[svlug] Fdisk and Luks partition

Robert Freiberger rfreiberger at gmail.com
Tue Nov 27 22:36:08 PST 2012

I'm studying for the RHCSA exam and having a hard time fully understanding
how to setup a Linux Unified Key Setup partition to mount at boot time.

While I can mount the LUKS partition manually, I seem to have a problem
adjusting the FSCK settings on /etc/fstab. Typically I add the information
using the UUID of the disk, the mount point, ext4, defaults, 1, 2. But upon
boot, I see the following error.

"fsck.ext4: Bad magic number in super-block while trying to open /dev/sde1
The superblock could not be read or does not describe a correct ext2
filesystem. "

I can enter the system and remount the / filesystem, change the setting in
/etc/fstab to boot the system correctly. But I'm not 100% on what is
causing the issue. Is the fact that the filesystems are being mounted in
the wrong order the reason for the failure? If I change the fsck value from
2 to 0, this boots the system correctly, but doesn't fix the issue as the
file system is now unchecked.

I assume that the problem is / filesystem needs to be mounted first, then
it can start the encryption module for LUKS, enabling the reading of the
file containing the passphrase.

Maybe I'm over thinking this?

Here's the /etc/fstab file. The partition in question is the /kuk2 mount.

   1. # /etc/fstab
   2. # Created by anaconda on Sat Oct 20 09:54:31 2012
   3. #
   4. # Accessible filesystems, by reference, are maintained under
   5. # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for
   more info
   6. #
   7. UUID=83a523b1-71b5-4e59-926e-126086d47a9b /
   ext4    defaults        1 1
   8. UUID=332e4077-dcfb-4da6-ad63-bf669c5f7042 /boot
   ext4    defaults        1 2
   9. UUID=e2c66d36-f298-40f2-bd63-78eb2e25f72d swap
    swap    defaults        0 0
   10. tmpfs                   /dev/shm                tmpfs   defaults
      0 0
   11. devpts                  /dev/pts                devpts
    gid=5,mode=620  0 0
   12. sysfs                   /sys                    sysfs   defaults
      0 0
   13. proc                    /proc                   proc    defaults
      0 0
   14. /dev/vg1/lv100          /lv100mnt               ext4    defaults
      1 3
   15. /dev/mapper/sdd1luks    /sdd1luks               ext4    defaults
      1 2
   16. UUID=efd3526d-d776-410d-90b8-fa4016c44220 /luk2  ext4   defaults
      1 2
   17. /dev/sdd3               /share3                 ext4    defaults
      1 4
   18. /dev/sdd4               swap                    swap    defaults
      0 0


Robert Freiberger
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