Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

[Thomas A. F. Thorne]

On powering my PC up after the holiday break I got a welcome back in the form of a kernel panic. I had completed some upgrades before the holiday and was seeing a restart to use the newly upgraded packages message.

When the PC powered on the Caps Lock and Scroll Lock lights on my keyboard were blinking. After passing through grub and attempting to boot the kernel the boot message ended with the following message (typed out by me by hand, please see the attached photograph of the screen for more details):

Kernel Offset: disabled
---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at arch/x86/kernel/smp.c:125 native_smp_send_reschedule+0x60/0x70(
Modules linked in:
CPU: 0 PID 1: Comm: swapper/0 Not tainted 4.4.21 #1
Hardware name: Gigabyte Technology Cp., Ltd. H81M-DS2V/H81M-DS2V, BIOS F6 08/11/2015
 ...
Call Trace:
 ... dump_stack
 ... warn_slowpath_common
 ... warn_slowpath_null
 ... native_smp_send_rescheduale
 ... trigger_load_balance
 ... scheduler_tick
 ... ? tick_sched_handle.isra
 ... update_process_times
 ... tick_sched_handle.isra

I can type out more of the message if people want but I think the chances of my typing it all in correctly are slim.

I tried to boot using the (recovery mode) version of 4.4.21 and the .old version of 4.4.21 that seemed to have appeared from somewhere. To my eye the problem looked the same in each version. Once I selected 4.4.0-57-generic I was able to complete the boot and begin reporting this bug.

If there are any more steps I can take to aid diagnosis please let me know.
---
ApportVersion: 2.20.1-0ubuntu2.4
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC2: thomasthorne 4613 F.... pulseaudio
 /dev/snd/pcmC1D0p: thomasthorne 4613 F...m pulseaudio
 /dev/snd/controlC1: thomasthorne 4613 F.... pulseaudio
 /dev/snd/controlC0: thomasthorne 4613 F.... pulseaudio
CurrentDesktop: Unity
DistroRelease: Ubuntu 16.04
HibernationDevice: RESUME=UUID=3c3104a1-5ead-4ebf-b2df-f9397f572dca
InstallationDate: Installed on 2015-03-12 (662 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
IwConfig:
 lo no wireless extensions.

 eth1 no wireless extensions.

 eth0 no wireless extensions.
MachineType: Gigabyte Technology Co., Ltd. H81M-DS2V
Package: linux (not installed)
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-57-generic.efi.signed root=/dev/mapper/ubuntu--vg-root ro quiet splash crashkernel=384M-:128M
ProcVersionSignature: Ubuntu 4.4.0-57.78-generic 4.4.35
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-57-generic N/A
 linux-backports-modules-4.4.0-57-generic N/A
 linux-firmware 1.157.6
RfKill:

Tags: xenial
Uname: Linux 4.4.0-57-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dialout dip lpadmin mock plugdev sambashare sudo wireshark
_MarkForUpload: True
dmi.bios.date: 08/11/2015
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: F6
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: H81M-DS2V
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrF6:bd08/11/2015:svnGigabyteTechnologyCo.,Ltd.:pnH81M-DS2V:pvrTobefilledbyO.E.M.:rvnGigabyteTechnologyCo.,Ltd.:rnH81M-DS2V:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: H81M-DS2V
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: Gigabyte Technology Co., Ltd.

[Thomas A. F. Thorne (tafthorne)]

I did not choose the virtualbox package when opening this bug. I wanted to choose some kind of kernel or smp related package but did not know what one to select.

[Thomas A. F. Thorne (tafthorne)]

As an upgrade from one kernel to the other seems to have brought about this problem I am attaching the recent /var/log/apt/history.log file.

[Thomas A. F. Thorne (tafthorne)]

As an upgrade from one kernel to the other seems to have brought about this problem I am attaching the recent /var/log/apt/term.log file.

The more recent version of the file is blank. These files relate to the period of the 16th to power off.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1653636

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

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[Thomas A. F. Thorne (tafthorne)]

I have executed the command `apport-collect 1653636` as requested by brad-figg. I can see that log files have been added.

Note that this command was performed while running 4.4.0-57-generic not the 4.4.21 kernel that causes the issue. It is also worth noting that as the filesystem could not be mounted the kernel panic trace was not recorded to disk and as a result is not included in any of the attached log files.

[Joseph Salisbury (jsalisbury)]

Where did you happen to get the 4.4.21 kernel? That is an upstream kernel and not an official Ubuntu kernel like 4.4.0-57.

It might be good to boot 4.4.0-57 and apply the latest updates.

[Thomas A. F. Thorne (tafthorne)]

I expect I got the kernel the same way I get most of my kernels, though an `apt-get upgrade`. Although I did try and compile a kernel a while ago... I wonder if that got left around as an install option and it was so long since I last rebooted I forgot about it!

Now isn't that a silly thing to do. I will reboot into 4.4.0-57 and apply updates. Then probably remove the upstream kernel or at least try updating it and seeing if it boots then remove it.

[Thomas A. F. Thorne (tafthorne)]

Thank you Joseph, the upstream kernel from months ago was the cause of the issue. I had completely forgotten about it being there and did not recognise the change in version numbering as significant.

I followed the steps outlined in http://askubuntu.com/a/594484/109072 to remove the kernel and a reboot now comepletes cleanly.

The steps I performed were:
> If compiled and installed via make install, you will need to manually remove the following entries:
>
> /boot/vmlinuz*KERNEL-VERSION*
> /boot/initrd*KERNEL-VERSION*
> /boot/System-map*KERNEL-VERSION*
> /boot/config-*KERNEL-VERSION*
> /lib/modules/*KERNEL-VERSION*/
> /var/lib/initramfs/*KERNEL-VERSION*/

Where KERNEL-VERSION for me was 4.4.21*.