Host fails to mount root file system during boot

Symptoms

• Host does not boot normally.
• A kernel panic error is generated.

• You see a message similar to:

  Kernel Panic: VFS: : unable to mount root fs on 00:00"
  Please append a correct "root=" boot option

Purpose

This article provides steps to recover a host that does not boot because it cannot find the root file system.

Resolution

This issue is most commonly caused by a misconfiguration of the boot parameters or a change in drivers that did not get updated correctly. 

To ensure that the boot parameters and drivers are correctly updated:

1. Reboot the host.

2. At the grub loader prompt select Service Console-troubleshooting mode (ESX 3.x) or Troubleshooting Mode (ESX 4.x). This may allow you to boot and enter the system.
   Note: In cases where the system does not boot in this mode, file a support request with VMware Support and note this KB Article ID in the problem description. For more information on filing a support request, see .

3. Log in to the Service Console as the user root.

4. Run the following commands, according to your respective version of VMware ESX.

   VMware ESX 3.x
   1. Run the following command to update the known PCI settings:

      esxcfg-boot -p

   2. Run the following command to update the boot settings:

      esxcfg-boot -b

   3. Run the following command to reinitialize the boot files:

      esxcfg-boot -r

   VMware ESX 4.x

   Run the following command. The additional steps above in VMware ESX 3.x are no longer required in this version of VMware ESX.

   esxcfg-boot -b

5. Run the following command to reboot the host:

   shutdown -r now

6. Select the default boot menu option