Public bug reported:
Ubuntu 26.04 kdump reports ready and the crash image is loaded, but a
deliberate SysRq panic does not produce a vmcore. The normal kernel
returns through firmware boot about 13 seconds later. The capture kernel
does not reach its systemd dump service.
Expected:
A controlled panic should boot the preloaded capture kernel, save dmesg and a
compressed vmcore under /var/crash, then reboot normally.
Actual:
SSH drops immediately after the panic. The machine returns with a new boot ID
about 13 seconds later, but /var/crash contains no timestamped directory,
dmesg, or vmcore. I added a diagnostic ExecStartPre to kdump-tools-dump.service
which writes a marker to the persistent root filesystem. The marker is never
created, locating the failure before capture-kernel userspace reaches that
service.
Environment:
- Ubuntu Server 26.04 LTS
- linux-image-7.0.0-28-generic 7.0.0-28.28
- GMKtec M5 Ultra; AMD Ryzen 7 7730U
- UEFI; Secure Boot disabled
- ext4 root on NVMe
- kdump-tools 1:1.10.7ubuntu3
- kexec-tools 1:2.0.32-3ubuntu1
- makedumpfile 1:1.7.7-1
Before every test:
- kdump-config: current state ready to kdump
- kexec_crash_loaded=1
- kexec_crash_size=805306368 (768 MiB)
- estimated requirement 609-621 MiB
- over 200 GiB free in /var/crash
Reproduction:
1. Verify `sudo kdump-config show` says ready.
2. Verify `cat /sys/kernel/kexec_crash_loaded` returns 1.
3. While idle, run as root: `sync; echo c > /proc/sysrq-trigger`.
4. Wait for the normal OS to return and inspect /var/crash.
Reproduced three times. Tested Ubuntu's legacy loader (`kexec -p`) and
file syscall (`kexec -p -s`). Also isolated the capture kernel with:
`reset_devices systemd.unit=kdump-tools-dump.service nr_cpus=1 irqpoll
usbcore.nousb nomodeset modprobe.blacklist=amdgpu amd_iommu=off
nmi_watchdog=0 softlockup_panic=0 hardlockup_panic=0 panic=60`
All variants behave identically. Production uses `panic=10`; the timing
is consistent with crash-kexec failing or returning followed by fallback
reboot, but this is an inference because no early console/pstore trace
exists.
An SP5100 TCO watchdog is set to 300 seconds. bootstatus does not show
watchdog expiry and 13 seconds is far below its timeout. An earlier boot
logged `KHO: Failed to reserve lowmem scratch buffer`, similar to LP
#2152152; later boots no longer log it, but kdump still fails.
The attached Apport data was collected directly on the affected host
with `ubuntu-bug linux --save`.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-28-generic 7.0.0-28.28
ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version k7.0.0-28-generic.
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/controlC1',
'/dev/snd/hwC1D0', '/dev/snd/pcmC1D0c', '/dev/snd/pcmC1D0p',
'/dev/snd/by-path', '/dev/snd/controlC0', '/dev/snd/hwC0D0',
'/dev/snd/pcmC0D8p', '/dev/snd/pcmC0D7p', '/dev/snd/pcmC0D3p', '/dev/snd/seq',
'/dev/snd/timer'] failed with exit code 1:
CRDA: N/A
Card0.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer'
Card0.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer'
Card1.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer'
Card1.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer'
CasperMD5CheckResult: pass
CurrentDmesg: Error: command ['dmesg'] failed with exit code 1: dmesg: read
kernel buffer failed: Operation not permitted
Date: Sat Jul 25 21:13:16 2026
InstallationDate: Installed on 2026-07-20 (5 days ago)
InstallationMedia: Ubuntu-Server 26.04 "Resolute Raccoon" - Release amd64
(20260420.1)
MachineType: GMKtec M5 Ultra
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
XDG_RUNTIME_DIR=<set>
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-28-generic
root=UUID=3557381f-c3ad-49df-bc8a-afbbb3c0d6b2 ro nmi_watchdog=1
softlockup_panic=1 hardlockup_panic=1 panic=10 crashkernel=768M
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
acpidump:
dmi.bios.date: 05/09/2026
dmi.bios.release: 1.6
dmi.bios.vendor: American Megatrends International, LLC.
dmi.bios.version: M5 Ultra 1.06
dmi.board.asset.tag: Default string
dmi.board.name: GMKtec
dmi.board.vendor: GMKtec
dmi.board.version: Version 1.0
dmi.chassis.asset.tag: Default string
dmi.chassis.type: 35
dmi.chassis.vendor: Default string
dmi.chassis.version: Default string
dmi.ec.firmware.release: 1.7
dmi.modalias:
dmi:bvnAmericanMegatrendsInternational,LLC.:bvrM5Ultra1.06:bd05/09/2026:br1.6:efr1.7:svnGMKtec:pnM5Ultra:pvrVersion1.0:rvnGMKtec:rnGMKtec:rvrVersion1.0:cvnDefaultstring:ct35:cvrDefaultstring:skuM5Ultra-001:pfaMINI:
dmi.product.family: MINI
dmi.product.name: M5 Ultra
dmi.product.sku: M5 Ultra-001
dmi.product.version: Version 1.0
dmi.sys.vendor: GMKtec
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute
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https://bugs.launchpad.net/bugs/2161812
Title:
[Ubuntu 26.04] kdump crash kernel never reaches userspace after SysRq
panic on AMD Ryzen 7 7730U
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