Am 10.02.2017 um 19:23 schrieb David Christensen:
On 02/10/17 08:22, Sven Eschenberg wrote:
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@xxxxxxxxxxxxxxxx (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@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@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
That's the size of the filesystem afterall.
D'oh!
Lookt at blockdev --report to see the blockdev sizes (i.e. physical
disk, partition, crypt device).
RTFM blockdev(8):
2017-02-10 10:01:08 root@cd2533 ~
# blockdev --report /dev/sda /dev/sda1 /dev/mapper/i3000d_crypt
RO RA SSZ BSZ StartSec Size Device
rw 256 512 4096 0 3000592982016 /dev/sda
rw 256 512 4096 2048 3000591450112 /dev/sda1
rw 256 512 4096 0 3000589352960 /dev/mapper/i3000d_crypt
So, it looks like LUKS consumes:
3000591450112 - 3000589352960 = 2097152 = 2 MB
Thanks for the correction. :-)
Check against dmsetup
RTFM dmsetup(8):
2017-02-10 10:14:06 root@cd2533 ~
# dmsetup info /dev/mapper/i3000d_crypt
Name: i3000d_crypt
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 1
Major, minor: 254, 2
Number of targets: 1
UUID: CRYPT-LUKS1-<redacted>-i3000d_crypt_unformatted
--table
RTFM dmsetup(8), the --table option requires a <table> value. WAG:
2017-02-10 10:14:17 root@cd2533 ~
# dmsetup info --table LIVE /dev/mapper/i3000d_crypt
Name: i3000d_crypt
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 1
Major, minor: 254, 2
Number of targets: 1
UUID: CRYPT-LUKS1-<redacted>-i3000d_crypt_unformatted
I'm not sure what I am checking...
My bad, it is just dmsetup table - this dumps all (active) devicemapper
targets with all essential data ... you can basically take a look at
where in the drive a mapping starts, how long it is etc. . The output
includes the key for crypt targets and whatever additional data each
type of target offers. It sometimes helps to understand the exact layout
better (You'll need to know/understand those numbers however). Just in
case you think you hit some inconsistency or the like. No need however
to post it here.
David
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As you know by now, the size of the crypto target (the device size
available to the filesystem) is just 2MBytes less than the partition
size. So maybe check again on the filesystem size (use the corresponding
filesystem tools if necessary). If you did not increase the device size
at any time after fs creation, then somehow your mkfs did something
wrong. Depending on the fs, if you have a backup of the data, you could
try growing the fs to the full size of the container.
Regards
-Sven
P.S.: Usually df reports the available space to files AFAIK, this should
be roughly devicesize-metadatasize, where metadata is internal
filesystem structures but not filenames and the like (inode space). But
I cannot tell for 100%. I.E.: for a 16GB filesystem I have a difference
of roughly 10 MBytes. (Depends certainly on the filesystem used ...)
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