subsystem as a software RAID solution.
  • Hardware RAID such as smartpqi, hpsa, megaraid, mpt3sas, aacraid, and mpi3mr.
  • SCSI and SATA disks.
  • iSCSI and HBA offloads.
  • Hardware FCoE such as qla2xxx and lpfc.
  • Software FCoE such as bnx2fc. For software FCoE to function, additional memory configuration might be required.
  • Software iSCSI with iBFT. Currently supported transports are bnx2i, cxgb3i, and cxgb4i.
  • Software iSCSI with hybrid device driver such as be2iscsi.
  • Fibre Channel over Ethernet (FCoE).
  • Legacy IDE.
  • GlusterFS servers.
  • GFS2 file system.
  • Clustered Logical Volume Manager (CLVM).
  • High availability LVM volumes (HA-LVM).


  • Hardware using kernel modules such as igb, ixgbe, ice, i40e, e1000e, igc, tg3, bnx2x, bnxt_en, qede, cxgb4, be2net, enic, sfc, mlx4_en, mlx5_core, r8169, atlantic, nfp, and nicvf on 64-bit ARM architecture only.
  • Hardware using kernel modules such as sfc SRIOV, cxgb4vf, and pch_gbe.
  • IPv6 protocol.
  • Wireless connections.
  • InfiniBand networks.
  • VLAN network over bridge and team.


  • Kernel-based virtual machines (KVM).
  • Xen hypervisor in certain configurations only.
  • ESXi 6.6, 6.7, 7.0.
  • Hyper-V 2012 R2 on RHEL Gen1 UP Guest only and later version.


The ext[234]fs, XFS, virtiofs, and NFS file systems.

The Btrfs file system.


  • BIOS-based systems.
  • UEFI Secure Boot.

Additional resources

15.4. Supported kdump filtering levels

To reduce the size of the dump file, kdump uses the makedumpfile core collector to compress the data and also exclude unwanted information, for example, you can remove hugepages and hugetlbfs pages by using the -8 level. The levels that makedumpfile currently supports can be seen in the table for Filtering levels for `kdump` .

Table 15.4. Filtering levels for kdump


Zero pages


Cache pages


Cache private


User pages


Free pages

Additional resources

15.5. Supported default failure responses

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

Attempt to save the core dump to the root file system. This option is especially useful in combination with a network target: if the network target is unreachable, this option configures kdump to save the core dump locally. The system is rebooted afterwards.
Reboot the system, losing the core dump in the process.
Halt the system, losing the core dump in the process.
Power off the system, losing the core dump in the process.
Run a shell session from within the initramfs, allowing the user to record the core dump manually.
Enable additional operations such as reboot, halt, and poweroff actions after a successful kdump or when shell or dump_to_rootfs failure action completes. The default final_action option is reboot.
Specifies the action to perform when a dump might fail in the event of a kernel crash. The default failure_action option is reboot.

15.6. Using final_action parameter

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.


  1. To configure final_action, edit the /etc/kdump.conf file and add one of the following options:

    • final_action reboot
    • final_action halt
    • final_action poweroff
  2. Restart the kdump service for the changes to take effect.

    # kdumpctl restart

15.7. Using failure_action parameter

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, which reboots the system.

The parameter recognizes the following actions to take:

Reboots the system after a dump failure.
Saves the dump file on a root file system when a non-root dump target is configured.
Halts the system.
Stops the running operations on the system.
Starts a shell session inside initramfs, from which you can manually perform additional recovery actions.


  1. To configure an action to take if the dump fails, edit the /etc/kdump.conf file and specify one of the failure_action options:

    • failure_action reboot
    • failure_action halt
    • failure_action poweroff
    • failure_action shell
    • failure_action dump_to_rootfs
  2. Restart the kdump service for the changes to take effect.

    # kdumpctl restart
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