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Re: FAQ bug

From: Andries . Brouwer
Subject: Re: FAQ bug
Date: Mon, 11 Feb 2002 11:07:39 GMT

    From address@hidden Mon Feb 11 05:45:55 2002

    > Maybe the authors of grub would like the world to be different,
    > perhaps that would have been more convenient to grub, but reality
    > is that the partition type does not indicate the filesystem.
    > Not only does that fail for Hurd, it fails all over the place.
    > For example, 0x83 is Linux (xiafs or ext2 or ext3 or reiserfs or ...).

    IMHO, what wants to make the world different is Linux. Partition types
    have been used as the FAQ entry says historically. Note that there is
    no reliable specification on how to use partition types (besides the
    "empty" type and those for extended partitions), so it just mentions
    the historical usage (and Linux doesn't follow the ambiguous rule).

    BTW, why that fails for Hurd? Be more specific, please.

    > So, anything that assumes a connection between partition type
    > and filesystem type is a bug, and in particular this FAQ entry
    > is a bug.

    Then, tell us where to see the specification.

I suppose you must know, but I have at


a description of the use of partition IDs as found in real life.
There is more stuff about partition tables there.

> Partition types have been used as the FAQ entry says historically.

Long ago an operating system had only one filesystem type,
so both points of view were indistinguishable. But not many
OSes used a partition ID to designate the type of filesystem.

This ID is used for all kinds of purposes:
2: XENIX root, 3: XENIX /usr
Here the ID gives the place where the fs is to be mounted.

6: 16-bit FAT, e: 16-bit FAT, LBA mapped
Here the ID indicates what BIOS calls should be used for access.

12: Compaq config partition
Here one has a FAT filesystem, but the ID is not 1, 4 or 6.
The ID indicates the function of the partition.

16: Hidden DOS 16-bit FAT.
42: Windows 2000 marker indicating a non-legacy partition table
55: EZ-Drive, a disk manager

Etc etc. You see that the general tendency is to indicate the
function of the partition, or some property of the partition,
and that only by coincidence sometimes the partition ID implies
a particular filesystem type.


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