[svlug] Fdisk and Luks partition

[Marco Walther]

On 11/27/2012 10:36 PM, Robert Freiberger wrote:
> 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 /dev/sde1:
> The superblock could not be read or does not describe a correct ext2 
> filesystem. "
Did you try to use /dev/mapper/luk2 instead of the UUID? It looks like 
you (the boot time fsck) are trying to interpret /dev/sde1 as ext4 
directly?! That will not work. You have to use the device provided by 
the `encryption framework' instead of the `physical partition'.

I have no experience with this, just from reading up on it;-) So take 
everything with a grain of paprika;-)
A ref is @ http://fedoraproject.org/wiki/Implementing_LUKS_Disk_Encryption

Have fun;-)
-- Marco

>
> 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
>     '/dev/disk'
> 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
>
>
> Thanks,
> Robert
>
>
>
> -- 
> Robert Freiberger
> 510-936-1210
>
>
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