Today, I encountered the following error upon booting a newly-provisioned CentOS 6.5 server:

VFS: Unable to mount root fs on unknown-block

This particular error prevented the server from booting. I am not entirely sure how this error came to be, but to resolve this issue, I did the following:

1. Rebooted the system

2. Opened the boot menu (at the prompt, where upon booting it says “Press any key to enter the menu”)

3. Selected a kernel version prior to the latest installed kernel version (the default selection in the boot menu)

4. Then issued the following yum command to re-install the latest kernel:

yum reinstall kernel

5. Restarted the system, on the latest kernel version, without issue.

For reference, this issue occurred once out of several servers that I deployed today. The kernel version was 2.6.32-431.3.1.el6.x86_64