To those reading along who don't already know. My explanation below is
factually inadequate or wrong in various places...
The "type codes" as presented in the various EFI/GUID disk partitioning
tools as 0700, 8200, 8300, EF02, and so on are never written to disk as
such. They are short-hand values (chosen to be deliberately similar to
the MS-DOS partitioning type codes of 07, 82, 83, etc) to select
standardized GUIDs for the partition type field.
So there is the two-digit code from the ms-dos partitoning scheme, then
there are the four-digit codes that let you select which type GUID will
be written in an EFI partition scheme.
The question of "reuse" is still improper as the type codes were
assigned by the EFI standard for specific use as type codes. The EFI
tool used (gdisk, or windows disk partitioning tool, etc) is immaterial
as the result codes are selected by standard.
I could have, and should have, been _way_ more clear, and/or less wrong. 8-)
http://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_type_GUIDs
On 11/29/2014 12:20 AM, Robert White wrote:
On 11/28/2014 11:29 PM, Duncan wrote:
Since I can't/won't run pretty much anything proprietary, there's little
chance of it being taken as anything but Linux, here. (Tho I actually
use (c)gdisk for partitioning here and it appears to use a different
GUID.
(0700 in its short form which AFAIK is gdisk specific, for MS basic data,
while it uses 8300 for general Linux filesystems. I could look up the
long form GUIDs, but meh...)
Partition type codes (e.g. 0700, 8300, EF00, etc) have _nothing_ to do
with UUIDs. They are type codes. They aren't "short form" of anything
else at all. In fact 0700 is the _long_ _form_ of the original code of
"7", but in big-endian order now that it went from one byte to two.
Microsoft started using pre-assigned UUIDs as "classes", e.g. type codes
they could cram into their various registry files. If you actually read
the registry you'll find a lot of places where "rational word" is
defined as {some_uuid_here} and then eslwere {some_uuid_here} has a
bunch of data items attached to it.
So gpartd didn;t "reuse" microsoft UUIDs.
In some/many of the older formats there was a code for "operating system
data" (which I think is what 7 was originally). Others came by and said
"since we're going to put in a type code for "linux swap" (82) then lets
put in a code for linux data as well (83), and all this before the whole
byte expansion to turn these things from bytes into two-byte words.
Once everybody else picked their own type codes for their data
partitions, everybody just started calling "7" microsoft data. And linux
doesn't care at all since it's noise since every partition just ends up
as /dev/[sh]d? anyway.
All this stuff has historical reasons. GNU/Linux attempts to be an
egalitarian actor so it adapts to whatever you do.
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