After a Kernel upgrade and a reboot on our CENTOS 6 server, it tried to boot with the following error: Kernel panic – not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
After a ton of research we concluded that the initramfs was not created correctly during the kernel upgrade.
To fix this issue do the following:
1. Boot into a live same version of Centos. Choose the recovery options.
2. Go through all of the default prompts, then drop down to shell.
3. Type: chroot /mnt/sysimage
4. Type: cd /boot
5. Type: ls -l initramfs*
6. Look at the version numbers and determine the last version that was installed. Eg. initramfs-2.6.32-358.el6.x86_64.img
7. Type: dracut -f /boot/initramfs-2.6.32-358.el6.x86_64.img 2.6.32-358.el6.x86_64
This will rebuild the initramfs. On reboot your system should come back up.