120 lines
3.3 KiB
Plaintext
120 lines
3.3 KiB
Plaintext
.\" $NetBSD: prep,v 1.12 2001/04/07 18:25:46 jhawk Exp $
|
|
.
|
|
First and foremost, before beginning the installation process,
|
|
.Em make sure you have a reliable backup
|
|
of any data on your hard disk that you
|
|
wish to keep. Mistakes in partitioning your hard disk may lead
|
|
to data loss.
|
|
.Pp
|
|
Before you begin, you should be aware of the geometry issues that may
|
|
arise in relation to your hard disk. First of all, you should know
|
|
about sector size. You can count on this to be 512 bytes; other sizes
|
|
are rare (and currently not supported). Of particular interest are
|
|
the number of sectors per track, the number of tracks per cylinder
|
|
(also known as the number of heads), and the number of cylinders.
|
|
Together they describe the disk geometry.
|
|
.Pp
|
|
The
|
|
.Tn BIOS
|
|
has a limit of 1024 cylinders and 63 sectors per track for
|
|
doing
|
|
.Tn BIOS
|
|
I/O. This is because of the old programming interface
|
|
to the
|
|
.Tn BIOS
|
|
that restricts these values. Most of the big disks
|
|
currently being used have more than 1024 real cylinders. Some have
|
|
more than 63 sectors per track. Therefore, the
|
|
.Tn BIOS
|
|
can be instructed
|
|
to use a fake geometry that accesses most of the disk and the fake
|
|
geometry has less than or equal to 1024 cylinders and less than or
|
|
equal to 63 sectors. This is possible because the disks can be
|
|
addressed in a way that is not restricted to these values, and the
|
|
.Tn BIOS
|
|
can internally perform a translation. This can be activated
|
|
in most modern BIOSes by using
|
|
.Em Large
|
|
or
|
|
.Em LBA
|
|
mode for the disk.
|
|
.Pp
|
|
.Nx
|
|
does not have the mentioned limitations with regard to the
|
|
geometry. However, since the
|
|
.Tn BIOS
|
|
has to be used during startup,
|
|
it is important to know about the geometry the
|
|
.Tn BIOS
|
|
uses. The
|
|
.Nx
|
|
kernel should be on a part of the disk where it can be loaded using the
|
|
.Tn BIOS ,
|
|
within the limitations of the
|
|
.Tn BIOS
|
|
geometry. The install program will check this for you, and
|
|
will give you a chance to correct this if this is not the case.
|
|
.Pp
|
|
If you have not yet installed any other systems on the hard disk
|
|
that you plan to install
|
|
.Nx
|
|
on, or if you plan to use the
|
|
disk entirely for
|
|
.Nx ,
|
|
you may wish to check your
|
|
.Tn BIOS
|
|
settings for the
|
|
.Sq Large
|
|
or
|
|
.Sq LBA
|
|
modes, and activate
|
|
them for the hard disk in question. While they are not needed
|
|
by
|
|
.Nx
|
|
as such, doing so will remove the limitations mentioned
|
|
above, and will avoid hassle should you wish to share the disk with
|
|
other systems. Do
|
|
.Em not
|
|
change these settings if you already have
|
|
data on the disk that you want to preserve!
|
|
.Pp
|
|
In any case, it is wise to check your the
|
|
.Tn BIOS
|
|
settings for the
|
|
hard disk geometry before beginning the installation, and write
|
|
them down. While this should usually not be needed, it enables
|
|
you to verify that the install program determines these values
|
|
correctly.
|
|
.Pp
|
|
The geometry that the
|
|
.Tn BIOS
|
|
uses will be referred to as the
|
|
.Tn Em BIOS
|
|
.Em geometry ,
|
|
the geometry that
|
|
.Nx
|
|
uses is the
|
|
.Em real geometry .
|
|
.Pp
|
|
.Ic sysinst ,
|
|
the
|
|
.Nx
|
|
installation program, will try to discover both the real geometry and
|
|
.Tn BIOS
|
|
geometry.
|
|
.Pp
|
|
It is
|
|
.Em important
|
|
that
|
|
.Ic sysinst
|
|
know the proper
|
|
.Tn BIOS
|
|
geometry to be able
|
|
to get
|
|
.Nx
|
|
to boot, regardless of where on your disk you put it.
|
|
It is less of a concern if the disk is going to be used entirely for
|
|
.Nx .
|
|
If you intend to have several OSes on your disk, this becomes
|
|
a much larger issue.
|