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I have a VMWare Redhat machine that I need to change the SCSI controller on the machine from a LSI Logic Parallel to LSI Logic SAS. I have done this through vmware, but now when the box tries to boot it kernel panics saying that it cant mount /dev/root

Can anyone help with this as I am unable to find much information on it and really dont want to rebuild the machine.


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If it's RHEL 5 or 6, then don't use any of the two LSI controllers in virtual machine definition. Use the paravirtualised storage driver.

See this VMware KB article for the supported configurations and migration procedure.

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The LSI Logic SAS virtual controller is really only there for Windows 2008 to allow for clustering. Use one of the other virtual controllers instead.

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We are getting better performance on this controller rather than anything thought the logical step would be to move controllers? – ard Jul 31 '11 at 14:26

The problem is that, when the system boots up, an initial ram disk is created from the contents of a file which contains certain drivers the system needs to continue booting. If that initial ram disk file doesn't contain the drivers for your system, the system will not able to boot. To resolve this, you'll need to rebuilt the initrd file using the following procedure:

  1. Boot the system into rescue mode from the installation disc and chroot /mnt/sysimage
  2. Backup your /etc/modprobe.conf file and replace any scsi_hostadapter entries in it with the following:

    alias scsi_hostadapter mptbase alias scsi_hostadapter1 mptspi

Create an initial ram disk

  1. cd /boot
  2. mv initrd-.img initrd-.img.bak (replace * with actual file name)
  3. mkinitrd -v -f /boot/initrd-*.img * (replace both instances of * with actual version number in the file you just renamed)
  4. Reboot the system

If you need to revert for any reason, simply boot back into rescue mode and revert /etc/modprobe.conf and the initrd-*.img file, then reboot.

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