Kernel Panic

Kernel Panic is a term used to denote when a OS cant boot properly or crashed because of a fatal error. This could be because of many reasons like unsupported hardware or missing/corrupted drive or because of unstable updates.It is equivalent of Windows Blue Screen error for UNIX and UNIX based systems.

Kernel Panic sometimes might be caused because of Kernel Oops(In case of error, Kernel will kill the offending process and continue to run). This can be identified with the call trace stack displayed at the time of startup.In these cases, users will be displayed with the grub menu.

Error1: Simplest reason for this panic might be because of less space in /boot folder.Easiest way to fix this issue will be to boot the old kernel from the available list and users can purge old kernels through

sudo apt-get autoremove

and also remove unstable updates.

Error2: “Kernel Panic – not syncing: VFS: Unable to mount root fs on unknown-block(0,0)”
In this case, grub update is needed. Boot old kernel(if available) or use Live CD to boot and run the following commands from any one of the below approach.

Fix 1: Run

dpkg –configure -a

This will update the initramfs hook and fix the broken kernel.
Fix 2: Run

update-initramfs -u -k version

update-grub

Fix 3: This fix can be done when grub is looking in a different path. Find the correct the filesystem where grub is installed using following commands in GRUB prompt(Shift +C during startup),

ls # Should show your drives and partitions hd0,1=sda1
ls (hd0,1)/ # Should include ‘vmlinuz’ and ‘initrd’
ls (hd0,1)/boot/grub # Should see a lot of *.mod files

and then install grub with following commands after booting old kernel/using LiveCD,

sudo mount /dev/sda1 /mnt
sudo grub-install –root-directory=/mnt /dev/sda

Note: 2nd line should have the partition number.