[CentOS] trouble booting the system with I2O hardware RAID

Mon Apr 11 19:00:40 UTC 2005
Aleksandar Milivojevic <amilivojevic at pbl.ca>

Aleksandar Milivojevic wrote:
> The system in question has one of I2O Adaptec RAID controllers.  I've 
> configured LVM with one volume group and several volumes.  If I boot 
> into the rescue mode, all looks fine and dandy.  Anaconda finds the 
> installation, and I can access all volumes.
> However, when doing "real" boot, it gets into trouble.  All required 
> modules are loaded from initrd image (as far as I can tell).  The I2O 
> modules are able to locate the RAID devices (I see all partitions 
> reported: /dev/i2o/hda1 (unused), /dev/i2o/hdb1 (/boot), and 
> /dev/i2o/hdb2 (rest of the system under LVM).  The only thing different 
> from rescue mode is that i2o/hda and i2o/hdb are reversed (this is 
> strange, but it shouldn't affect things since /boot partition has a 
> label "/boot", and all the rest is under LVM, so everything should be 
> device name independent).  I have no idea why i2o device drivers behave 
> differently when loaded from initrd image during boot, and by Anaconda 
> during installation.
> The last couple of messages printed on the screen are:
> Creating root device
> Mounting root file system
> kjournald starting. Commit interval 5 seconds
> EXT3-fs: mounted filesystem with ordered data mode.
> mount: error 2 mounting none
> Switching to new root
> WARNING: can't access (null)
> exec of init ((null)) failed!!!: 14
> umount /initrd/dev failed: 2
> Kernel panic - not syncing: Attempted to kill init!

Ah, found it...  I was bitten by that nonsense called file system 
labels.  Again.  And it even might be that LVM volume information was 
also read from the wrong place.  The problem isn't I2O related, and can 
probably happen with any other hardware configuration.

I'll summarize, so that folks with similar problems in the future know 
what to do.


I2O RAID controller with two volumes.  First RAID volume is used for the 
system.  Second RAID volume is used for some data storage.  Since kernel 
assigns them different device names during installation, and when the 
system is booted from the disk after installation, I'll call them 
"system RAID volume" and "data RAID volume".  When I reference device 
names, it is just a reference as what name system saw them in particular 

During installation, i2o device drivers report the volumes in expected 
order.  /dev/i2o/hda is the system RAID volume, /dev/i2o/hdb is the data 
RAID volume.  Exactly the order they are defined in I2O BIOS.  hdb is 
not touched by installation process and it contained single partition 
hdb1.  /boot is installed on hda1 and "/boot" file system label written 
onto it.  hda2 is configured as LVM physical volume with the rest of the 
system (including root partition).

After the installation is done, and system reboots, for whatever strange 
reason data RAID volume is detected as /dev/i2o/hda, and system RAID 
volume as /dev/i2o/hdb.  This should theoretically work fine since 
device names are never used as-is in system's configuration.  However, 
the disks in data RAID volume were previously used (they were not 
clean), and since system detected them first, this was the root of the 
problem.  It seems that those disks had (once apon a time) system on 
them, and set of LVM volumes defined, so that was used instead of the 
"real" information from first RAID volume.  I'm not sure if disks were 
used connected to this I2O controller, or if they were used somewhere 
else and it just appeared that this information fell into the "right" 
spot when RAID volume was assembled.

OK, so I wiped all partitions from data RAID volume.  This time system 
actually boots (because it can see only partitions on system RAID volume 
that it detected as /dev/i2o/hdb, so it reads correct LVM information). 
  But the story does not end here.

I created single partition on data RAID volume (/dev/i2o/hda), defined 
it as LVM physical volume, and created new volume group with single 
logical volume on it.  Created file system, mounted it, updated fstab. 
So far so good.  Reboot.  Ups, the system doesn't boot, and complains 
about duplicate "/boot" labels.  Back into the rescue mode.  And sure 
there it was.  e2label reports that first partition on data RAID volume 
(which is of type LVM and contains LVM physical volume) and first 
partition on system RAID volume (which is of type Linux native and 
contains ext3 file system) both have label "/boot".  Ooops.

Apperently, Anaconda was smart enough to ignore the label on something 
that was not an file system.  Whatever goes on during "real" boot wasn't 
that smart.

Used e2label to wipe out the label from data RAID volume.  This time 
system booted, no problems at all.  For good measure I wiped out logical 
volume/group and physical volume from data RAID volume and recreated 
them (didn't wanted to risk e2label used on something that is not file 
system screw some metadata for LVM).  All is happy now.

It could have saved me tons of time and grief if Anaconda checked during 
install process (and detected) conflicting LVM information and 
conflicting file system labels.  Or if file system labels were randomly 
generated (insted of using mount point names), like the labels usded by 
MD and LVM drivers.

Hopefully this info will be usefull to somebody in the future.

Aleksandar Milivojevic <amilivojevic at pbl.ca>    Pollard Banknote Limited
Systems Administrator                           1499 Buffalo Place
Tel: (204) 474-2323 ext 276                     Winnipeg, MB  R3T 1L7