howto check and solve disk geometry error under linux ?

['chris']

hi

On the second IDE disk I have both OS installed: linux and freeBSD.

fdisk from freeBSD shows the following error:

WARNING: A geometry of 38296/16/255 for ad1 is incorrect.Using a more likely geometry. If this geometry is incorrect or you are unsure as to whether or not it's correct, please consult the Hardware Guide in the Documentation submenu or use the (G)eometry command to change it now.
Remember: you need to enter whatever your BIOS thinks the geometry is!
For IDE, it's what you were told in the BIOS setup.
For SCSI, it's the translation mode your controller is using.
Do NOT use a ``physical geometry''.


Disk name: ad1 FDISK Partition Editor
DISK Geometry: 9726 cyls/255 heads/63 sectors = 156248190 sectors (76293MB)

Offset Size(ST) End Name PType Desc Subtype Flags

0 63 62 - 12 unused 0
63 51199092 51199154 ad1s1 8 freebsd 165
51199155 10490445 61689599 ad1s2 4 ext2fs 131
61689600 52420095 114109694 ad1s3 4 extended DOS, LBA 15
114109695 42138495 156248189 ad1s4 4 ext2fs 131
156248190 1810 156249999 - 12 unused 0

The following commands are supported (in upper or lower case):

A = Use Entire Disk G = set Drive Geometry C = Create Slice F = `DD' mode
D = Delete Slice Z = Toggle Size Units S = Set Bootable | = Wizard m.
T = Change Type U = Undo All Changes W = Write Changes

Use F1 or ? to get more help, arrow keys to select.


# fdisk
******* Working on device /dev/ad1 *******
parameters extracted from in-core disklabel are:
cylinders=38296 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=38296 heads=16 sectors/track=255 (4080 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
start 63, size 51199092 (24999 Meg), flag 80 (active)
beg: cyl 0/ head 1/ sector 1;
end: cyl 1023/ head 254/ sector 63
The data for partition 2 is:
sysid 131 (0x83),(Linux native)
start 51199155, size 10490445 (5122 Meg), flag 0
beg: cyl 1023/ head 254/ sector 63;
end: cyl 1023/ head 254/ sector 63
The data for partition 3 is:
sysid 15 (0x0f),(Extended DOS (LBA))
start 61689600, size 52420095 (25595 Meg), flag 0
beg: cyl 1023/ head 254/ sector 63;
end: cyl 1023/ head 254/ sector 63
The data for partition 4 is:
sysid 131 (0x83),(Linux native)
start 114109695, size 42138495 (20575 Meg), flag 0
beg: cyl 1023/ head 254/ sector 63;
end: cyl 1023/ head 254/ sector 63

howto solve this problem under linux ?

[Stuart Browne]

Umm, what's the error under linux?

[Bill Thorsteinson]

Check the BOIS configuration for this drive.
Some bioses default to 16 heads. On modern
drives it makes more sense to use 255 heads
and 63 sectors. Neither match the real
geometry of the drives any more.

The disk is partitioned based on 255 heads.

If the BIOS is set for 255 heads and you
still have the problem. Use the geometry
configuration in fdisk to change the head
count.