Dave Feustel wrote:
I got my 3.9 Cdrom set yesterday and today started installing
it on an external usb disk so as not to wipe out my existing
3.8 setup. When I got to the disk partition, I erased the existing
'a' partition (dos) and created a new bsd 'a' partition. The partition
had a default offset of 32 which looked odd to me, so I changed
it to 64 and sized it to 1G. Then I created a 'b' partition. Again,
the default offset was 32. That looked even odder to me, so
I aborted the installation. A dmesg of the 3.8 boot (with external
usb drive attached) follows at the end of this post.
So is it possible to install 3.9 on an external usb drive and then to
boot from that drive? Is the default 32 offset for a and b partitions
on the usb drive correct? (I don't think so, but I am asking anyways
since I have not used usb hard drives with OpenBSD before).
The point is not a 32 block or 63 block offset, but rather, a ONE TRACK
offset for the first partition on i386 and some other systems. This
leaves room for the master boot record (MBR) which is in sector 0.
Your dmesg showed this:
sd0 at scsibus2 targ 1 lun 0: <WDC WD60, 0UE-22HCT0, 0000> SCSI0 0/direct fixed
sd0: 57231MB, 57231 cyl, 64 head, 32 sec, 512 bytes/sec, 117210240 sec total
so the layout for this disk connected this way is 32 sectors per track
so YES, it should be starting at 32.
If you override this, you left a 32 sector gap at the beginning of the
disk, and disklabel will start looking for space at the start of the
disk, so again, it will offer you that same starting address.
Most modern IDE and SATA disks will use a track size of 63 sectors, so
yes, that's your offset. HOWEVER, if you were to bring OpenBSD up on an
old MFM drive, you would be looking at 17 sectors per track, so THAT
would be your offset.
Your disklabel offsets should match your fdisk offsets, though if you
answered "yes" to the "use entire disk" option, that was done for you in
the install program.
Can this all work? Certainly, assuming a machine that boots off an
external USB HD, but most new machines can. You can even set up the
disk with funny offsets if you take full responsibility for doing the
math accurately. :)
I would recommend disconnecting the "normal" disk from the machine for
testing, however. Keeps life easier...
Nick.
Nick.
