I recall doing this under X dp4, just like under linux.
there is a file called the fstab you can edit to have
it load/mount on startup.

Otherwise it goes something like this:
for Ide drives: use "hda" for primary master, hdb for
primary slave, hdc secondary master....and on,
scsi disks are similar, but use "sda(b,c,d)"

Both IDE and SCSI require the partition it is on, as well
so just tack on the partition #.
So at a terminal window type in this for a single partition, primary slave drive:
mkdir /User/newdrive
mount /dev/hdb1 /User/newdrive
that is all.
Oh, sometimes, after mount <like for putting a pc hard-drive in your mac> you could use a "-t vfat".
Just a thought.

I also tried to do this, and worked hard to try to get it to work.
The problem is that the mounting is controlled by autodiskmount. anyway, I could get the computer to mount a partition or disk to a specific dirctory, but the finder would not recognize it. I did this by editing the /System/Library/StartupItems/Disks/Disks file, and the /etc/hostconfig file. anyway, I couldn't get it to work so that the finder would recognize it. There must be a way; this is a pretty simple UNIX feature, and maybe in the final release there'll be something that'll make it easier, or perhaps someone else will figure out a hack.

-rustychow