Re: Grub and software raid-1

Yusuf Goolamabbas wrote:

What steps should one take to ensure that Grub correctly sets up the MBR
on /boot if /boot is on a software raid partition. My understanding is
that currently GRUB will only install itself on the first disk even if
/boot is a raid-1 partition so if the first disk dies the system won't
be able to boot

Will Fedora Core 2 take care of this automatically ?

Regards, Yusuf

I can't answer for the "automatically" question. But I can tell you what steps to take to configure the second disk's MBR.

Scenario:  System with two hard drives (sda, sdb) mirrored for redundancy.

The 1st drive in the BIOS is sda and the 2nd drive is sdb. Grub is installed on the MBR of sda during the O/S installation. We need it installed on the MBR of sdb as well in case the 1st drive fails and the system reboots.

The trick is the grub device command issued before the root and setup commands.

While the system is booted up with both drives operational type the following commands as root:

[root@myhost]# grub
grub> device (hd0) /dev/sdb # This will set (hd0) to be the 2nd drive for the subsequent commands
grub> root (hd0,0) # This will set the root device to be the 1st partition of the 2nd drive (location of /boot/grub directory)
grub> setup (hd0) # This will write the boot information to the MBR on the 2nd drive
grub> quit

That's all.

Here's what my session looked like doing the same for hda,hdb mirrors, where the root command in /boot/grub/grub.conf is "root (hd0,0)":
grub> device (hd0) /dev/hdb


grub> root (hd0,0)
Filesystem type is ext2fs, partition type 0xfd


grub> setup (hd0)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd0)"... 16 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd0) (hd0)1+16 p (hd0,0)/grub/stage2 /grub/grub
.conf"... succeeded
Done.

grub> quit

Chris

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  Chris Johnson, RHCE #807000448202021