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. ** Changed in: linux (Ubuntu) Importance: Undecided => High ** Tags added: kernel-da-key -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1653636 Title: Kernel panic - not syncing: VFS: Unable to mount root fs on unknown- block(0,0) Status in linux package in Ubuntu: Confirmed Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1653636/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp