[dm-crypt] cryptsetup creates 1.8 Gb when it should be 1Tb

Arno Wagner arno at wagner.name
Mon Oct 28 03:54:32 CET 2013


Looks like some bizarre bug to me. Or maybe you have a faked
drive that actually is only 2GB? It has happened to some people
in the past. Example:

 http://www.thetechtip.com/the-fake-500gb-hard-drive-from-china/

In this case, maybe the device mapper does some check that the
counterfitters have not anticipated and deduces a correct size.

Maybe post more info:
- What type of drive
- smartctl -i for that drive
- what kernel
- what cryptsetup version

Arno

On Mon, Oct 28, 2013 at 03:05:23 CET, metageek wrote:
> I've checked the FAQ, but this does not seem to be answered there...
> 
> I'm creating an encrypted partition on a portable USB3 drive. The drive is
> 1Tb and I've allocated all on a single partition:
> 
> Disk /dev/sdb: 1000.2 GB, 1000204885504 bytes
> 255 heads, 63 sectors/track, 121601 cylinders, total 1953525167 sectors
> Units = sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disk identifier: 0x9f0bf2e1
> 
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sdb1              63  1953525166   976762552   83  Linux
> 
> Then I went on to create the LUKS encryption:
> 
> cryptsetup luksFormat /dev/sdb1
> 
> then open it:
> 
> cryptsetup luksOpen /dev/sdb1 pjhomecrypt
> 
> now using status to see its properties:
> 
> cryptsetup -v status pjhomecrypt         
> /dev/mapper/pjhomecrypt is active.
>   type:    LUKS1
>   cipher:  aes-cbc-essiv:sha256
>   keysize: 256 bits
>   device:  /dev/loop0
>   loop:    /dev/sdb1
>   offset:  4096 sectors
>   size:    3752880 sectors
>   mode:    read/write
> Command successful.
> 
> I see there are only 3752880 sectors at 512 bytes, this is only about 1.8 Gb!
> 
> creating an ext4 filesystem on this, and mounting it shows the same...:
> 
> mkfs.ext4 /dev/mapper/pjhomecrypt
> mke2fs 1.42.6 (21-Sep-2012)
> Filesystem label=
> OS type: Linux
> Block size=4096 (log=2)
> Fragment size=4096 (log=2)
> Stride=0 blocks, Stripe width=0 blocks
> 117360 inodes, 469110 blocks
> 23455 blocks (5.00%) reserved for the super user
> First data block=0
> Maximum filesystem blocks=482344960
> 15 block groups
> 32768 blocks per group, 32768 fragments per group
> 7824 inodes per group
> Superblock backups stored on blocks: 
>         32768, 98304, 163840, 229376, 294912
> 
> Allocating group tables: done                            
> Writing inode tables: done                            
> Creating journal (8192 blocks): done
> Writing superblocks and filesystem accounting information: done
> mount /dev/mapper/pjhomecrypt /mnt
> df -Th /mnt
> Filesystem              Type  Size  Used Avail Use% Mounted on
> /dev/mapper/pjhomecrypt ext4  1.8G  2.7M  1.7G   1% /mnt
> 
> So I only have 1.8Gb out of the 1Tb drive.
> I've googled and can't find anyone with similar problems, so I must be
> missing something here, though I haven't figured it out.
> 
> Can anyone help here?
> 
> _______________________________________________
> dm-crypt mailing list
> dm-crypt at saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt

-- 
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
----
There are two ways of constructing a software design: One way is to make it
so simple that there are obviously no deficiencies, and the other way is to
make it so complicated that there are no obvious deficiencies. The first
method is far more difficult.  --Tony Hoare


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