[dm-crypt] crypetsetup and GPT partitions

David Christensen dpchrist at holgerdanske.com
Fri Feb 10 17:05:52 CET 2017


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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