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. Something is very confused. I do not believe an existing 'a' partition (dos). What you really need is the disk geometry BEFORE you did whatever. The OpenBSD 'a' partition is the root. It needs to be bootable (id addressable) by the BIOS. It needs be be very small so that everything required for booting fits inside the limits of the BIOS. The BIOS likely uses CHS addressing. The exact limits depend on which BIOS and which disk geometry. Generally hard drives went to claiming 63 sectors per track very early to extend the limits. Since the disks are small and NOT usually boot devices there is not the need to use antiquated methods of extending addressable disk space. In that case, 32 sectors per track seems a very plausible number. It should make some internal addressing rather more readily calculable with stuff being powers of two.
Partitions labeled a,b,c etc belong to an OpenBSD disklabel. This is actually totally independent of what holds what are called DOS partitions (and I think these are numbered like 0,1,2,3 on OpenBSD. The > > 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 offset should be whatever the drive wants to claim. I think the number has to be somewhere between 1 and 63 and is really one less than the number of wasted sectors at the beginning of the disk. For some reason, Operating Systems seem to be unhappy unless they start at the beginning of the track they start on. An offset that is valid for one disk geometry is very wrong for a different disk geometry. Do not decide it looks funny just because it's a different disk. > sd0: 57231MB, 57231 cyl, 64 head, 32 sec, 512 bytes/sec, That is 32 sitting there.
