Re: GuixSD bootable ISO-9669 image

[ludo@gnu.org (Ludovic Courtès)]

Howdy,

Danny Milosavljevic <dannym@scratchpost.org> skribis:

> On Tue, 16 May 2017 10:31:36 +0200
> ludo@gnu.org (Ludovic Courtès) wrote:
>> Honestly, I was under the assumptions that DCE UUIDs was all that
>> mattered: it works for ext2 and btrfs, right?  I would think that people
>> would rarely add FAT32 or ISO9660 UUIDs to the OS config.  
>
> With UEFI I thought that everyone has at least one FAT32 UUID in the OS config?

I actually use the /dev device name but you’re right, we should be using
UUIDs in this case.

> What's more, just by checking /dev/disk/by-uuid the user wouldn't know what kind of filesystem it is.  But he had to specify the file system type in the config anyway - so it would be no worse than before.  Okay then.
>
> What do you all think of the following?
>
> (define %iso9660-uuid-rx
>   ;;                   Y                m                d                H                M                S                ss
>   (make-regexp "^([[:digit:]]{4})-([[:digit:]]{2})-([[:digit:]]{2})-([[:digit:]]{2})-([[:digit:]]{2})-([[:digit:]]{2})-([[:digit:]]{2})$"))
>
> (define (string->iso9660-uuid str)
>   "Parse STR as a ISO9660 UUID (which is really a timestamp - see /dev/disk/by-uuid).
> Return its contents as a 16-byte bytevector.  Return #f if STR is not a valid
> ISO9660 UUID representation."
>   (and=> (regexp-exec %iso9660-uuid-rx str)
>          (lambda (match)
>            (letrec-syntax ((match-numeral
>                             (syntax-rules ()
>                               ((_ index)
>                                (match:substring match index)))))
>              (let ((year (match-numeral 1))
>                    (month (match-numeral 2))
>                    (day (match-numeral 3))
>                    (hour (match-numeral 4))
>                    (minute (match-numeral 5))
>                    (second (match-numeral 6))
>                    (hundredths (match-numeral 7)))
>                (string->utf8 (string-append year
>                                             month
>                                             day
>                                             hour
>                                             minute
>                                             second
>                                             hundredths)))))))

LGTM!  Or even:

--8<---------------cut here---------------start------------->8---
(letrec-syntax ((match-numerals
                 (syntax-rules ()
                   ((_ index (name rest ...) body)
                    (let ((name (match:substring match index)))
                      (match-numerals (+ 1 index) (rest ...) body)))
                   ((_ index () body)
                    body))))
  (match-numerals 0 (year month day hour)
                  (string-append year month day)))
--8<---------------cut here---------------end--------------->8---

:-)

> And also:
>
> (define string->btrfs-uuid string->uid)
> (define string->ext2-uuid string->uid)
> (define string->ext3-uuid string->uid)
> ...

Yes, sounds reasonable.

Thanks!

Ludo’.