[dm-crypt] crypetsetup and GPT partitions

Sven Eschenberg sven at whgl.uni-frankfurt.de
Fri Feb 10 17:22:19 CET 2017


That's the size of the filesystem afterall.

Lookt at blockdev --report to see the blockdev sizes (i.e. physical 
disk, partition, crypt device).
Check against dmsetup --table

Those sectors certainly did not just disappear.


Regards

-Sven



Am 10.02.2017 um 17:05 schrieb David Christensen:
> On 02/10/17 01:07, Michael Kjörling wrote:
>> On 10 Feb 2017 00:15 -0800, from dpchrist at holgerdanske.com (David
>> Christensen):
>>> The available space of the LUKS mapped device is going to be smaller
>>> than the partition size.  On one of my 3 TB drives, it's about ~44
>>> GB smaller (~1.6%).  The LUKS meta-data is going to be in there,
>>> including the header.
>>
>> That doesn't make sense. The LUKS header is a shade over 1 MiB,
>> depending on the specific options (the FAQ has details). The size of
>> the header isn't related to the size of the container. Something else
>> is going on in your case.
>
> Here's the data:
>
> 2017-02-10 07:38:40 root at cd2533 ~
> # parted /dev/sda u s p
> Model: ATA ST3000DM001-1ER1 (scsi)
> Disk /dev/sda: 5860533168s
> Sector size (logical/physical): 512B/4096B
> Partition Table: gpt
>
> Number  Start  End          Size         File system  Name     Flags
>  1      2048s  5860532223s  5860530176s               primary
>
> 2017-02-10 07:40:57 root at cd2533 ~
> # df | egrep 'File|mnt'
> Filesystem                1K-blocks      Used  Available Use% Mounted on
> /dev/mapper/i3000d_crypt 2884281560 848596104 1889172304  31% /mnt/i3000d
>
>
> Here's the math:
>
>    5860530176 s / (2 s/kB) - 2884281560 kB
>  = 2930265088 kB           - 2884281560 kB
>  = 45983528 kB
> ~= 44905.8 MB
>
>
> David
>
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