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Command: boot | Section: 8 | Source: UNIX v7 | File: boot.8
BOOT(8) System Manager's Manual BOOT(8)
NAME
boot - startup procedures
DESCRIPTION
A V7/x86 system is started by a two-stage process. The first is a pri-
mary bootstrap which is able to read in relatively small stand-alone
programs; the second (called boot) is used to read in the system it-
self. Both bootstraps are 16-bit x86 `real mode' programs in pure bi-
nary format.
The primary bootstrap must reside in the otherwise unused block zero of
the boot device, or block zero of the V7/x86 partition, in the case of
disks with `fdisk partitions'. This is loaded at address 0x7c00, ei-
ther by the ROM BIOS directly or by code loaded by the BIOS from the
master boot record of the disk. This program immediately loads the
second stage bootstrap at address 0x8000.
The second stage actually brings in the system. When executed, boot
types a prompt on the console as follows
BOOT [hd(0,0)unix]:
Then it reads from the console a device specification (see below) fol-
lowed immediately by a pathname. Boot finds the corresponding file on
the given device, loads that file into memory at address 0x10000, and
passes control to it.
Information displayed between square brackets constitutes defaults ob-
tainable by pressing the Enter key without further input. Where the
pathname specifies a directory, the contents is listed.
Conventionally, the name of the current version of the system is
`/unix'. Thus, the recipe is:
1) Load and execute boot by powering up, or rebooting, the machine
and selecting the V7/x86 partition, where applicable.
2) When the prompt is given, type
hd(0,0)unix
or
fd(0,0)unix
depending on whether you are loading from hard drive or from the
floppy drive, respectively. The first 0 indicates the physical
unit number; the second indicates the block number of the begin-
ning of the logical file system to be searched (see below). The
block number may be omitted, if zero.
When the system is running, it types a `#' prompt. After any file sys-
tem checks have been performed, a multi-user system is brought up by
typing an EOT (control-d) in response to the `#' prompt.
Device specifications. A device specification has the following form:
device(unit,offset)
where device is the type of the device to be searched, unit is the unit
number of the device, and offset is the block offset of the file system
on the device. Device is one of the following
hd hard drive
fd floppy drive
For example, the specification
hd(1,7000)
indicates a hard drive, unit 1, and the file system found starting at
block 7000.
FILES
/unix - system code
/usr/boot/pcuboot - copy of primary bootstrap
/boot - second stage bootstrap
SEE ALSO
init(8)
BOOT(8)