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Date: Thu, 16 Nov 2023 11:36:13 +0100
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin-patches@cygwin.com
Subject: Re: [PATCH] Cygwin: Add /dev/disk/by-drive and /dev/disk/by-uuid
 symlinks
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Hi Christian,

On Nov 15 18:23, Christian Franke wrote:
> This is the next (and possibly last for now) extension to the /dev/disk
> directory. Limited to disk related entries which allowed a straightforward
> extension of the existing code.
> 
> My original idea was to add also other drive letters and volume GUIDs. Too
> complex for now.
> 
> Interestingly the volume GUID (by-uuid) for partitions on MBR disks is
> sometimes identical to the partition "GUID" (by-partuuid), sometimes (always
> for C:?) not. With GPT disks, both GUIDs are possibly always identical.

That looks great, but in terms of by-uuid, I'm not sure it's the
right thing to do.  On Linux I have a vfat partition (/boot/efi).
The uuid in /dev/disk/by-uuid is the volume serial number, just
with an extra dash, i.e.

  057A-B3A7 -> ../../sda1

That's what you get for FAT/FAT32/exFAT.

I also tried an NTFS partition and the output looks like this:

  0FD4F62866CFBF09 -> ../../sdc1

This is the 64 bit volume serial number as returned by
DeviceIoControl(FSCTL_GET_NTFS_VOLUME_DATA)(*).

Wouldn't that be what we want to see, too?


Thanks,
Corinna


(*) Incidentally the last 8 digits represent the crippled 4 byte
    serial number returned by
    NtQueryVolumeInformationFile(..., FileFsVolumeInformation).