Re: BTRFS and debian
Le 14/07/2018 à 02:49, David Christensen a écrit :
# 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).
As expected. /dev/sda2 contains raw encrypted data which appear as
random data. It is the purpose of encryption that one cannot see the
real contents.
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.
I forgot to mention another case, although you are not concerned :
- logical partitions numbers and synthetic PARTUUIDs may change when
creating or deleting another logical partition on the same disk. Yet
another reason to not use logical partitions and prefer GPT if you need
more than 4 partitions.
Reply to: