Add native kdump (kernel crash dump) support to VyOS, configurable via the VyOS CLI, to allow kernel panic analysis on production devices.
The following were confirmed unavailable or non-functional:

- kdump: not configured, /var/crash/ does not exist
- pstore/EFI: mounted but empty after panic
- generate tech-support archive: cannot capture post-panic state
- /var/core/: only captures userspace process crashes, not kernel panics

Verified on VyOS 1.5.0 (circinus), kernel 6.6.128-vyos:

# kexec is present in the kernel:
/proc/sys/kernel/kexec_load_disabled       ### exists
/proc/sys/kernel/kexec_load_limit_panic    ### exists
/proc/sys/kernel/kexec_load_limit_reboot   ### exists

# But crash dump is not configured:
/sys/kernel/kexec_crash_size               ### 0 (no memory reserved)
/sys/kernel/kexec_crash_loaded             ### 0 (no crash kernel loaded)
/var/crash/                                ### does not exist
kdump-tools package                        ### not installed

# Missing kernel config options:
CONFIG_CRASH_DUMP                          ### likely not set
CONFIG_PROC_VMCORE                         ### likely not set

# kexec syscall is available:
CONFIG_KEXEC                               ### present

This means the kernel already has the foundation (CONFIG_KEXEC). The remaining work is to enable CONFIG_CRASH_DUMP, CONFIG_PROC_VMCORE, install kdump-tools, and expose configuration via the VyOS CLI.

REQUESTED IMPLEMENTATION

KERNEL BUILD
Enable the following options in x86_64_vyos_defconfig:

CONFIG_KEXEC=y # already present CONFIG_CRASH_DUMP=y # required — enables kdump
CONFIG_PROC_VMCORE=y # required — exposes /proc/vmcore CONFIG_DEBUG_INFO=y # required — for crash utility analysis

PACKAGE
Include kdump-tools and makedumpfile in the VyOS base image:

ii kdump-tools
ii makedumpfile
ii kexec-tools

Suggested VyOS CLI commands

Configuration mode commands

Enable kdump with memory reservation

set system kdump enable

Set memory reservation for crash kernel (default: auto*)

set system kdump memory '256M'

Set local dump path

set system kdump dump-path '/var/crash'

Optional: send dump to remote host via SSH

set system kdump remote-host '192.0.2.10'
set system kdump remote-path '/dumps/vyos'

Operational mode commands:

Show kdump status

show system kdump

Show existing crash dumps

show system kdump dumps

Suggested output of show system kdump:

kdump status: enabled
crash kernel: loaded
memory reserved: 256M
dump path: /var/crash
last dump: 2026-05-12 10:30:01

GRUB INTEGRATION
Automatically inject the crashkernel= parameter into the VyOS GRUB configuration when kdump is enabled via CLI, without requiring manual edits to grub.cfg:

crashkernel=256M

CONFIG_KEXEC is already present and smoke-tested in the VyOS kernel (T8108). The delta to full kdump support is minimal, primarily CONFIG_CRASH_DUMP and CONFIG_PROC_VMCORE.

The kernel boot parameter infrastructure (T5979) and the kernel upgrade to 6.18 (T8147) are both resolved, meaning all prerequisites for this feature are now in place.