Interdata_v6/usr/doc/man/man8/boot.8

Find at most related files.
including files from this version of Unix. 
.th BOOT VIII
.de DS
.sp
.ne \\$1
.dt
.nf
.in +4
..
.de DE
.fi
.in -4
..
.sh NAME
boot - how to boot UNIX
.de pp
.s1
.ti -2
.ul 1
\\$1
.sp
..
.sh DESCRIPTION
UNIX is normally loaded by reading an
\fIa.out\fR-format
file from the root filesystem into memory.
This is done by the
.it uboot
bootstrap program, which can be loaded by the
LSU (Loader Storage Unit)
or from magtape.
.pp "Bootstrap Procedure From Disc"
.lp +6 4
1.	Make sure low-core device definitions are set up as
described below, and the console tty is online.
.ti -4
2.	Turn the LSU `enable' switch
.it on.
.ti -4
3.	Press the INI switch. A `?' prompt should appear on the console.
.ti -4
4.	If UNIX is to be started in single-user mode, enter the value
x'F618' into the display-panel switch register
(DTA F618 RUN).
.ti -4
5.	Type on the console the name of a file in the root directory
to be loaded
(normally \fBunix\fR).
.ti -4
6.	When UNIX is initialized, the amount of user memory available is
printed on the console.
In single-user mode, the console is automatically logged in as the
super-user and a `#' prompt appears;
otherwise, a
.it login
process is started on each terminal listed in the
.it /etc/ttys
file.
.ti -4
7.	Turn the LSU `enable' switch
.it off.
.ti -4
8.	If rebooting after a crash, use
.it icheck
to check file system integrity. Use
.it date
to set the date and time.
.i0
.pp "Low-Core Initialization for Disc Boot"
.DS 12
.ul 1
Address	Value		Meaning
78	10	console address
79	38	PALS `Command 2' to initialize console
7A	C7	boot disk address
7B	32	LSU disk type code (32:fixed 33:removable)
7C	B6	controller address
7D	F0	selch address
7E-7F	0000	OS/MT `file extension' for LSU
80-81	0000
82-83	100	PSW save area (any value >=100 is OK)
84-85	100	register save area
.DE
.pp "Loading uboot From Magtape"
.lp +6 4
1.	Set up '50 sequence' low-core definitions as described below.
.ti -4
2.	Mount the tape containing the
.it uboot
image on drive\ 0.
.ti -4
3.	Execute at location x'30'
(DTA 30 ADD RUN).
The tape moves and a `?' prompt should appear on the console.
.ti -4
4.	Follow steps 4-8 as for disk.
.i0
.pp "Low-Core Initialization for Tape Boot"
.DS 13
.ul 1
Address	Value		Meaning
30-33	0000 0050	illegal instruction new PSW

50-53	D500 0300	al   x'300'    load from tape
54-57	4300 0080	b    x'80'     branch to loaded program

78	85		magtape address
79	A1		magtape read command
7A-7D		as for disk boot
7E	10		console address
			(copied to x'78' by \fIuboot\fR)
7f	38		PALS `command 2' to initialize console
80-85		as for disk boot
.DE
.pp "How it Works"
The
.it uboot
program has been copied onto the disk (after the swap area) by the
.it mkboot
command.
.it mkboot
also initialized block\ 0 of the disk to look like an OS/MT `volume descriptor',
which the LSU uses to locate the
.it uboot
image.
If either of these areas has been corrupted, the LSU operation will fail
and no `?' prompt will appear;
.it uboot
must then be loaded from a backup disk or magtape.

Once loaded,
.it uboot
relocates itself to address x'20000', reads a filename from the console,
and searches for the file in the root directory.
If a disk I/0 error occurs,
.it uboot
goes into a one-instruction loop;
if the file is not found, it repeats the `?' prompt.
Otherwise, the file is read into core at address\ 0 (skipping the
.it a.out
header), and executed beginning at x'60'.
.pp "Alternate System Devices"
In case of hardware or other problems, UNIX can be loaded from a
removable backup disk or with a different console tty,
by changing the low-core device definitions.
Once the system is loaded, it may also need to be reconfigured
before it begins execution, by changing values in a fixed configuration
area in the UNIX kernel, described below.

To change the configuration area:
.lp +6 4
1.	Follow the normal bootstrap procedure,
but type the boot filename preceded by a hyphen
(e.g. \fB-unix\fR).
.ti -4
2.	\fIuboot\fR will load the file and then halt (WAIT light goes on).
.ti -4
3.	Use the display panel to patch configuration values in core
(DTA address ADD DTA hi-halfword WRT DTA lo-halfword WRT).
.ti -4
4.	Execute at x'60' (DTA 60 ADD RUN).
.i0

The new configuration values may later be patched
in the
.it a.out
file itself using
.it ddt.

.pp "UNIX Kernel Configuration Area"
.DS 11
.ul 2
Name	Address	Value		Meaning
		(fullword)
trmask	404	0	debugging trace mask
memtop	408	40000	maximum possible memory
consdev	40C	0	console device number (major/minor
			logical device - NOT address)
rootdev	410	1	root device number
swapdev	414	1	swap device number
swplo	814	1F40	location of swap area on disk
nswap	41C	640	size in blocks of swap area
.DE

N.B.: The values \fIconsdev\fR, \fIrootdev\fR and \fIswapdev\fR
are UNIX logical device numbers (not hardware addresses),
each consisting of a major and minor device number
in the low-order two bytes of the word.
For information on device numbers and PALS commands, see
dsk(IV), pals(IV).
.sh "SEE ALSO"
mkboot(VIII), icheck(VIII), dsk(IV), pals(IV)