.TH REBOOT 8 "10 May 1981"
.UC 4
.SH NAME
reboot \- UNIX bootstrapping procedures
.SH SYNOPSIS
.B /etc/reboot
[
.B \-n
] [
.B \-q
]
.SH DESCRIPTION
.PP
UNIX is started by placing it in memory
at location zero and transferring to zero.
Since the system is not reenterable,
it is necessary to read it in from disk or tape
each time it is to be bootstrapped.
.PP
.B Rebooting a running system.
When a UNIX is running and a reboot is desired,
.IR shutdown (8)
is normally used.
If there are no users then
.B /etc/reboot
can be used.
Reboot causes the disks to be synced, and then a multi-user
reboot (as described below) is initiated.  This causes a system to be
booted and an automatic disk check to be performed.  If all this succeeds
without incident, the system is then brought up for many users.
.PP
Options to reboot are:
.TP
.B \-n
option avoids the sync.  It can be used if a disk or the processor
is on fire.  (It is no longer necessary to reboot after rebuilding
the root file system.)
.TP
.B \-q
reboots quickly and ungracefully, without shutting down running
processes first.
.PP
.B "Power fail and crash recovery."
Normally, the system will reboot itself at power-up or after crashes.
Provided the auto-restart is enabled on the machine front panel,
an automatic consistency check of the file systems will be performed
then and unless this fails the system will resume multi-user operations.
.PP
.B Cold starts.
These are processor type dependent.
On an 11/780, there are two floppy files for each disk controller,
both of which cause boots from unit 0 of the root file system
of a controller located on mba0 or uba0.
One gives a single user shell, while the other invokes the multi-user
automatic reboot.  Thus these files are HPS and HPM for the single
and multi-user boot from MASSBUS RP06/RM03/RM05 disks,
UPS and UPM for UNIBUS storage module controller and disks
such as the EMULEX SC-21
and AMPEX 9300 pair, or HKS and HKM for RK07 disks.
.PP
Giving the command
.IP
>>>BOOT HPM
.LP
Would boot the system from (e.g.) an RP06 and run the automatic consistency
check as described in
.IR fsck (8).
(Note that it may
be necessary to type control-P
to gain the attention of the LSI-11 before getting the >>> prompt.)
The command
.IP
>>>BOOT ANY
.LP
invokes a version of the boot program in a way which allows you to
specify any system as the system to be booted.
It reads from the console a device specification (see below) followed
immediately by a pathname.
.PP
On an 11/750, the reset button will boot from the device
selected by the front panel boot device switch.  In systems
with RK07's, position B normally selects the RK07 for boot.
This will boot multi-user.  To boot from RK07 with boot flags you
may specify
.IP
>>>B/\fIn\fR DMA0
.LP
where, giving a \fIn\fR of 1 causes the boot program
to ask for the name of the system to be bootstrapped,
giving a \fIn\fR of 2 causes the boot program to come up single
user, and a \fIn\fR of 3 causes both of these actions to occur.
.PP
The 11/750 boot procedure uses the boot roms to load block 0 off of
the specified device.  The /usr/mdec directory contains a number
of bootstrap programs for the various disks which should be placed
in a new pack automatically by
.IR newfs (8)
when the ``a'' partition file system on the pack is created.
.PP
On both processors, the 
.I boot
program
finds the corresponding file on the given device, loads that file
into memory location zero, and starts the program at the entry address
specified in the program header (after clearing off the high bit
of the specified entry address.)
Normal line editing characters can be used in specifying the pathname.
.PP
If you have a MASSBUS disk
and wish to boot off of a file
system which starts at cylinder 0
of unit 0, you can type \*(lqhp(0,0)vmunix\*(rq
to the boot prompt; \*(lqup(0,0)vmunix\*(rq would specify
a UNIBUS drive, ``hk(0,0)vmunix'' would specify
an RK07 disk drive, ``ra(0,0)vmunix'' would specify a
UDA50 disk drive, and ``rb(0,0)vmunix'' would specify a
disk on a 730 IDC.
.PP
A device specification has the following form:
.IP
device(unit, minor)
.PP
where
.I device
is the type of the device to be searched,
.I unit
is 8* the mba or uba number plus
the unit number of the device,
and
.I minor
is the minor device index.
The following list of supported devices may vary from installation to
installation:
.ta 5 10
.nf
	hp	MASSBUS disk drive
	up	UNIBUS storage module drive
	ht	TE16,TU45,TU77 on MASSBUS
	mt	TU78 on MASSBUS
	hk	RK07 on UNIBUS
	ra	storage module on a UDA50
	rb	storage module on a 730 IDC
	tm	TM11 emulation tape drives on UNIBUS
	ts	TS11 on UNIBUS
	ut	UNIBUS TU45 emulator
.fi
.PP
For tapes, the minor device number gives a file offset.
.PP
In an emergency, the bootstrap methods described in the paper
``Installing and Operating 4.2bsd'' can be used
to boot from a distribution tape.
.SH FILES
.ta \w'/usr/mdec/mboot   'u
/vmunix	system code
.br
/boot	system bootstrap
.SH "SEE ALSO"
crash(8),
fsck(8),
init(8),
rc(8),
shutdown(8),
halt(8),
newfs(8)