FreeBSD fdisk how to?

Unga unga888 at
Fri Jun 20 07:51:47 UTC 2008

Hi all

I need to partition a new 250GB SATA disk.

BIOS Auto calculated disk geometry shows:
parameters extracted from in-core disklabel are:
cylinders=119706 heads=16 sectors/track=255 (4080 blks/cyl)

That is, Total sectors=488400480

Since the C/H/S values are not compatible with FreeBSD fdisk, I recalculated them as:
Sectors/track: 63
Heads: 255

Cylinders = 488400480 / 16065
	  = 30401

I made a configfile as:
g c30401 h255 s63
p 1 165 63 488392002
a 1

I ran fdisk as follows:
fdisk -f configfile -itv /dev/ad2

I get following message:

******* Working on device /dev/ad2 *******
fdisk: invalid fdisk partition table found
fdisk: WARNING line 1: number of cylinders (30401) may be out-of-range
    (must be within 1-1024 for normal BIOS operation, unless the entire disk
    is dedicated to FreeBSD)
parameters extracted from in-core disklabel are:
cylinders=119705 heads=16 sectors/track=255 (4080 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=30401 heads=255 sectors/track=63 (16065 blks/cyl)

Information from DOS bootblock is:
1: sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
    start 63, size 488392002 (238472 Meg), flag 80 (active)
        beg: cyl 0/ head 1/ sector 1;
        end: cyl 704/ head 254/ sector 63

Now my questions:

1. Am I suppose to enter as c1024 instead of c30401, irrespective of the size of the disk?

2. Is it an error if I still enter as c30401?

3. Am I suppose to enter the c30401 h255 s63 values to the BIOS as user mode before run fdisk?

In case the way I use fdisk under FreeBSD is not correct, appreciate if you guys can point to some documentation. I followed the fdisk(8).

Many thanks in advance.

Kind regards


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