Re: [tlug] mysterious disappearing boot filesystem (update)

[Scott VanDusen <Scott_VanDusen@example.com>]

Hi everyone,

After a few days of fiddling around with LVM2 on Raid5 on this new server I was able to find something interesting about that disappearing boot partition. 

I reinstalled Centos with the following setup: 

primary ata ide /dev/hda1 for /boot filesystem
/dev/hda2 for swap 
2 software raid5 arrays on 3 SATA drives: 
           /dev/sda1, /dev/sdb1, and /dev/sdc1 as /dev/md0 
           /dev/sda2, /dev/sdb2, and /dev/sdc2 as /dev/md1 
on /dev/md0 I created a full physical volume, volume group and a single logical volume for the / filesystem
on /dev/md1 I created another full physical volume, then created a volume group and several logical volumes for the /var /home /tmp etc 
created hot swap SATA /dev/sdd
created backup of /boot onto /dev/sde1 which is 2GB compact flash via USB. This was done from rescue mode when /boot was visible.

After confirming raid arrays had been built and all volume groups were OK in rescue mode, I booted into single user mode off of /dev/hda1. As previously noted, the /boot and swap partitions disappeared during the boot sequence, errors being "device not found or already mounted." The /etc/fstab showed /dev/hda1 as /boot and /dev/hda2 as swap. Once in single user mode, as always nothing showed up in /boot and swapon couldnt find /dev/hda2. However fdisk could show the partition table of /dev/hda.

Looking around the /dev/mapper filesystem where the volume groups were at I stumbled upon 3 files that looked out of place:

/dev/mapper/pdc_edcffdbc
/dev/mapper/pdc_edcffdbc1
/dev/mapper/pdc_edcffdbc2

On a whim I mounted /dev/mapper/pdc_edcffdbc1 on /Temp, and lo and behold there was the /boot data. Also /dev/mapper/pdc_edcffdbc2 turned out to be the swap partition. I updated /etc/fstab and changed /dev/hda1 to /dev/mapper/pdc_edcffdbc1 and swap to /dev/mapper/pdc_edcffdbc2, rebooted, and voila everything works.

Any idea why the mapper was creating these pdc* aliases for /dev/hda1 and /dev/hda2? Maybe something with udev? 

Cheers,
Scott VanDusen

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