Subject: Re: bug#22797: Using UUID for vfat file system is impossible
From: [email-masked] (Ludovic Courtès)
To: Alex Kost <[email-masked]>
Cc: [email-masked]
Date: Thu, 25 Feb 2016 19:32:52 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

Alex Kost <[email-masked]> skribis:

> Hello, unlike other file system types, FAT volumes have short UUIDs,
> for example: "58D7-4FA5", but such an UUID cannot be used in an
> operating system declaration:
>
> (file-system
>   (device (uuid "58D7-4FA5"))
>   (title 'uuid)
>   (type "vfat")
>   ;; ...
>   )
>
> because (uuid "58D7-4FA5") errors.

That’s expected.  :-)  I’ve clarified this in 0767f6a:

@@ -6302,7 +6302,12 @@ is interpreted as a partition label name; when it is @code{uuid},
 @code{device} is interpreted as a partition unique identifier (UUID).
 
 UUIDs may be converted from their string representation (as shown by the
-@command{tune2fs -l} command) using the @code{uuid} form, like this:
+@command{tune2fs -l} command) using the @code{uuid} form@footnote{The
+@code{uuid} form expects 16-byte UUIDs as defined in
+@uref{https://tools.ietf.org/html/rfc4122, RFC@tie{}4122}.  This is the
+form of UUID used by the ext2 family of file systems and others, but it
+is different from ``UUIDs'' found in FAT file systems, for instance.},
+like this:

When we implement FAT UUIDs, we’ll either adjust the ‘uuid’ form or
introduce a separate ‘fat-uuid’ form.

Thanks,
Ludo’.