Aligning MBR for ZFS boot help

[Bruce Evans]

On Tue, 12 Mar 2013, Bruce Evans wrote:

> Last time I looked, Linux fdisk[s] worked better on FreeBSD than FreeBSD
> fdisk, partly because they don't depend on special ioctls, so that they
> know that they don't know the BIOS geometry.  Specifying the geometry is
> so routine that it is a command-line parameter in all Linux fdisks in
> FreeBSD ports (at least in old versions).

Just tried an old version of them on my version of an old version of
FreeBSD.  They worked not so well:

- fdisk-linux: worked OK except for bogus warnings about > 1024 cylinders
   and a not so bogus warning about a slice not ending on a cylinder
   boundary.  The slice just ends at the end of the disk, and since the
   cylinders are fake that happens not to be a cylinder boundary.  The
   disk has a firmware fake geometry of 63 sectors 16 heads and mumble
   cylinders, and the disk manufacturer throws away sectors at the end
   to make it end on a cylinder boundary with these fake cylinders, but
   I use different fake cylinders.  FreeBSD, Linux and WinXP don't care
   about the slice not ending on a cylinder boundary.
- sfdisk-linux: refused to start without write permission
- cfdisk-linux: refused to start due to 1 slice not ending on a cylinder
   boundary.  With its -z workaround for not starting, it starts but is
   useless since it doesn't display the existing partitions.

Bruce