[tlug] Re: Trouble with external USB hard disk: drive order; hard and optical drive names

[John Fremlin <john@example.com>]

Curt Sampson <cjs@example.com> writes:

> On 2008-10-22 10:43 +0100 (Wed), Godwin Stewart wrote:
>
>> On a (V)FAT filesystem, a volume label is technically a file on the
>> disk. The filesystem therefore has to be mounted already for the O/S
>> to know what the label is....
>
> Technically, not really, no; you could just read the raw device and
> interpret enough of the file system layout to get that one filename out
> of the root directory. Some programs (or, at least, some BSD programs)
> are already taking this approach just to figure out if there's really a
> vfat filesystem in that partition.

If you look at /dev/disk/by-label on recent Ubuntu you will see that
udev already links to FAT partitions there by label. It gets its info
from the vol_id program (also in the udev package).

(A label is stored in the FAT header for FAT12, FAT16 and FAT32 -- I
ought to remember because I implemented a full VFAT filesystem and VFS
layer from scratch in my last job.)

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