[src/trunk]: src/sbin/fdisk/mbr Add a manual page describing the MBR and the ...

[fvdl <fvdl%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/7f6b6ec69bbf
branches:  trunk
changeset: 471945:7f6b6ec69bbf
user:      fvdl <fvdl%NetBSD.org@localhost>
date:      Thu Apr 15 22:35:19 1999 +0000

description:
Add a manual page describing the MBR and the bootselector.

diffstat:

 sbin/fdisk/mbr/mbr.8 |  90 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 90 insertions(+), 0 deletions(-)

diffs (94 lines):

diff -r ced317c5837e -r 7f6b6ec69bbf sbin/fdisk/mbr/mbr.8
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/sbin/fdisk/mbr/mbr.8      Thu Apr 15 22:35:19 1999 +0000
@@ -0,0 +1,90 @@
+.\"    $NetBSD: mbr.8,v 1.1 1999/04/15 22:35:19 fvdl Exp $
+.Dd April 13, 1999
+.Dt MBR 8 i386
+.Os
+.Sh NAME
+.Nm mbr ,
+.Nm bootselect
+.Nd
+Master Boot Record bootcode
+.Sh DESCRIPTION
+A PC boots from a disk by loading its first sector and executing the code
+in it. For a hard disk, this first sector usually contains a table of
+partitions present on the disk. The first sector of a disk containing such
+a table is called the Master Boot Record (MBR). The code present in
+the MBR will typically examine the partition table, find the partition
+that is marked active, and boot from it. Booting from a partition simply
+means loading the first sector in that partition, and executing the
+code in it, as is done for the MBR itself.
+.Pp
+NetBSD supplies its two versions of the bootcode in an MBR:
+.Bl -tag -width Er
+.It Sy Normal boot code
+This version has the same functionality as that supplied by DOS/Windows and
+other operating systems: it picks the active partition and boots from it.
+Its advantage over other, older MBRs, is that it can detect and use
+extensions to the BIOS interface that will allow it to boot partitions
+that cross or start beyond the 8 Gigabyte boundary.
+.It Sy Bootselector
+The bootselecting MBR contains configurable code that will present
+the user with a simple menu, allowing a choice between partitions to
+boot from, and hard disks to boot from. The choices and default settings
+can be configured through fdisk(8).
+.El
+.Pp
+The rest of this manual page will discuss the bootselecting version of
+the MBR. The configurable items of the bootselector are:
+.Bl -tag -width Er
+.It timeout
+The number of seconds that the bootcode will wait for the user to
+press a key, selecting a menu item. Must be in the range 0-3600.
+.It default
+The default partition or disk to boot from, should the timeout
+expire.
+
+.It active
+Activate/deactivate the bootselector. When deactivated, the
+bootcode will pick the first active partition, as usual.
+.El
+
+.Pp
+When active, the bootselector will let the user select the partition
+or drive to boot from via the keyboard. Keys F1 through F4 will
+initiate a startup from partitions 1 through 4 in the partition table,
+if the corresponding entries in the bootselector menu are active.
+.Pp
+Keys F5 through F10 will boot from harddisks 0 through 5 (BIOS numbers
+0x80 through 0x85). Booting from a drive is simply done by reading
+the MBR of that drive and executing it, so the bootcode present in
+the MBR of the chosen drive determines which partition (if any) will
+be booted in the end.
+.Pp
+The Enter key will cause the bootcode to find the active partition,
+and boot from it. If no key is pressed, the (configurable) default
+selection is picked.
+
+.Sh DIAGNOSTIC
+The following messages may be printed in case of an error condition,
+(after which the user must restart the system):
+.Bl -tag -width Er
+.It Error 1
+Invalid partition table. The MBR has a partition table without an
+active partition.
+.It Error 2
+Read error. There was an error reading the bootsector for the
+partition or drive selected.
+.It Error 3
+No operating system. The bootsector was loaded successfully, but
+it was not valid (i.e. the magic number check failed).
+.El
+
+.Sh SEE ALSO
+.Xr fdisk 8
+.Sh BUGS
+The bootselect code has constraints because of the limited amount of
+space available. The only way to be absolutely sure that a bootselector
+will always fit on the disk when a partition table is used, is to make
+it small enough to fit into the first sector (512 bytes, 446 not counting
+the partition table itself). The error messages are short. The code
+will give up if an error occurs, it should allow the user to, for example,
+specify another partition/disk instead.