[CentOS] Grub fallback problem

Wed Jul 29 18:47:22 UTC 2009
Matthias Blankenhaus <matthiasblankenhaus at yahoo.com>

Let's try this again :)

I am running CentOS 5 (core pkgs) / x86_64 using grub 0.97 and I am trying to configure a fallback between two partitions on my local disk, each installed with a CentOS image.   The idea is to be able to install a new test OS image and fall back in case of a problem to the default image.  This is a great grub feature !  Except it does not work for me :(

default saved
fallback 1

title NEW OS
  root (hd0,0)
  kernel /boot/vmlinuz-new root=/dev/sda1 panic=5
  initrd /boot/initrd-new.img
  savedefault fallback

  root (hd0,1)
  kernel /boot/vmlinuz-default root=/dev/sda2
  initrd /boot/initrd-default.img

Grub is installed on /dev/sda1, but not on /dev/sda2.  /dev/sda1 is 
the primary boot partition.  Both partitions are formatted with ext3.

The problem is that the fallback does not work for me.  For instance, if I specify on purpose a wrong root device with the NEW OS, e.g. root=/dev/sda3, then the kernel panics and reboots properly after 5 sec.  However, grub then attempts to boot the NEW OS all over again.  The same is true when I fully boot NEW OS with the right root device and then panic the kernel on purpose.

Now, I have read somewhere that grub requires a default file to get
the savedefault feature working.  However, I could neither find the 'savedefault' command nor the grub default file under /boot/grub or
anywhere else.  One more thing, when I choose the boot title manually
then grub seems to remember my last choice.  In other words, grub is
preserving my last choice from a previous boot.

Am I doing something wrong ?  Do I need to install something in addition to grub 0.97 ?

Your help is much appreciated,

--- On Wed, 7/29/09, Matthias Blankenhaus <matthiasblankenhaus at yahoo.com> wrote:

> From: Matthias Blankenhaus <matthiasblankenhaus at yahoo.com>
> Subject: Grub fallback problem
> To: centos at centos.org
> Date: Wednesday, July 29, 2009, 11:19 AM
> Hi !
> I am running CentOS 5 using grub 0.97