Re: extended partitions

Werner Almesberger (
Wed, 4 Oct 1995 08:18:58 +0100 (MET) wrote:
> In case it turns out that many people need this possibility
> to install lilo,

Assuming that about half of the 1'000'000 or so Linux users use LILO
and that 0.1% of them uses this particular setup, we already have
500 confused people. Now if 10% of them post their confusion to the
news ...

> (or teach lilo how to use /dev/hda,

Possible, but undesirable for maintainability reasons.

Partition handling code exists now in the kernel and in fdisk. At both
places, some bugs existed at some time, and the code may also evolve
e.g. to support new partitioning schemes. Since the code in LILO would
be used on a comparably infrequent basis, it would take quite a while for
bugs to show up. Also, since a bad write would be hard to distinguish
from some other failure to install LILO (bad geometry, etc.), but it
could damage a file system in some subtle way, this may mean to burry
time bombs.

Theodore Ts'o <> wrote:
> Out of curiosity, what's the scenario where you'd want to install LILO
> on the boot sector of the (raw) extended partition? Usually it's
> installed on the MBR, or in the boot sector of the linux partition.

For instance if the Linux FS partitions are not accessible for booting,
e.g. because they're on the second disk and you don't have any additional
boot loader, or if all Linux FS partitions begin beyond the 1024 sector
limit, or if all Linux FS partitions are logical partitions, or if your
system resides exclusively in UMSDOS partitions, or some mixture thereof,

Not really the most common scenarios, but something that might
conceivably happen to people running a mix of operating systems. (Or
those unlucky few who inherited some weird partitioning.) Using extended
partitions to boot from is surely not the conceptually cleanest idea,
but for those who need it it's usually far superior to the alternatives.

> If we really want to do allow it, we could just set the size of the raw
> extended partition to be 2 sectors (1 block), and mke2fs won't be able
> to make a partition on a partition that small.

That sounds like a rather clean solution.

> basically, I got tired of helping users recover from a completely
> trashed filesystem. :-(


Maybe the idea of having an integrated tool to do partitioning, mkfs,
and LILO setup should be revived ...

- Werner

P.S. Take everything I wrote with a grain of salt - it's early in the
morning and I just got a cold, so may brain may not work the way
it thinks it does ...

 / Werner Almesberger, DI-LRC,EPFL,CH /