Software RAID: Unable to boot from Second Disk

[Yogeeraj_1]

Dear Experts!

I have done a new "RedHat Enterprise Linux Advanced Server Update 4" installation and most probably done a wrong configuration so that i am not able to both from the second disk which is supposed to be a mirror of the first boot disk. I have configured Software RAID.

Can any one explain why?

I am posting some information that may be useful to you in guiding me on how to fix this.

==========================================
[root@server1 ~]# more /etc/fstab
# This file is edited by fstab-sync - see 'man fstab-sync' for details
/dev/md2 / ext3 defaults 1 1
/dev/md1 /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs defaults 0 0
/dev/md3 /home ext3 defaults 1 2
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0
/dev/md4 /tmp ext3 defaults 1 2
/dev/md5 /var ext3 defaults 1 2
/dev/md0 swap swap defaults 0 0
/dev/hde /media/cdrecorder auto pamconsole,fscontext=system_u:object_r:removable_t,exec,noauto,managed 0 0
[root@server1 ~]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdb2[1] sda2[0]
305152 blocks [2/2] [UU]

md2 : active raid1 sdb5[1]
6289344 blocks [2/1] [_U]

md3 : active raid1 sdb6[1] sda6[0]
4192832 blocks [2/2] [UU]

md5 : active raid1 sdb7[1] sda7[0]
2096384 blocks [2/2] [UU]

md4 : active raid1 sdb8[1] sda8[0]
2096384 blocks [2/2] [UU]

md0 : active raid1 sdb3[1] sda3[0]
20972736 blocks [2/2] [UU]

unused devices:
[root@server1 ~]# cat /etc/yaboot.conf
# yaboot.conf generated by anaconda

boot=/dev/sdb1 /dev/sda1
init-message=Welcome to Red Hat Enterprise Linux AS!\nHit for boot options

partition=2
timeout=20
install=/usr/lib/yaboot/yaboot
delay=5
nonvram

image=/vmlinuz-2.6.9-42.EL
label=linux
read-only
initrd=/mpp-2.6.9-42.EL.img
root=/dev/md2
append="rhgb quiet"

[root@server1 ~]#
==============================================

Thanking you in advance for your insights.

Kind regards
yogeeraj

[Stuart Browne · Accepted solution]

The issue is the grub boot loader.

Software RAID doesn't mirror the boot sector of the hard-drive.

So simply put, once the machine is built, you need to grub-install to the 2nd disks' boot sector to install the boot loader.

Once that's done, after a disk swap, it should successfully boot from the 2nd disk.

[Yogeeraj_1]

Hi,

Thank you Stuart for the prompt response.

>So simply put, once the machine is built, you need to grub-install to the 2nd disks' boot sector to install the boot loader.

Do you have any link to this step?

I have got some guidelines from:
http://togami.com/~warren/guides/remoteraidcrazies/

(too scrary!!)

Below more info on the current partitions:
[root@server1 ~]# parted
GNU Parted 1.6.19
...
Using /dev/sda
(parted) p
Disk geometry for /dev/sda: 0.000-70006.835 megabytes
Disk label type: msdos
Minor Start End Type Filesystem Flags
1 0.031 7.844 primary boot
2 7.844 305.925 primary ext3 raid
3 305.925 20787.231 primary linux-swap raid
4 20787.231 70001.982 extended
5 20787.262 26929.270 logical ext3 raid
6 26929.301 31023.962 logical ext3 raid
7 31023.993 33071.308 logical ext3 raid
8 33071.339 35118.654 logical ext3 raid
9 35118.686 55599.960 logical
(parted) q
Information: Don't forget to update /etc/fstab, if necessary.

[root@server1 ~]# parted /dev/sdb
GNU Parted 1.6.19
...
Using /dev/sdb
(parted) p
Disk geometry for /dev/sdb: 0.000-70006.835 megabytes
Disk label type: msdos
Minor Start End Type Filesystem Flags
1 0.031 7.844 primary boot
2 7.844 305.925 primary ext3 raid
3 305.925 20787.231 primary linux-swap raid
4 20787.231 70001.982 extended
5 20787.262 26929.270 logical ext3 raid
6 26929.301 31023.962 logical ext3 raid
7 31023.993 33071.308 logical ext3 raid
8 33071.339 35118.654 logical ext3 raid
9 35118.686 55599.960 logical
(parted) q
Information: Don't forget to update /etc/fstab, if necessary.

[root@server1 ~]#


Does this imply a copy of the partition table to the second disk:

e.g. sfdisk -d /dev/sda > /tmp/partitions.txt
then

fdisk -d /dev/sdb < /tmp/partitions.txt


Please advise further

kind regards
yogeeraj

[Stuart Browne]

grub-install /dev/sdb

That should be all that's needed once all the raid stuff is set up (which it looks to be).

[Yogeeraj_1]

Hi Stuart!

thanks again for your reply.

[root@server1 ~]# grub-install /dev/sdb
-bash: grub-install: command not found
[root@server1 ~]#


There does not seem to be any grub software installed. Is it another rpm that needs to be added? any other alternatives?

please advise further..

kind regards
yogeeraj

[Rob Leadbeater]

Hi,

Maybe it's just a path thing... You could try:

# /sbin/grub-install /dev/sdb

Failing that, this RedHat article may help...

http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/en-US/System_Administration_Guide/s2-rescuemode-boot-reinstall-bootloader.html

Cheers,

Rob

[skt_skt]

#whereis grub-install
grub-install: /sbin/grub-install /usr/share/man/man8/grub-install.8.gz
#rpm -qa|grep -i grub
grub-0.95-3.8

[Yogeeraj_1]

hi to all,

thank you for the responses.

Just want to clarify. I do not have the grub-install package installed on the system. But it seems to me that the bootloader does not use the grub configuration. Using yaboot instead.


[root@server1 ~]# yabootconfig --help
Usage: yabootconfig [OPTION]...
Generate a working /etc/yaboot.conf.

-t, --chroot set root directory yabootconfig should work from
-r, --root set root partition, Example: /dev/hda3
default: determined from {chroot}/etc/fstab
-b, --boot set bootstrap partition, Example: /dev/hda2
default: first type: Apple_Bootstrap partition
-C, --config set config file name (Example: /etc/yaboot.conf)
--kernel-args add an append= line with specified arguments
-q, --quiet don't ask any questions/confirmation
--noinstall don't automatically run mkofboot
-h, --help display this help and exit
-V, --version output version information and exit
[root@server1 ~]#


correct me if i am wrong.

i do not want to take risk of mess up everything by installing the grub-install rpm.

please advise

kind regards
yogeeraj

[Stuart Browne]

Ah, boot loader I've never used before!

http://www.linux-sxs.org/storage/raid_setup.html

In particular the section near 'Example yaboot.conf:'.