DragonFlyBSD

It seems like you don't have a recognized MBR on 'ad0'.
Installing an initial MBR can be done by:
fdisk -BI ad0

Updating the MBR can be done by:
fdisk -u ad0

If you would like to have multiple OSs installed,
a boot manager can be installed in MBR by:
disklabel -B ad0

How did you try to modify MBR; using installer or manually?
If manually; which commands did you use?
(e.g.
dd if=/dev/zero of=/dev/ad0 bs=512 count=32
fdisk -BI ad0
dd if=/dev/zero of=/dev/ad0s1 bs=512 count=32
disklabel -w -B ad0s1 auto
disklabel -e ad0s1
as example in disklabel man page)

Are you sure the HD you would like to modify is 'ad0'?
'da0' is first AHCI / SCSI attached disk,
'da8' is first external disk (e.g. USB attached),
'ad0' is first ATA / SATA, non-AHCI attached disk.

Your logs show several disks, ad0, ad8 & da0, in system:
egrep '(ad|da)[[:digit:]]' DMESG
..
ad0: 238475MB <SAMSUNG HM251JJ 2AA00 00> at ata0-master UDMA33
ad0: 488397168 sectors [484521C/16H/63S] 16 sectors/interrupt 1 depth queue
ad0: invalid primary partition table: no magic
da0 at ahci0 bus 0 target 0 lun 0
da0: <SATA HITACHI HTS72201 DCDZ> Fixed Direct Access SCSI-4 device
da0: Serial Number 071103DP1D10DGG5YHJP
da0: 150.000MB/s transfers
da0: 152627MB (312581808 512 byte sectors: 255H 63S/T 19457C)
da0: type 0x27, start 2048, end = 13860863, size 13858816 : OK
da0: type 0x7, start 13865040, end = 312575759, size 298710720 : OK
da8 at umass-sim1 bus 1 target 0 lun 0
da8: <3System USB FlashDisk 1.00> Removable Direct Access SCSI-2 device
da8: 1.000MB/s transfers
da8: 15360MB (31457280 512 byte sectors: 255H 63S/T 1958C)
da8: type 0xc, start 63, end = 31455647, size 31455585 : OK
(da8:umass-sim1:1:0:0): lost device
(da8:umass-sim1:1:0:0): removing device entry
da8 at umass-sim0 bus 0 target 0 lun 0
da8: <3System USB FlashDisk 1.00> Removable Direct Access SCSI-2 device
da8: 40.000MB/s transfers
da8: 15360MB (31457280 512 byte sectors: 255H 63S/T 1958C)
da8: type 0xc, start 63, end = 31455647, size 31455585 : OK

A few typos in prev. message:
bootmanager .. 'disklabel -B ad0' -> 'boot0cfg -B ad0'

Your .. disks .. 'ad0, ad8 & da0' - 'ad0, da0 & da8'

Thomas Nikolajsen (via DragonFly issue tracker) wrote:

If you would like to have multiple OSs installed,
a boot manager can be installed in MBR by:
disklabel -B ad0

I think you mean
boot0cfg -B /dev/ad0

cheers
simon

Thomas Nikolajsen (via DragonFly issue tracker) wrote:

Thomas Nikolajsen <thomas.nikolajsen@mail.dk> added the comment:

It seems like you don't have a recognized MBR on 'ad0'.

Believe me: I have - dozen times. Rebooting between assuming the kernel
caches the current (empty) MBR, powering off the machine - and as I told,
using as well Linux and Windows XP to create a partition including a
filesystem on the disk: DragonFly see always the attached MBR - regardless
what I've done before.

Installing an initial MBR can be done by:
fdisk -BI ad0

Tried - because it's described in /README

Updating the MBR can be done by:
fdisk -u ad0

As in FreeBSD since ages (I'm FreeBSD user since 2000 or so ...)

If you would like to have multiple OSs installed,
a boot manager can be installed in MBR by:
disklabel -B ad0

How did you try to modify MBR; using installer or manually?

Both.

If manually; which commands did you use?
(e.g.
dd if=/dev/zero of=/dev/ad0 bs=512 count=32

I used "dd if=/dev/zero of=/dev/ad0 bs=32k count=16 (later I tried count=640)

fdisk -BI ad0
dd if=/dev/zero of=/dev/ad0s1 bs=512 count=32
disklabel -w -B ad0s1 auto
disklabel -e ad0s1
as example in disklabel man page)

Are you sure the HD you would like to modify is 'ad0'?
'da0' is first AHCI / SCSI attached disk,

da0 is the "internal" windows disk (seen by both NTFS partitions on it).

'da8' is first external disk (e.g. USB attached),

USB stick I used to copy the logs.

'ad0' is first ATA / SATA, non-AHCI attached disk.

The empty disk I want to use to put DragonFly BSD on it.

Your logs show several disks, ad0, ad8 & da0, in system:

I couldn't see anything in the dmesg log, but I thought a developer might do ...

Jens

Could you try booting with AHCI driver disabled (menu item at boot),
and test if this makes you able to modify MBR of your
<SAMSUNG HM251JJ 2AA00 00> disk (currently ad0).

If this doesn't succeed; could you try DragonFly/i386
(I see you are using DragonFly/amd64),
to see if this makes any diffference being able to modify MBR.

If still no success, try disabling AHCI using DragonFly/i386.