View Full Version : [xubuntu] RAID 5 mdadm superblock and mount on boot help!

November 15th, 2008, 08:30 PM
Hi there. I have a software RAID 5 created with mdadm, I set up a file system with
mke2fs -j /dev/md0 Also edited /etc/fstab to mount /dev/md0 at boot, and edited /etc/mdadm/mdadm.conf to assemble the array. when I reboot, I get an error saying
fsck.ext3: Invalid argument while trying to open /dev/md0
The superblock could not be read or does not describe a correct ext2 filesystem.
If the device is valid and it really contains an ext2 filesystem (and not swap or ufs
or something else), then the superblock is corrupt, and you might try running e2fsck
with an alternate superblock:
e3fsck -b 8193 <device>

fsck died with exit status 8

Once booted, I can assemble the array by hand with:
sudo mdadm --assemble /dev/md0 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1

however, that throws an error:

Failed to mount "3T Volume"
mount: only root can mount /dev/md0 on /jestermount.
/jestermount is a directory I created and has 777 premisions, but I also ran the command with sudo, so I don't understand this error!
I just say "close" to the error and mount it on my own with:
sudo mount /dev/md0

after which the line for /dev/md0 in df -k looks like this:

/dev/md0 2884298328 205940 2737578400 1% /jestermount

So my questions are:

1. How do I fix the superblock problem?
2. How do I get it to mount on boot? Or is the superblock problem the only thing in the way.



November 15th, 2008, 11:15 PM
hi there

1st check if your md device is properly assembled before checking the FS on it ..


sudo mdadm --detail /dev/md0

and see if it is assembled ( post the results when in doubt )

also keep in mind that each block device has it's own superblocks
> the MD superblocks reside on the individual physical devices
> the FS super blocks reside on the MD device
( and if you're using LVM / EVMS ) then these have their own superblocks aswell )

let me know if the MD is ok .. then I'll post some more ... ( I'm pretty good with RAID's check my other posts )

November 16th, 2008, 12:05 AM
I think you have a few errors in how you have your array listed in the fstab:

/dev/md0 /jestermount ext3 defaults 0 2

I think this is what you want in the fstab file as the last line.

I assume you have alread made the mountpoint this way:

sudo mkdir /jestermount

Yes, what does

sudo mdadm -D /dev/md0


And what does your /etc/mdadm/mdadm.conf show?

November 17th, 2008, 06:24 AM
after replacing the line in fstab and a reboot, running the mdadm code gave this:

sudo mdadm -D /dev/md0
mdadm: md device /dev/md0 does not appear to be active.

hmmmm... what now?

November 17th, 2008, 04:34 PM
Gosh, here's what I'd do, exactly. Delete the /etc/mdadm/mdadm.conf file, remove mdadm using apt-get, reboot. Re-install mdadm, then run this:

sudo mdadm --assemble --scan

That will auto re-create the mdadm.conf file and you should be good to go. If your line in the fstab file is not right, see if the mount will work:

sudo mount -a

That should mount the array, if you have the mountpoint correctly made.

Let us know how things go.

November 17th, 2008, 05:52 PM
Sweet! Thanks guys, looks like the auto built /etc/mdadm/mdadm.conf file is a lot better than the one I had before!


DEVICES partitions

# mdadm.conf
# Please refer to mdadm.conf(5) for information about this file.

# by default, scan all partitions (/proc/partitions) for MD superblocks.
# alternatively, specify devices to scan, using wildcards if desired.
DEVICE partitions

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# instruct the monitoring daemon where to send mail alerts

# definitions of existing MD arrays
ARRAY /dev/md0 level=raid5 num-devices=4 UUID=4b07316a:8cd2d897:3abe3a51:4abf35bf

# This file was auto-generated on Mon, 17 Nov 2008 11:26:07 -0500
# by mkconf $Id$

When in doubt, reinstall, reboot! :KS

November 17th, 2008, 09:14 PM
You mean things are normal, with mounted array?

November 17th, 2008, 09:54 PM
Yeah, everything looks normal. I don't receive any errors on boot, and md0 is mounted on /jestermount with 2700GB of storage available! I am actualy trying to set up NFS now, if you have any links you can point me in the direction of, that would be great!

Thanks for all your help!