Aren/NetBSD
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Document the new checks for whether a PBR is bootable.

Browse Source 
Also add more detail in the introduction, and a few
more references.
This commit is contained in:
apb 2007-03-10 14:19:46 +00:00
parent 4c9d64d78e
commit 7a268741a3
1 changed files with 67 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

76
sbin/fdisk/fdisk.8
View File

@ -1,4 +1,4 @@
.\" $NetBSD: fdisk.8,v 1.53 2006/09/24 15:52:12 wiz Exp $
.\" $NetBSD: fdisk.8,v 1.54 2007/03/10 14:19:46 apb Exp $
.\"
.Dd September 24, 2006
.Dt FDISK 8
@ -41,12 +41,36 @@
.Sh DESCRIPTION
The
.Nm
program is used to divide space on a disk into partitions and set
one active.
program is used to display or update the
.Em "master boot record"
or
.Em MBR
in the first sector (sector 0)
of a disk that uses the MBR style of partitioning.
The following
.Nx
ports use this style of disk partitioning:
amd64, arc, bebox, cobalt, hpcarm, hpcmips, hpcsh, i386, macppc,
mvmeppc, netwinder, ofppc, playstation2, and prep.
.Pp
The MBR contains bootable code, a partition table,
an indication of which partition is
.Sq active ,
and (optionally, depending on the boot code) a menu
for selecting a partition to be booted.
There can be at most 4 partitions defined in sector 0,
one of which can be an extended
partition which can be split into any number of sub-partitions.
.Pp
The boot code in the MBR is usually invoked by the BIOS or firmware,
and the MBR passes control to the next stage boot code
stored in the first sector of the partition to be booted
(the
.Em "partition boot record"
or
.Em PBR ) .
.Pp
After booting,
.Nx
does not use the partitioning done by
.Nm ,
@ -55,6 +79,12 @@ instead it uses a
disklabel saved in sector 1 of the
.Nx
partition.
See
.Xr mbrlabel 8
for a way of using information from the MBR
to construct a
.Nx
disklabel.
.Pp
The standard MBR boot code will only boot the
.Sq active
@ -412,7 +442,8 @@ is output if this is the active partition.
.Pp
If the
.Fl v
flag is given two additional lines are output for each partition:
flag is specified, the beginning and end of each partition is also
displayed as follows:
.in +4
beg: cylinder
.Em cylinder ,
@ -441,14 +472,39 @@ these numbers are read from the bootblock, so are the values calculated
by a previous run of
.Nm .
.El
.Pp
.Nm
attempts to check whether each partition is bootable,
by checking the magic number and some other characteristics
of the first sector of each partition (the PBR).
If the partition does not apear to be bootable,
.Nm
will print a line containing
.Dq "PBR is not bootable"
followed by an error message.
If the partition is bootable, and if the
.Fl v
flag is specified,
.Nm
will print
.Dq "PBR appears to be bootable" .
If the
.Fl v
flag is specified more than once,
.Nm
will print the heading
.Dq "Information from PBR:"
followed by one or more lines of information gleaned from the PBR;
this additional information may be incorrect or misleading,
because different operating systems use different PBR formats.
Note that, even if no errors are reported, an attempt to boot
from the partition might fail.
.Nx
partitions may be made bootable using
.Xr installboot 8 .
.Sh NOTES
This program is only available (and useful) on systems with PC-platform-style
MBR partitioning.
On
.Nx
this includes the following ports: amd64, arc, bebox, cobalt, hpcarm,
hpcmips, hpcsh, i386, macppc, mvmeppc, netwinder, ofppc, playstation2,
and prep.
.Pp
Traditionally the partition boundaries should be on cylinder boundaries
using the BIOS geometry, all of the first track should be reserved
@ -496,7 +552,9 @@ Default location of i386 bootselect for extended partitions
.El
.Sh SEE ALSO
.Xr disktab 5 ,
.Xr boot 8 ,
.Xr disklabel 8 ,
.Xr installboot 8 ,
.Xr mbr 8 ,
.Xr mbrlabel 8
.Sh BUGS