Dedoimedo posted a short tutorial explaining how to handle Kernel panic - not syncing: VFS error when booting Kdump kernel, including fixing the Kdump command line and init script, memory allocations under /proc, editing the kernel configuration with additional modules and recreating initrd image.

Say you want to use Kdump in your environment. You setup your machines. Then, you crash your system for testing purposes, in order to see whether Kdump can collect a memory core successfully. However, during the Kdump kernel startup, a panic message appears on the console. It reads: Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0). What do you do now?

There are two variations to this message and many possible reasons to why it shows up. The solution is very simple, but it may not appear that way if you try to debug on your own or hit the Web search for solution. You will find a million threads, all discussing this item, most of them half-baked guesses. Like the Ubuntu initrd issue, the solution is none of the suggested items, so please read and learn how to handle this properly.

  Kernel panic - not syncing: VFS - How to solve