Red Hat Bugzilla – Bug 1303317
4.3.3-303.fc23.x86_64: kernel panic on boot: 'not syncing: VFS: Unable to mount root fs on unknown block (0,0)'
Last modified: 2016-12-20 13:19:31 EST
Description of problem:
On boot or reboot, the kernel 4.3.3-303.fc23.x86_64 panics after selection from the GRUB menu and prior to request for LUKS password to access encrypted parts of disk, including the root filesystem.
The kernel panic ends with the following
end kernel panic - not syncing: VFS: Unable to mount root fs on unknown block (0,0)
The first line of output indicates that the kernel is untainted (as I would expect here - no proprietary drivers or similar).
So far, I've not seen this problem with 4.3.3-301.fc23.x86_64 or earlier kernels.
Version-Release number of selected component (if applicable):
Reasonably. 4 boots since kernel update with 3 kernel panics ending with the same line. It definitely failed on the first reboot following installation of the new kernel. It booted successfully on occasion 2 but I can't reproduce that now and have booted with 4.3.3-301 instead following at least 2 consecutive failures (possibly 3, but at least 2).
Steps to Reproduce:
1. Install 4.3.3-303.fc23.x86_64 as part of system update.
2. Regenerate grub.cfg using grub2-mkconfig -o /boot/grub2/grub.cfg because this does not (ever) happen automatically.
4. Hard poweroff on kernel panic.
5. Boot and repeat as necessary, switching to earlier kernel if the situation seems too hopeless.
Untainted kernel panics with message noted above after display of GRUB menu but prior to request for LUKS password.
Kernel does not panic, boot proceeds as expected and LUKS password is requested so that volumes can be mounted as usual.
Machine uses LVM over LUKS. / is encrypted. /boot is not encrypted.
Command line where LVG is the name of the logical volume group, LOCAL is the name of the logical volume mounted at /usr/local, HOME is the name of the logical volume mounted at /home and OTHER is a logical volume mounted in /mnt/:
BOOT_IMAGE=/vmlinuz-4.3.3-303.fc23.x86_64 root=/dev/mapper/LVG-fedora ro rd.md=0 rd.dm=0 rd.lvm.lv=LVG/swap rd.luks.uuid=luks-<long ID number> vconsole.font=latarcyrheb-sun16 vconsole.keymap=uk rd.lvm.lv=LVG/fedora rd.lvm.lv=LVG/LOCAL rd.lvm.lv=LVG/OTHER rd.lvm.lv=LVG/HOME rhgb quiet
linux16 /vmlinuz-4.3.3-303.fc23.x86_64 root=/dev/mapper/LVG-fedora ro rd.md=0 rd.dm=0 rd.lvm.lv=LVG/swap rd.luks.uuid=luks-<long ID number> vconsole.font=latarcyrheb-sun16 vconsole.keymap=uk rd.lvm.lv=LVG/fedora rd.lvm.lv=LVG/LOCAL rd.lvm.lv=LVG/OTHER rd.lvm.lv=LVG/HOME rhgb quiet
The line for the previous kernel is identical except that it has 301 in place of 303.
Apologies if this bug has been reported. Search appears to be broken at the moment.
95% of the time this is because your grub.cfg is missing the line to load the initramfs or the initramfs file itself is corrupted or incomplete. Each kernel stanza should have both the linux and initrd lines included in it to load the corresponding files. Please attach your grub.cfg file. Also, please attach the output of 'ls -l /boot/initramfs*'
As a side note, if you find yourself having to regenerate the grub.cfg file after a kernel install, that is a sign of your userspace setup being broken. How it is broken I have no idea, but it should not be necessary to run grub2-mkconfig by hand.
Created attachment 1120579 [details]
I just installed kernel 4.3.4-200.fc22 and am facing the same kernel panic.
(screenshot at http://share.pho.to/A0lCh since sysctl -b -1 does not show anything).
My root filesystem is btrfs.
Booting 4.2.8-200 works. I am using it now.
# ls -l /boot/initramfs*
-rw-rw-r--. 1 root root 46570611 May 26 2015 /boot/initramfs-0-rescue-dc2e42bdbf274fd4ab4fc03989cafb0b.img
-rw-r--r--. 1 root root 19292643 Dec 18 07:03 /boot/initramfs-4.2.7-200.fc22.x86_64.img
-rw-r--r--. 1 root root 19305332 Dec 27 15:26 /boot/initramfs-4.2.8-200.fc22.x86_64.img
-rw-r--r--. 1 root root 19373400 Feb 2 20:20 /boot/initramfs-4.3.4-200.fc22.x86_64.img
Attached, you can find /boot/efi/EFI/fedora/grub.cfg
I noticed my grub.cfg did not have the initrdefi line.
Running grub2-mkconfig to regenerate the grub.cfg makes the panic disappear.
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