[CentOS] /dev/disk/by-uuid missing

Sun Aug 17 20:30:54 UTC 2014
Michael Schumacher <michael.schumacher at pamas.de>


I got a problem with one of my servers where the boot process fails,
because it cannot find its root partition.

My /boot/grub/grub.conf uses to look like
title CentOS (2.6.32-431.17.1.el6.x86_64)
        root (hd0,0)
        kernel /vmlinuz-2.6.32-431.17.1.el6.x86_64 ro root=UUID=8ef1f6cb-5dfc-497e-83d0-8d91cbbe4939 rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD quiet SYSFONT=latarcyrheb-sun16 rhgb crashkernel=auto rd_NO_DM rd_NO_LVM  KEYBOARDTYPE=pc KEYTABLE=de
        initrd /initramfs-2.6.32-431.17.1.el6.x86_64.img

I could get the system to boot again by just replacing the
"root=UUID-..." part with "root=/dev/sdb3"

when I started looking around, I noticed that the "/dev/disk"by-uuid"
directory was not there. The "by-id" as well as the "by-path"
directories were both there. I tried to create directory and the links
in the directory manually, but they were gone after the next reboot.

I assume that these /dev/disk/ entries are created by some process at
boot time, but I have no clue how this is done nor what is wrong with
my system.

I checked what blkid -L says, but this seems to be OK.
device         fs_type  label     mount point        UUID
/dev/sda1      ext4               /mnt/raid          a574f30b-fa43-4e34-8498-1cb29c4c261f
/dev/sdb1      ext4               /boot              01746f38-6289-4b03-8011-bfac89ed89bd
/dev/sdb2      swap               <swap>             903a51b7-393d-4df9-9b58-f06a0a80a748
/dev/sdb3      ext4               /                  8ef1f6cb-5dfc-497e-83d0-8d91cbbe4939

Any help?

btw., the problem appeared when I installed a 18TB raid array. I had
to compile the e2fsprogs from the most recent sources using this
to install a very large ext4 file system on the raid disk.

best regards
Michael Schumacher
PAMAS Partikelmess- und Analysesysteme GmbH
Dieselstr.10, D-71277 Rutesheim
Tel +49-7152-99630
Fax +49-7152-996333
Geschäftsführer: Gerhard Schreck
Handelsregister B Stuttgart HRB 252024