On 07/13/18 15:36, Pascal Hambourg wrote:
Le 13/07/2018 à 03:13, David Christensen a écrit :
file(1) -- no:
2018-07-12 17:55:01 root@po ~
# file /dev/sda1
/dev/sda1: block special (8/1)
You must add the option -s so that file looks into the special device
file contents.
2018-07-13 17:39:48 root@po ~
# file -s /dev/sda1
/dev/sda1: BTRFS Filesystem label "po_boot", sectorsize 4096, nodesize
16384, leafsize 16384, UUID=6ff0dd1d-8d46-454b-bb35-a09afc47145a,
65490944/999292928 bytes used, 1 devices
2018-07-13 17:39:51 root@po ~
# file -s /dev/sda2
/dev/sda2: data
2018-07-13 17:39:59 root@po ~
# file -s /dev/sda3
/dev/sda3: LUKS encrypted file, ver 1 [aes, xts-plain64, sha256] UUID:
0152d2e2-4cfb-42c4-a121-6fb832962e47
The output for /dev/sda2 is not very informative (e.g. clues that it has
dm-crypt, random key, and swap).
I have been using /dev/disk/by-id/* successfully [in /etc/crypttab] for a while, but
Did the installer automatically wrote this in /etc/crypttab or did you
replace the original device name ?
I edited /etc/crypttab.
/dev/disk/by-partuuid sounds even better -- this will prevent
confusion if and when I move partitions or images to other devices.
Beware that unlike a UUID or LABEL, a PARTUUID or PARTLABEL is stored in
the partition table, not in the partition data.
Also note that a DOS partition table entry does not contain a UUID nor
LABEL, and the PARTUUID is artificially built by combining the 32-bit
"disk identifier" field in the MBR and the partition number. So if the
partition number or the disk identifier changes, the PARTUUID changes.
In short :
- if you move the disk contents (including the partition table) to
another disk, the PARTUUID is preserved ;
- if you move the partition contents to another partition, the PARTUUID
is not preserved.
Thanks for the warning. My typical use-case is to move the entire
system drive image between various 16+ GB devices, so PARTUUID should work.
There is a hackish way to add a UUID to a plain dm-crypt partition :
write metadata of any kind at the beginning of the partition (ext2,
swap, LUKS...) and specify an offset for dm-crypt data beyond the metadata.
Okay.
David