removing raid 1 rendered server unbootable

dime111 · 09-06-2012, 08:02 AM

Hello
Well i tried removing raid array on our server and baaaam
i did not need the server hard drive to be in raid anymore
it was raid 1 and two hard disk each with three partition
so we had :

md0 swap
md1 /boot
md2 /

i used following method to remove raid
removed /etc/mdadm.conf then
mdadm --zero-superblock /dev/md0
mdadm --zero-superblock /dev/md1
mdadm --zero-superblock /dev/md2

and rebooted an then the disaster
the server is not booting anymore
i have access to rescue system so tried mounting the partition and chrooted
and tried fixing grub via

grub-install /dev/sda

did not work also in my fstab i still have refrence to md`s as partition name
so i tried renaming them to sda[1-3]and nothing

so what else can be done to revive the server ?
i thought mdadm --zero-superblock is safe to use

though now im totally confused on how really raid , partition table and type and namings are in such a configuration
regards

business_kid · 09-06-2012, 08:10 AM

I'd suggest booting from an install cd and going at the files(grub.conf, fstab) from there.

dime111 · 09-06-2012, 11:56 AM

well still no luck getting server to boot
any other idea or work around ?

business_kid · 09-06-2012, 12:04 PM

Still no luck doesn't tell us much. Have you set up a live cd to boot, and tried to boot from it? If it didn't work, what happened? What does it say?

dime111 · 09-06-2012, 01:03 PM

sorry
well i do not have visual on server
just i have booted server on data center rescue console and mounted my partitions and chrooted
so in fact i cant see at which stage server hangs
current information

Quote:

proc /proc proc defaults 0 0
none /dev/pts devpts gid=5,mode=620 0 0
/dev/sda1 none swap sw 0 0
/dev/sda2 /boot ext3 defaults 0 0
/dev/sda3 / ext3 defaults 0 0

Quote:

Disk /dev/sda: 300.0 GB, 300069052416 bytes
64 heads, 32 sectors/track, 286168 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes

Device Boot Start End Blocks Id System
/dev/sda1 2 2048 2096128 fd Linux raid autodetect
/dev/sda2 2049 2304 262144 fd Linux raid autodetect
/dev/sda3 2305 286168 290676736 fd Linux raid autodetect

Disk /dev/sdb: 300.0 GB, 300069052416 bytes
64 heads, 32 sectors/track, 286168 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 286168 293036016 83 Linux

and strange enteries which i think because i installed grub on both hard

Quote:

root@rescue /home # df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md2 276G 173G 89G 67% /
none 10M 76K 10M 1% /dev/pts
/dev/sda2 276G 173G 89G 67% /amir
/dev/sda2 276G 173G 89G 67% /boot
/dev/sda2 276G 173G 89G 67% /amir

GRUB
i changed from md2 to sda2

Quote:

# GRUB bootloader configuration file
#

timeout 5
default 0

title CentOS (2.6.18-308.11.1.el5)
root (hd0,1)
kernel /vmlinuz-2.6.18-308.11.1.el5 ro root=/dev/sda2
initrd /initrd-2.6.18-308.11.1.el5.img

title CentOS (2.6.18-274.12.1.el5)
root (hd0,1)
kernel /vmlinuz-2.6.18-274.12.1.el5 ro root=/dev/md2
initrd /initrd-2.6.18-274.12.1.el5.img

title CentOS Linux (2.6.18-274.7.1.el5PAE)
root (hd0,1)
kernel /boot/vmlinuz-2.6.18-274.7.1.el5PAE ro root=/dev/md2
initrd /boot/initrd-2.6.18-274.7.1.el5PAE.img

chrism01 · 09-06-2012, 07:03 PM

This is what I would have tried (after doing a backup; use at your own risk; untested)

Code:

# 2 steps to 'remove' 2nd disk
mdadm --fail /dev/md0 /dev/sdb1
mdadm --remove /dev/md0 /dev/sdb1

# Tell it it's no longer a raid
# (you could probably skip this)
mdadm --zero-superblock /dev/md0

# change partitions types from fd=raid to 83=linux, 82 =swap
fdisk /dev/sdb   -  set to what ever

# You'll probably need to switch to a rescue disk at this point,
# as you are fooling with your new system  disk
fdisk /dev/sda   - this is your boot-able system

# test mount each disk + partition to check eg
mount /dev/sda1 /mnt/test
umount /dev/sda1
mount /dev/sdb1 /mnt/test
etc
etc

# backup conf
mv /etc/mdadm.conf{,.old}

# fix up fstab
vim /etc/fstab

# fixup grub.conf
vim boot/grub/grub.conf

dime111 · 09-07-2012, 04:39 AM

hello
thank you i will tried the steps you mentioned
i created back up and moved to another server so i can totally mess with this server now
just about two last steps

Quote:

# fix up fstab
vim /etc/fstab

# fixup grub.conf
vim boot/grub/grub.conf

can you be more specefic on what the fixes should look like ?
regards

chrism01 · 09-09-2012, 08:27 PM

That's specific to your system, but basically you are replacing your old system/boot disk eg /dev/md0, with the 'new' one eg /dev/sda1.
HTH